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a pdf version of my final report

1. theCanvas GolfEngine Map Flag Ball GolfCanvas Player Look Left rotateView angle gt translateMap 7 A __ translate translate translateBall 1 translate drawScene A lt nage fom new When the user changes the values for E power sidespin and backspin nothing is New Display changed immediately The values of the scrollbars will be read when it comes to actually taking the shot Figure 15 3 1 Sequence diagram for the player selecting their shot 65 Aspects of Realism Golf Simulation Matthew Winchester This sequence diagram shows the process of calculating the flight of the ball This is repeated over and over until the ball contacts the ground where it wil either bounce or begin rolling theCanvas theEngine totalForce flightAffectors 0 flightAffectors 1 flightAffectors 2 theBall Ball GolfCanvas GolfEngine Force Gravity Drag Swerve travel create 0 0 0 al affect ityF le __ gravity Force addForce gravtyForc 1 gl affect dragr 7 le ragForce addForce dragForce affect Fi le swerveForce addForce swerveForce calculate physics gt Set new position Set new velocity Set new spin Figure 15 3 2 S
2. Ball GolfEngine xPos double numFlightAffectors int yPos double numPollAffectors int zPos double xAngle double Drag Vel double y Angle double yVel double zAngle double 2 Vel double numClubs int ee affect top_backSpin double currClub int FlightAffector left_rightSpin double a Gravity stopped boolean GolfEngine ightAffectors atfect AA inFlight boolean reset A affect E int Bibel lastDist double A etBall theEngine oetMap Swerve Ball theBall setBall setVelocity setWind affect setSpin translateMap hitBall translateBall an Friction x drawScene ey hitBall S p atfect 20 r ah nit rollAffectors RollAffector spee vi etNextClul x hasStopped getPrevClub atfect Alesis resetPolyCount bisPutted gt translate Fi getDistanceToPin affect drawP olygon a rotateView f setEngine P alterwind Ay thewlnd Sip storePos getWind Wind clubs A GolfClub Force pS ae affect eminVert double xComponent double Magnitude double maxVert double yComponent double angle double minHoriz double 42 Component double maxHoriz double Wind edeviation double Force refresh Force alter GolfClub addForce hitBall Figure 15 1 3 Class diagram showing the design for the implementation of physics NB The FlightAffecto
3. Aspects of Realism Golf Simulation Matthew Winchester 14 Ball Travel Algorithms The development of the algorithms needed to realistically model the flight of the ball is one of the most complex parts of this project For this reason I have created a separate application as a test bed for these algorithms 14 1 Data Structure The data structures I have designed to enable the implementation of these algorithms is shown in fig 14 1 1 The way that the different affecting factors are accounted for is by having a separate class for each these being the Drag Swerve and Gravity classes The affect method of these classes returns a Force object all the forces returned are combined to discover the resultant force on the ball The actual equations involved are those defined in chapter 6 Research Ball Flight DoublePoint x double GolfEngine wind y double numAffectors int A DoublePoint GolfEngine travel void yetBall Ball ts CN setBall newBall Ball void E FlightAffector setWind x double z double void theBall atfect theBall Ball wind DoublePoint Force A Ball Drag Gravity xPos double yPos double affect zPos double alert atfect xVel double yVel double zVel double top_backSpin double s E double Force stopped boolean a palate xComponent double sinFlight boolean y Compo
4. Figure 15 3 3 Sequence Diagram showing the 3D scene translation 67 Aspects of Realism Golf Simulation Matthew Winchester theCanvas theEngine rootNode GolfCanvas GolfEngine PolygonTreeNode leftNode PolygonTreeNode rightNode theMap Map theFlag Flag PolygonTreeNode drawScene draw draw drawPolygon index drawPolygon index draw o rawPolygon index 2 This sequence diagram shows the messages sent in the draing of a very simple scene In this case there are 3 polygons in the scene 2 polygons from the Map in the background and 1 polygon from the flag in the foreground The tree draws the scene one polygon per node by calling the source of that polygon and passing it the index of the polygon Figure 15 3 4 Sequence diagram showing the drawing of a scene Player Take Shot theCanvas theEngine clubs currClub theBall Ball GolfCanvas GolfEngine GolfClub hitBall power sidespin backspin hitBall theBall power angle setVelocity x y Z setSpin side back This sequence diagram shows the sequence of messages involved in hitting the ball It shows that the res
5. Ball flight 1 week Map display 1 week Ball bounce and roll 1 week Game 3D Engine 2 weeks Map view 2 weeks Ball travel 1 week Golf clubs 0 5 weeks Objects 1 weeks Game rules 2 weeks Testing and correction 2 weeks Technical documentation 1 weeks User manual 1 week Total 32 5 weeks Figure 3 2 1 Time estimations for all planned project stages The purpose of these time estimations is to help me to organise the sequence that I will follow whilst I am working through this project It is also useful in identifying areas that may be too complex This may be due to having over complicated your project in which case your 10 Aspects of Realism Golf Simulation Matthew Winchester project and hence the plan would have to be amended I have made one major change to my plan for this project since the proposal that is that I will not be using the rational unified process during this project The reason for this is that I feel it will overcomplicate this project and the control that it offers is overshadowed by the amount of extra time it will take 3 3 Milestones Milestones represent significant steps towards the completion of a project They also act as a short term target to aim for The state of a project can be very quickly found be assessing the progression of completed milestones The milestones that I have identified for this project are as follows M1 Research completed M2 Ready for design Research Requirements and Risk
6. amp Right Back amp Left Backward amp Left As you can see sidespin alone causes very little force until it is combined with topspin or backspin One very important fact however is the fact that spin is very quickly lost when sliding rolling across a surface with relatively high resistance such as a golf course The spin on the ball very quickly gets turned into topspin causing the ball to roll rather than slide 31 Aspects of Realism Golf Simulation Matthew Winchester 7 Research Golf Clubs The key to getting a shot right is in choosing the right club To implement a realistic way to simulate the effects of different types of golf club I need to investigate what types of club there are and what the differences between them are I will also take a look at why you might choose different clubs in different circumstances so that the computer could make a good guess at what club to automatically suggest 7 1 Types of Club There are 4 main classes of club These are Wood Iron Wedges and Putters 7 1 1 Wood The wood clubs have a very flat face They are used usually to tee off because they make the ball travel the furthest They are available in a number of flavours usually from 1 Wood up to 5 Wood The lower the number the flatter the face of the club see fig 7 1 1 and hence the further it can drive the ball The 1 Wood is more often referred to as The Driver Woods in general produce between 8 and 12 degrees
7. much longer handle to enable a different grip this has no effect on the ball other than giving the player a more comfortable or accurate swing NB They are actually used for putting Wood Driver Iron Wedge Putter Figure 7 1 1 Rough representation of the different profiles of Golf Clubs 7 2 Effect on Ball Table 7 2 1 shows a guide as to how far different clubs can hit the ball Obviously it depends greatly on the ability of the player and on a whole plethora of other factors it is however only intended as a rough guide 33 Aspects of Realism Golf Simulation Matthew Winchester Type of club Average distance of full swing Driver 1 Wood 200 220 mtrs 3 Wood 180 200 mtrs 5 Wood 170 190 mtrs 3 Iron 175 185 mtrs 4 Iron 155 165 mtrs 5 Iron 145 155 mtrs 6 Iron 135 145 mtrs 7 Iron 125 135 mtrs 8 Iron 115 125 mtrs 9 Tron 105 115 mtrs Pitching Wedge 85 100 mtrs Sand Wedge 65 85 mtrs Table 7 2 1 Average ball travel distances caused by a range of Golf Clubs 7 3 When to use which club The main issue to consider when choosing a club is the distance from the ball to the hole The information in Table 7 2 1 gives a rough guide as to which club corresponds to which distance However there are a few more factors to consider than that The lie of the ball is also very important For example if the ball is in heavy rough surrounded by long grass you would not use a driver to hit it What you should do is to
8. the structure represents a 3D sine wave rather than simply being random The main change needed to go from wire frame to filled was that the drawing order had to be correct This means drawing the polygons from the back to the front using a simplified Painter s algorithm The formula to create this 3D sinewave effect is as follows pointHeight 25 Math sin Math sqrt 3 3 WIDTH WIDTH L i WIDTH WIDTH 60 This dissects as follows J 3 WIDTH WIDTH distance in z direction squares z 1 i WIDTH WIDTH distance in x direction squares x Math sqrt z x distance of the point from the origin dist Math sin dist 100 a value between 1 and 1 that creates the wave effect over distance initialHeight PointHeight 25 initialHeight exaggerated sine wave higher waves Although the finished golf course is not going to be a 3D sinewave this way of creating the contour with formulae will be very useful when it comes to creating the actual course Figure 13 2 1 Screenshot of Map Representation vO La 53 Aspects of Realism Golf Simulation Matthew Winchester Figure 13 2 2 Screenshot of Map Representation vO 1b Fig 13 2 3 shows version 0 2 There is one major difference in this version This is that the colour of the polygons is now dependant on the angle that they are facing To accomplish this Calculat
9. viewpoint This involves taking the position AND the direction of the viewpoint into consideration This is the stage where any hidden surfaces are removed Screen Space This is the final stage of the process All of the objects within the view space is translated into 2D screen coordinates ready to be drawn This stage is where clipping will happen to prevent objects outside of the viewable area being drawn Figure 8 2 1 The basic graphics pipeline The graphics pipeline will vary depending on the various features of the engine in question For example if the engine implements Z Buffering a hidden surface removal method then there will be an extra stage between view and screen space for the Depth Buffered Screen Space 8 3 Major issues You could write a whole book on the building of 3D engines in fact many people have Because of this I am going to concentrate on the major issues that affect the building of a 3D engine 8 3 1 Accuracy v Speed Blinn 1979 discusses the major concern when building a 3D engine speed Creating very complex 2D images from 3D data is can be a very complex and time consuming process The more fancy effects that are implemented the slower the rendering time is It is for this reason that trade offs must be made To decide what effects should and should not be implemented you need to look at the purpose for the engine If you need a very fas
10. would make a Real Time 3D engine incredibly slow Aspects of Realism Golf Simulation Matthew Winchester 4 2 Freeform polygonal mesh Polygonal meshes are the most commonly used method of representing three dimensional objects They are composed of multiple flat polygons arranged in such a way as to approximate the shape they are representing Polygons are perfect for representing flat objects such as doors and walls Curved objects such as spheres can only be roughly approximated The accuracy of a curve represented by polygons depends on the number and size of the polygons Figure 4 2 1 shows how the frequency of polygons can affect the accuracy of the shape 141 788 polygons 35 305 polygons Figure 4 2 1 Showing how the frequency of polygons affects the accuracy of the representation Taken from 3D Computer Graphics by Alan Watt It seems fairly obvious that the more polygons the more accurate the shape This is absolutely true however the more polygons the more complex the object is This makes the modelling manoeuvring and representing of this object much more time consuming with more complex objects The decision on how complex to make your object is not a straight forward one and may involve striking a happy medium There are also ways to make less complex 15 Aspects of Realism Golf Simulation Matthew Winchester objects look more realistic Texture mapping allows simplified and rough polygonal objects
11. 6 show the breakdown of the work that needs to be done in order to complete this project Figure 3 1 1 is the head of this structure with the rest being extensions of it The reason for these diagrams is to enable me to plan the stages that the project will go through In the majority of information systems development cycles a major part of the project is the analysis and the modelling of the data and practices of the system they will be implemented to support or replace It is evident from the above diagrams that I have skipped past that phase This is because I am not replacing or supporting any established system I am simulating a real world situation This means that there is no modelling to do because all the information required will be gathered from the research Aspects of Realism Golf Simulation Matthew Winchester 3 2 Time Estimation The next step in creating a good project plan is to estimate how long each of the tasks I have identified will take Figure 3 2 1 shows the time I have allotted to each low level task Activity Estimated Duration Research Map Contour 1 weeks Map Texture 1 weeks Object Representation 1 week Ball Travel 1 weeks Golf Clubs 0 5 weeks 3D display engines 1 weeks Requirements Elicitation 2 weeks Analysis and validation 1 week Risk 1 week Design Data structures 3 weeks Class Diagrams 1 week Sequence state diagrams 2 weeks Tester App 2D views 0 5 weeks 3D view 1 week
12. NY A Rs Be Dal da 48 PAD A eR On Aer 207 Sone aE eer Sore oer ene ee a rT er ee 48 R4 2 User Inter ate A ES Und 48 EDE AI S EA EAE EA A a e e e de de le e a a o e ca 49 RO DOCUMENTATION oui ci sss cisbdaccceccasyescvsbinenaevebegsboetecdcnnvevetecessvacuebeveyessaeviueeceetecedashevoesaevees 49 TQ IRIS OT 51 Aspects of Realism Golf Simulation Matthew Winchester 13 MAP MODELLING AND REPRESENTA TION uuu ccccccccccccrcccescsscscsssssscsssssssscceees 52 13 1 MAP REPRESENTATION ccccccccccccecssssssseceececececccccccccccesssssseseseseeseeeceececcesececessssseeeesecs 52 132 MAP DISPLAY r n fe ios 52 14 BALL TRAVEL ALGORITHMS ccccccccsccsssccssccccssscsssssssssssssscccscceesssssscsscscossceess 58 14s DATA STRUCTURE inad a Gates a e a ERAN 58 14 2 THE APEC Ne A 59 ISEDESIGN TEATA A A A E APANE A A AREN 60 15 1 CLASS AND OBJECT DIAGRAMG cccccccssscccccccessseccccsescccsccessseccecssaaccceccessaeaccsseeesseeeecs 60 1522 STATE CHAR TS daa 64 13 3 SEQUENCE DIAGRA MS cits EE E lela Wa Sec ahaeviasooeslelalgeonoseateleese 65 16 TESTPRAN sissdsssceicdascceuesseeesasleacecaaaestccecaseseseesectaseeecscccancsadcteasesavesesdees E RE EAT 69 17 GAME IMPLEMENTATION ossseessooeoooooosssossssssssoososooosooossssosssseossosssosssoooesoossssossossosssos 70 17 1 CODING STANDARDS 22h O EA e iis 70 17 1 1 Naming Conventions soesssessssessseeesssesesssressresessressserssesresseetereressressseeeseseessreresseesssee 7
13. an image This is achieved by tracing the line between any world point and the viewpoint The 2D screen coordinate is calculated by finding where this line intersects a given plane the screen or image plane See Fig 8 1 1 for a diagrammatic representation Figure 8 1 1 A depiction of the basic 3D engine theory Translating from 3D to 2D is not all that must be considered The 3D description of the world itself must also be moved or rotated to bring life to your scenes and also to enable the viewpoint to be changed in both position and direction The basic steps that have to be followed are described as The Graphics Pipeline 8 2 The graphics pipeline The graphics pipeline is so called because it is a series of stages where the output of one stage becomes the input to the next The basic stages are shown in fig 8 2 1 35 Aspects of Realism Golf Simulation Matthew Winchester Object Space Coordinates for each object are held relative to some local origin usually the centre of the object This enables objects to be rotated and moved very easily World Space The coordinates for the objects have been translated to be relative to a global origin This places objects in position relative to each other and builds the scene This is the stage where any object movements will happen View Space Each object and coordinate within the scene is translated to be relative to the
14. be automatically selected for the user R4 Display R4 1 3D Engine Code Description Priority Notes 4 1 1 The 3D engine should allow the golf course to be viewed from any specified view position and direction 5 The contours of the map must be visible This can be implemented by simple shading See Chapter 5 section 6 The different textures of the golf course should be visible This can be implemented by simply having different colours for the different texture types The engine should generate a scene in a reasonable time This time should be as quick as possible but must be at most 1 second R4 2 User Interface Code Description Priority Notes 4 2 1 The user interface must be easy to understand 5 4 2 2 The required user input must be as simple as possible I e the user should not have to hold down Ctrl Alt Shift S just to take a shot 5 4 2 3 The user interface must be very responsive I e when the user does something it should be instantly noticeable so that the user knows their input has been accepted 48 Aspects of Realism Golf Simulation Matthew Winchester 4 2 4 The user must be able to select the golf club that they want to use They must also be able to change their mind and select a different club 4 2 5 The display should let the user know how far the ball is expecte
15. depending on the orientation of the surface This results in the shape of the object being visible as object b shows without any light shading the shape of the object is completely lost a Light Shaded b Solid Colour Figure 5 1 1 Showing the need for light shading There are various light shading methods that can be implemented The most simple is as shown above where each polygon is given a solid colour this is sometimes referred to by many names most usually though it is Face or Facet shading This is a very fast method and is very effective for shapes with flat surfaces such as acube However for curved surfaces where the polygons are used to approximate the curve this method produces unrealistic results with very bold lines between polygons To account for this there are alternative more complex shading algorithms available The most popular of which are Gouraud shading and Phong shading The basic idea behind both of these is to calculate the colour at the vertices of each polygon and then vary the colour across the polygon so that you get smooth transitions between vertices What this means is that adjoining polygons which share vertices between them will be shaded smoothly from one into the other thus eradicating the obvious differences between adjoining polygons and producing a smooth curved effect Fig 5 1 2 shows a comparison between Gouraud and Phong shading 20 Aspects of Realism Golf Simulation Matthew Winch
16. design can be object oriented too 1 5 Project Plan My plan for the project so far is as follows 1 Requirements Analyse the situation Extract Use Cases and Scenario s Draw up rough scripts and storyboards of selected processes Use the data I have found and the processes that I have uncovered to formulate the requirements Validate the requirements 2 Risk analysis Analyse the requirements to see what risks there are to the development process and prepare workarounds suggest preventative measures and prepare altrenative plans 3 Design Complete a system design based upon the validated requirements that I have produced 4 Implementation amp Testing Implement the design in java testing as I go 5 Deployment Get several different people to use the game and gather feedback 1 6 Resource Requirements As this project is going to be implemented in java there is no particular type of machine or operating system that is required I have a home computer Pentium 2 350Mhz 128MB RAM 17GB HD which I can use if I wish I also have a laptop Pentium 3 700Mhz 128MB RAM 12GB HD which I can use both to develop on and to demonstrate on 85 Aspects of Realism Golf Simulation Matthew Winchester 1 7 Keywords 3d engine modelling and representation aspects of realism golf game projectile simulation 86 Aspects of Realism Golf Simulation Matthew Winchester Appendix B User Guide 1 Running the simulation There
17. of GUIs Sequence diagrams also help in the designing of algorithms I am going to investigate the use of the Rational Unified Process using Rational s Requisite Pro I think this could be very useful because UML isn t a complete methodology for development it is only a modelling language Rational Unified Process is a complete methodology and could help a lot in the development of this project I have a plan to help me in the development of the algorithms and equations needed to implement the simulations I am going to build a tester application that displays a 3d world in flat 2d from 3 different angles top front and side this will allow me to trace the flight of the ball and see the effects that various factors have on the flight It can also be used in the building of the various courses When I get around to developing the 3d engine I will also build in a 4 view into the tester the 3d view This will enable me to make sure that the 3d engine is producing a realistic representation and that it ties in with the other 3 views Figure 1 4 1 shows my idea for a tester application 3D eventuall Figure 1 4 1 Rough idea for 3D tester 84 Aspects of Realism Golf Simulation Matthew Winchester I plan to implement the program in java This will mean that it will be playable on almost any platform and if I make it as an applet can also be played from the web The fact that java is fully object oriented means that the
18. or if there is a possible way to draw them in order to produce the correct result Another method for removing hidden surfaces is the Z Buffer method What this means is that when you are drawing the image an extra value is stored for each pixel drawn when a pixel would be drawn over a pixel that has been drawn already the depths of these pixels are compared The new pixel will only be successfully drawn if the depth is less than that of the old pixel This solves the overlapping problem with Painter s algorithm by not being concerned with the polygon as a whole however the Z Buffer is far more complex to implement and is on the whole more time consuming Whichever method used back facing polygons can be removed from the scene altogether The most popular and easy way to remove back facing polygons is to store the vertices of the polygons in clockwise order then checking the order of the vertices as they would appear on screen If the vertices are anti clockwise on the screen then the polygon must be facing away from the viewpoint and can be removed from the scene 37 Aspects of Realism Golf Simulation Matthew Winchester 8 3 3 Shading Texturing A large part of building a 3D engine is the implementation of shading and texturing However I have discussed various methods previously in this report so rather than repeat myself please refer to Chapter 5 Research Map Texture on page 22 38 Aspects of Realism Golf Si
19. select a club that will loft the ball high in the air to escape the grass as soon as possible The surrounding landscape must also be considered when selecting a club The distance to the hole may be fairly long but you may have a steep face directly in the way that you will have to avoid In this case you will probably select a much higher valued iron or a putter and take the risk of under hitting the shot You must remember however that you are only allowed to take 14 clubs with you on any game This means that you will not be able to take the full range of clubs The clubs that you select should be scattered throughout the range of available clubs to ensure that you have a club for almost any situation You should always however carry some kind of wood for teeing off and a putter for putting 34 Aspects of Realism Golf Simulation Matthew Winchester 8 Research 3D Engine In order to model a real world environment the data used to represent and describe this world must be stored in three dimensional space The problem that then arises is that to view this world you must first find a way to translate this 3D based data into 2D data that can be mapped directly onto a 2D image 8 1 Basic Theory The basic theory behind 3D engines is based around using trigonometry to translate three dimensional world coordinates into two dimensional coordinates that correspond directly into pixel values that can be drawn onto the screen or
20. t u v 2s Where u Initial velocity v final velocity a acceleration t time s distance These are extremely useful and can be used to calculate the position and velocity of a particle after any specified length of time They are intended for use in a single direction however the movement of a projectile can be modelled in all three axis independently eg the x y and z coords 6 2 Gravity The true equation for gravity takes into account the mass of 2 bodies and the distance between the centres of each This would be quite complex as I would need information about the size and mass of the earth Fortunately I will not need to use that equation The reason for this is that due to the immense size of the earth the acceleration due to gravity g varies by less than one percent within 30km of the Earths surface De Mestre 1991 For this reason we can disregard the mass of the Earth and the distances and simply use the following equation 25 Aspects of Realism Golf Simulation Matthew Winchester F mg Where F Force acting on the ball in Newtons m Mass of ball in Kg g Acceleration due to gravity 9 8ms If gravity was the only force I would take into consideration I could just ignore the force and just use the fact that the ball will be accelerating at 9 8ms towards the ground However as I will be considering other factors I will need to keep track of the magnitude and direction of all forces so
21. 0 17 1 2 Requirements ra e a a a a a et e a a ata iae esri aaeain 70 VIAL COMA E itaatin 70 IESE a NN E OA KIET isis 71 ESIA BA RAOLA TET S EIN i DAE E E SEE S EEE EEEE 74 LFA KNOWN BUGS a a a a E A ASES 75 17 5 RESULTS FROM TEST PLAN cccccsccsssssssceeccececcccccccccsssssssceseeeececececccscecccceeessessseeeeeeece 75 18 PROBLEMS AND CHANGES cccssssssssssssscccsscssssscssccscssscssssssscssccesecesssssscosccosees 76 TGS CREW Pen ct R esate a aa a ec ATEA EAN Lt AET o 76 1822 USERINTEREACE a 76 183 SCHEDULE doo ta SS 76 18 4 REAL WORLDOBTECT SA ile 771 18 5 BALL FLIGHT ANIMATION rennan ana a A a e e eaaa r aaao EEN 771 186 BAT S AADO a E a io 71 187 THE WORD COUNT A E ENRE ad 78 19 FUTURE WORK voscesssscscsseeceisisvievsccsectecccseseissccssasesscsdcavassossbecedecsebccededsesdecsiadasaseaiesebebecess 79 19 1 FIXING THE LAG PROBLEM nescii irer r diees iniii EECC EEEa Ee Airce ci nre 79 19 2 REAL WORLD OBJECTS drean aa a aa a e a a 79 19 3 MULTIPLE PLAYERS kenean nean a a aaa n a ea a I e E 79 IRORA EN H AIDA S PLAY E A EE aia 79 OSME HO ES a aa we 79 1 9 6 LE VEL 2 BY K KO SAE EAE A AOE EA bh hae ee AEE ES 79 20 REFERENCES wesissssssesesscessacsescedecscsasdecadsdsevesesasccsdussecdacecuascscsadosevess cosscsescecccdsescceecesecesesees 80 APPENDIX A PROJECT PROPOSAL ccsccsssssssssssccssscsssccesscssccsscsssscsssssccssccoescees 81 LL SINTRODUCTION a 81 12 AIMS AND OBJECTIVES 43 ca 83 1 3 EXPECT
22. 3 1 Game Rules timescale For this reason I have decided not to concern myself with the full implementation of the rules of the game and merely to provide the basic structure Code Description Priority Notes 3 1 1 The player may not disturb the position of the ball except for on the initial tee shot where they may place the ball anywhere within the set teeing boundary 1 The player has completed the hole when they have successfully placed the ball within the cup When the ball is struck into water or out of bounds they may replay the shot from the same position or take a drop ball at the nearest legal position to the place where the ball went out of bounds R3 2 Golf Clubs Code Description Priority Notes 3 2 1 The system should offer the user access to at least the following clubs Driver 1 Wood 3 Wood 5 Wood 1 Iron 2 Iron 3 Iron 4 Iron 5 Iron 5 47 Aspects of Realism Golf Simulation Matthew Winchester 6 Iron 7 Iron 8 Iron 9 Iron Pitching Wedge Sand Wedge Putter 3 2 2 The woods should give the ball a smaller angle of elevation than the irons 3 2 3 The woods should give the ball more speed than the irons 32 4 The higher the value of the club the greater the angle of elevation they produce 3 2 5 The putter should only be used when the player is on the green and should
23. Aspects of Realism Golf Simulation Details Computing Individual Project Matthew Winchester 97501464 lt Winchester imtoosexy com gt BSc Hons Software Engineering Academic Year 2000 2001 Acknowledgements Project Supervisor Peter Aughton Word Count 14922 words Contents Ts INTRODU CTION iissscessssissssscccdscsscesedaczesssssesccsccecberesecescsecdsssdscscssccecccesoseseccsscsedsos eese cobscesce 5 2 PROJECT DEFINITION esicssdicscsssiccssccciccescessesecccesutsss casccasecscseessecesosssossussousecasestessseesesscess 7 PAA E DV EN B E A 9 Y OSR TEE E EAEE EE EEEN NN 7 DD NEA AEA B DIA SAA AEE a ls a EEEE o olle ad 7 3 PROJECT PEAN visciisssvsdcssescsiccecssesscceesseesesevseoctesedecocousssacsccassassesscscedesessesechsascctecseeosssesscess 8 IA WORK BREAKDOWN mieca ed eee 8 32 LIME ESTIMATION AAEE EEEE E E T AS 10 30 MIESTONES a a a lo e dad 11 SNA ASA AA O TN 12 4 RESEARCH MAP CONTOUR ccccscssssssssssssccsssccssccesscssscsscssosssssescsssscssscesccosseoes 14 4 1 MATHEMATICAL REPRESENTATION OF CURVES cssssssssssccccccsesecssssssesescecscssssseesesessssesess 14 4 2 FREEFORM POLYGONAL MEGSH sccccccssssseccoccessccccccsssescccceueccccsecessssecceseusssseccessaaaccceecees 15 4 3 STRUCTURED POLYGONAL MESH cssssssescccccceccccccessscccccsasccccsecussseeccceaesesseeceesuaacceeseess 17 5 RESEARCH MAP TEXTURL cccsssssssscosscssscccscssscscssssssssssssscsscsscssssscsscssssscssssssc
24. ED OUTCOMES DELIVERABLES ssssscccccccsssscccecessseccocscsccceccusseseccesaaesssecces 83 Aspects of Realism Golf Simulation Matthew Winchester TAME A ida losecsd a i cadodpestou eens 84 153 PROJECTPEAN is 85 1 6 RESOURCE REQUIREMENTS ccsssccsscccssccesecceeccceeseesssseesssscssseeseeessececeseeseseeeeseteessseees 85 Me AREY WORDS dsd 86 APPENDIX B USER GUIDE icsscccccctccsssssssssscccvesecosscssveccecscscccedenseceoscosssessssncecssbuccccsseeesescusss 87 1 RUNNING THE SIMULATION cccccccccccccessssssceecccccccccccccccssssssseceeececeescceceeccecccecessseteeeeeeecs 87 Z PLAYING THE SIMULATION ee 87 3 FEATURES OF THE SIMULATION 00cccecccccessccccccessscceccscescesececssseccecascesscecessucccceeeeueeecces 89 APPENDIX C SOURCE CODE eviscccsssisssssssscsassesesessdesccecscceccacsccesescossesvasssccsededeabccssccovesesece 90 Aspects of Realism Golf Simulation Matthew Winchester 1 Introduction As the title suggests I am planning to create a simulation of the game of golf To do this I am going to have to model and represent a complete 3d world There are several distinct parts of this project that I have identified These are as follows e Map Contour The logical modelling and representation of a three dimensional contoured terrain The golf course e Map Texture The modelling of different textures of the terrain and how the textures affect the ball Textures include short grass green me
25. Fig 6 6 1 shows the realistic new trajectory is more towards the normal to the surface than a perfectly reflected bounce Normal to surface o T Direction of ball before bounce e Realistic bounce 8 Perfect bounce Figure 6 6 1 Showing the direction of a ball immediately after bouncing The amount that the trajectory is altered depends on the texture of the ground Fig 6 6 2 shows the general effect that different surfaces have There are a lot more factors that come into consideration such as the composition of the surface is it sticky is it powdery etc However I feel that this is far too complex a subject to model in too great a depth so Iam going to stick with the hard soft factor 29 Aspects of Realism Golf Simulation Matthew Winchester Bounce on soft surface Normal to surface Bounce on hard surface y Perfect bounce Direction of DE g ball before bounce pp Figure 6 6 2 Showing the effect that the surface texture has on the direction after bouncing 6 7 Rolling The final area of investigation as far as the travelling of the ball is concerned is the investigation into the factors that affect rolling These factors include slope spin and friction Fig 6 7 1 shows the effect of the ball being on a sloped surface N Normal Reaction mg Force due to gravity D F Figure 6 7 1 Showing the force on a ball down a slope due to gravity As you can see from
26. Mapping This entails the holding of additional information for each polygon This information is basically a height mapping that describes the very small scale differences in height across the surface of the polygon Becker and Max 1993 state Bump mapping is an inexpensive way to achieve a good approximation to a macroscopic surface roughness Notice the word Inexpensive what they mean is that it is a rather simple process when compared to others available See 5 4 Bi directional Reflectance Inexpensive meant in the way of speed and memory consumption as opposed to price However it is still a very time consuming process when compared to simple light shading and texture mapping 5 4 Bi directional Reflectance and Texture Dana et al 1999 state Bump mapping preserves some of the appearance of roughness but knowledge of the surface shape is required and shadows cast from the local surface relief are not rendered Dana s paper on Reflectance and Texture introduces and discusses a new texture representation called the BTF Bi directional Texture Function The roots of this are based firmly in the BRDF Bi directional Reflectance Distribution Function Introduced by Nicodemus 1970 For the BTF they have gone to the extent of building a database of images taken from 60 surfaces observed from over 200 combinations of viewing and illumination angles The reason for this is that a single image for texture mappin
27. The Mathematics of Projectiles in Sport 1991 Frank Maddix Human Computer Interaction 1990 Alan Watt Third Edition 3D Computer Graphics Addison Wesley John De Goes Cutting Edge 3D Game Programming with C Coriolis Group Books 1996 James F Blinn Realism In Computer Graphics Caltech JPL 1979 William E Lorenson Boris Yamrom Golf Green Visualization 1992 Fred W Hawtree The Golf Course planning design construction and maintenance 1983 Friction Microsoft Encarta Online Encyclopedia 2001 http encarta msn com 1997 2001 Microsoft Corporation All rights reserved Kristin J Dana Bram Van Ginneken Shree K Nayar Jan J Koenderink Reflectance and Texture of Real World Surfaces ACM Transactions V18 No 1 1999 80 Aspects of Realism Golf Simulation Matthew Winchester Appendix A Project Proposal 1 1 Introduction Computer simulations of the real world have a very wide array of uses These range from entertainment and training to research and speculative planning Examples of these are as follows e Games With the advances in hardware over the past few years games have progressed greatly in the way of realism It is actually quite rare for games nowadays to be released that are not 3D representations in some way In fact the most popular type of game at the time of this project is the First Person Shoot em up These games make the player feel as if they are actually runni
28. alise that Ihave very little chance of creating a game that looks anywhere near as nice as the commercial golf games This project however offers something that the others don t it is based around reality rather than gameplay There are several major flaws in commercial golf games that are in place to aid in gameplay These are factors such as wind Wind is taken into consideration in most golf games but once you have struck the ball the wind stays constant Also the majority of golf games have mostly flat courses I have personally played on a few courses and on all of them there were holes that were either majority up hill or majority 82 Aspects of Realism Golf Simulation Matthew Winchester downhill My simulation will hopefully fill both of these gaps I will implement wind that changes constantly and I will also ensure that I implement realistic course contours My main reason for taking this project is because one of my major interests is the way in which real world situations can be simulated and broken down into a series of equations This is also where my interest in Physics comes from This project will allow me to investigate design and implement various ways of storing and expressing real world entities and events as objects and operations 1 2 Aims and Objectives The main part of this project is simulating realism I do aim to create a very entertaining and playable game but the emphasis will be firmly on accurately r
29. and faces should vary between 30 and 40 from the horizontal 39 Aspects of Realism Golf Simulation Matthew Winchester 9 3 Teeing Grounds The main points to consider when designing the teeing grounds are e The teeing grounds should be perfectly flat or if it must be sloped it should be sloped slightly uphill e The teeing ground should be generally rectangular and aligned roughly in the direction of the hole e The front edge of the teeing ground should be 300mm above the level of existing ground in front of the tee 40 Aspects of Realism Golf Simulation Matthew Winchester 10 Research User Interface The user interface is a hugely important part of most applications especially games No matter how good the application is behind the scenes users will judge it by its interface A good interface will keep the users happy and hopefully they will come back for more 10 1 Theory Maddix 1991 states that HCI Human Computer Interface can be seen very much as an act of communication the aim being the successful transfer of meaningful information between the user and the system It is very important to keep this communication as simple and effortless as possible For example for the user to tell the system to hit the ball it is far more desirable to simply click the mouse button on a button labelled Hit Ball than for the user to manually type Hit Ball The ordering of communication is also very importan
30. are several ways to run this simulation It can be run as a java application or as a java applet To run it as a java application at a command prompt navigate to the directory containing the class files and type java Golf To run it as a java applet you can either a Open the index html file preferably in Internet Explorer but Netscape Navigator will work too this will open and run the game b Atacommand prompt navigate to the Golf directory and type appletviewer index html c Go to http www madsoftware co uk and play online 2 Playing the simulation The controls are relatively simple The toolbar to the right hand side allows you to customise every aspect of the shot To change club click the next and previous club buttons See fig 2 1 BA club Driver Figure 2 1 The club selection buttons To change the power of the shot you simply adjust the Power scrollbar as shown in fig 22 Figure 2 2 The power selector 87 Aspects of Realism Golf Simulation Matthew Winchester To adjust the spin that you place on your shot you use the two Spin scrollbars shown in fig 2 3 Spin EE SST Left None Right Backspin Kx A el Min Figure 2 3 The spin selector To adjust your aim click on the screen see fig 2 4 If you click to the left of the ball you will look left if you click right you will look right The further away from the ball you click the greater the angle c
31. are that they have already been done And I do not feel that they are actually a part of the project they seem more like stages you go through before you actually start the project itself The reason for not including the report writing is that it is not a stage it is something that happens at every stage and so it is basically inferred The actual hand in date for this report is May 4 The activity sequence suggests that the project will be finished by March 22 Unfortunately I do not believe that the project will finish on time and so the extra gap at the end will be a very useful buffer Even if the project does finish within scheduled time the gap at the end will serve to either polish up parts that I am unhappy with or maybe even give me a bit more spare time to revise for my exams 12 Oct 15 Oct 22 Nov 1 1 Nov 8 1 Research Research Research Research Figure 3 3 1 Project Plan Activity Sequence Map Contour Map Texture Objects 3D engine Nov 15 2 Dec 1 1 Requirements Requirements Elicitation Analysis and validation Research Research Ball travel Golf clubs Oct 15 Design Data Structures Design Design Class diagrams Sequences states Tester App Tester App Tester App Ball flight 2D views 3D view De an Tester App Map display Tester App Bounce amp roll Feb 15 2 Feb 1 2 Game Ball Travel Mar 15 1 Technical Game Game Documentation Solid objects S Test amp F corr
32. ascccsccccauacccesccussseescessaaaceseess 34 8 RESEARCH 3D ENGINE wisisicsccsccccoscicisessdessiscsvendececocecctacsessodssacocessensuecaceuadecenbbcsscsdsscesess 35 1 BASIC THEORY e E EE E E E Aoi iki hieea ads ae eee OE 35 8 2 THE GRAPHICS PIPELINE ssssseccccccssscccccsssescoccccccecceccssseccecsecsssseccecsuaccsseccessscescesaaaees 35 SI MEATOR ISSUES A a EE Cac 36 LACAN DCEO ree iteacate cl a sahe huts ce loo da 36 8 3 2 Hidden Surfaces amp Clipping r AE a E E RES Ea 37 VIA E A EA 0AA EE A T e e ed A 38 9 RESEARCH GOLF COURSE DESIGN eeeeoessosssssossssssossoocossoossssosssssossoesoocosssossssssse 39 e E E E EA E ANARE AA e ds a a la A EA 39 OD BUNKERS EA e hla E el EEEE TE A E les 39 9 3 TEEING GROUNDS ed ET 40 10 RESEARCH USER INTEREACE cccssssssosssossccsssssssovcssssssssssccsseessscssssssccscsscees 41 IOI RA R a 1 O Ea E EEE o esha Las eed deena oe ee ee a eee E 41 10 2 POSSIBLE GUI DESIGN E EEE EEEE E EEE A E 41 11 REQUIREMENTS je ccscissescccisdscccscsatisdeeiseseveteccanscecsedbbcsssdsdegenvesecedadecesosesssauecseeeavesseccssese 43 RLBALE TRAVEL e he edades 43 REF BAILE eL teas ect ose eA iia 43 RI 2 BILIAR ida 44 RLSABOA ROS ree ee ht eke aida 44 R2 GOLF COURSE A Oe oR ete ee ee i eee 45 RELE Map OntOur svn cated nae eto 45 R2 2 Map Textures rac ns ives oe a dd a Ae ida 46 TEE ETNII APINE A e een o Sag o a e Mo o ON lags 47 RIMA RULES co a ae stati ue 47 ROO e ds ad ad 47 RADICA Y e ess
33. ation should include details of classes objects relationships between objects data structures and 5 49 Aspects of Realism Golf Simulation Matthew Winchester interaction between objects 6 0 4 A user guide should be produced which should detail how the user should run and control the game 50 Aspects of Realism Golf Simulation Matthew Winchester 12 Risk As this is a relatively small project with only a single person working on it I decided not to go too in depth with the Risk strategies However the considerations that I have made have been listed below Identified Risk Overrunning the allowed time Aversion Strategy To try to regain a little time I could drop a few of my goals I think the main area which could be left out without too much impact is the real world objects bushes and trees etc I could also change my plan from creating a complete game into just a single hole demo Identified Risk Overrunning the allowed word count Aversion Strategy This is a problem that is difficult to remedy The main thing that can be done is to put the sections of little importance into an Appendix This is because the contents of the appendices are not added to the word count This is still undesirable because it is doubtful that the appendices will be read as an integral part of the report and marks could still be lost Identified Risk Being unable to solve a par
34. ause I was running out of time and decided to lower my aims I have added the ability into the 3D engine for any objects to be incorporated into the world as I have done with the flagpole but have not had the time to create any complex objects such as bushes 18 5 Ball Flight Animation I encountered a very large problem when I first tried to integrate the map display with the ball flight The problem was that I had to find some way to show the flight of the golf ball in 3D I could simply render the flight frame by frame however this would be extremely slow I could simply render the map display once and then just draw the ball on top of the static image however this would fail when the ball would should be obscured by the contour of the map as it would simply be drawn over the top of everything Solution What I decided to do was relatively clever For the entirety of the flight sequence the viewpoint could be the same this means that the map only has to be translated once The polygon tree created from this is kept throughout the sequence When the ball is repeatedly translated and added to the held tree the index is added incrementally What this means is that there will be many nodes in the tree representing the ball but each will have a different index When it comes to drawing the scene you can simply draw ONLY the latest index Doing this means that you miss out on the time consuming map translation phase It also means that I coul
35. c e Implement the Tester Application Use it to create and test the algorithms used in the manipulation of real world objects e Implement and test the game itself e Create technical documentation to explain the code for future maintenance e Create a user manual Aspects of Realism Golf Simulation Matthew Winchester 3 Project Plan 3 1 Work Breakdown Create Game Fee Se oe i a ene A al f Trt i Tester Technical User Manual ee ee SEE AE y A o Figure 3 1 1 The initial work breakdown structure Object 3D Map representation display texture e g a tree travel engine Figure 3 1 2 Further work breakdown of Research Map Contour Requirements Analysis and validation Elicitation Figure 3 1 3 Further work breakdown of Requirements Sequence state Data Structures transition diagrams Class diagrams Figure 3 1 4 Further breakdown of Design Aspects of Realism Golf Simulation Matthew Winchester Develop and Develop and test Develop and test test ball flight Map display Ball bounce and algorithm algorithm roll algorithm Implement 2D views Implement 3D view Figure 3 1 5 Further work breakdown of the Tester App Implement Implement Implement Implement Implement Implement Test 3D engine map view ball travel different solid game rules and golf clubs objects correct Figure 3 1 6 Further work breakdown of the Game Figures 3 1 1 to 3 1
36. ce that 3 will cause the ball to decelerate 1 1 8 Air resistance will cause the spin on the ball 4 to decelerate 1 1 9 Wind will cause a force on the ball with 4 direction and magnitude being calculated from the direction and velocity of the wind relative to the direction and velocity of the 43 Aspects of Realism Golf Simulation Matthew Winchester ball Not relative to a stationary point 1 1 10 Wind will affect the magnitude and direction of the forces caused by spin on the ball See 1 1 2 to 1 1 5 R1 2 Ball Impact with Ground Code Description Priority Notes 1 2 1 When the ball contacts the ground the ground absorbs some of the energy of the ball The amount of energy absorbed depends on the angle of impact the velocity of the ball and most importantly the texture of the ground 5 Without this the ball will just bounce forever 1 2 2 If the ball has sufficient energy after the initial impact it will bounce otherwise it will begin to roll 1 2 3 The spin on the ball will cause a force on the ball as in the following table Top Back Right Left Top amp Right Top amp Left Back amp Right Back amp Left Forward Backward Very Slight Right Very Slight Left Forward amp Right Forward amp Left Backward amp Right Backward amp Left 1 2 4 The angle of the bounce will depend on the a
37. completed M3 Application design completed M4 Main algorithms developed Tester app has been used to create all useful algorithms M5 Game is playable M6 Project completed These milestones show a good overview of the main stages that the project will go through The ordering of milestones here does give a good representation of which order they will be completed in the only possible exception would be that M3 and M4 could be transposed This ordering is not sufficient enough to complete the project plan though so a more in depth activity sequence is required 11 Aspects of Realism Golf Simulation Matthew Winchester 3 4 Activity Sequence The sequencing of activities is a very important part of the project plan It gives a clear network of paths that should be followed It enables me to ensure that all work needed before a new activity can begin has already been completed It also helps me to know what tasks can be done concurrently This is very important as having more than one thing that you can work on is more efficient This is because if I got stuck on something I always have something else I can work on and come back to the problem fresh at a later time Figure 3 4 1 shows the activity sequence for this project There are a few things that are not included in this sequence These things are the proposal the project plan itself and the report write up The reason for not including the proposal and the plan
38. d so I have decided to investigate the ways in which spin affects the ball in flight Fig 6 5 1 shows a typical situation with a ball travelling through the air with an anti clockwise spin The main thing to notice here is that on the left the spin of the ball is making the 27 Aspects of Realism Golf Simulation Matthew Winchester surface of the ball move in the same direction as the air whereas on the right the surface of the ball is moving in the opposite direction to the air Direction of travel through air Flow of air Ball spinning against flow of air Ball spinning _ with flow of air Figure 6 5 1 Typical situation of ball flying through air with anti clockwise spin The movement of the surface of the ball against the air causes the speed of the air to change On the right hand side the surface of the ball moving against the air causes the air to rapidly decelerate whereas on the left the air will be decelerated less or possibly even accelerated It is a widely known fact the slower the air is moving the greater the pressure it exerts this means that the pressure exerted by the air on the right is greater than that exerted on the left Fig 6 5 2 demonstrates this fact This difference in pressure causes a resultant force in the direction from the high pressure to the low pressure This means that the resultant force from spin is perpendicular to the direction of travel through the air as demonstrated in f
39. d easily add in an instant replay function that shows the trace of the flight i e draw all of the instances of the ball in the tree 18 6 Ball Shadow Another problem that I came across when implementing the ball s interaction with the map was that it was not always obvious whether the ball was rolling or flying To solve this 77 Aspects of Realism Golf Simulation Matthew Winchester problem I gave the Ball a shadow this shadow is unrealistic in the way that it is directly below the ball rather than angled but it gives a very good representation of where the ball is 18 7 The Word Count This report has a maximum word count of 15000 I have had problems in keeping under this limit and have had to make a few compromises in order to comply with the limit In my Risk strategy I suggested moving some chapters into the Appendices as they don t count in the overall word count however I could not see any sections that I would have voluntarily placed in an Appendix I consulted my project supervisor on this matter and he informed me that the initial project proposal didn t actually have to be part of the report so I put that into Appendix A and wrote a far smaller introduction to give myself a bit more space 78 Aspects of Realism Golf Simulation Matthew Winchester 19 Future Work There are a lot of things that could be improved about this application Possible future work is outlined below 19 1 Fixing the lag pr
40. d to travel if it is hit at full power with the currently selected club 4 2 6 The user must be able to change the direction in which the ball will be struck They must also be able to change their mind and select another direction 4 2 1 The user must be able to select the power with which they will hit the ball This may be an inaccurate process 4 2 8 The user must be able to select how they will hit the ball effectively what spin they will put on the ball This may be an inaccurate process 4 2 9 The user should be able to view the layout of the current hole possibly from an overhead view with a You are here marker 4 2 10 The interface should restrict the types of shot that the user can take to reasonably physically possible shots For example the user should not be able to drive the ball 600 yards R5 Objects Code Description Priority Notes 5 0 1 The golf course should include various real world objects that may include bushes trees fences and signposts 2 5 0 2 The ball should interact with these real world objects in a realistic way R6 Documentation Code Description Priority Notes 6 0 1 All source code produced should be fully commented 5 6 0 2 This requirements document should be kept up to date from creation to completion 5 6 0 3 The design document
41. dium grass fairway long grass rough sand and water e Real World Objects The modelling and representation of objects such as trees and bushes I will have to model the effect they have on the ball when the ball hits them as well as finding an efficient and realistic way to display them e Ball Travel The modelling of the ball This covers the flight of the ball the effect of impact on the ball and the rolling of the ball Factors to be taken into account include gravity air wind effects of spin etc e Clubs The modelling of different types of golf club the different effects they can have on the ball in terms of spin power and direction e 3D Engine The three dimensional display engine Various aspects need to be implemented such as translation of 3d world points into 2d screen points drawing of filled 3d polygons and rendering scenes displaying closer objects over distant object etc e Game Engine The implementation of game rules Enabling multiple players to compete against each other Time permitting possibly include computer opponents of variable skill levels and maybe even network or internet play There are also some separate small projects that I plan to design and build as follows Aspects of Realism Golf Simulation Matthew Winchester e Ball Flight Tester Compromises of 3 simple 2d representations top front and side used to help develop and test the algorithms that I will develop to model the flight
42. e bringing together of the two previous sections The map display and the ball flight This is the only part of the report where figures may be placed and not commented on This is because the diagrams are themselves the design and should be as explanatory as possible Comments are included where further explanation is required 15 1 Class and Object diagrams GolfEngine Ball numFlightAtfectors int xPos double GolfApplet numPollAffectors int yPos double GolfPanel xAngle double zPos double init sed yAngle double xVel double sim GolfPanel ZATE lt eleve y Vel double gt addToolbaro SpnumClubs int zVel double Gui SIM tai currClub int top_backSpin double T panty left_rightSpin double Golf AhePanel GolfEngine stopped boolean main reset inFlight boolean Boa Naa o Pis Dist a a gelbal astDist double GolfCanvas oan pengine pstate int Cue theBall YBall i setWind setVelocity ppictureGenerated boolean E grenslateMap SsetSpin 0 2a ranslateBall hitBall A de _ theEngine crawScene x update nitBall vw drawTitle getCurrentClub 2 g drawScreen getNextClub speed crawScreenUpdate f getPrevClub hasStopped aftcra
43. e the normal to the plane of the polygon Use the Dot Product formula to calculate the angle between this normal vector and a specified light source vector Use this angle to define a ratio or a percentage if you like of the amount of green that the assigned colour will have What is instantly noticeable is that the curves are very jagged and the difference between the colour of the polygons is very distinct and noticeable Fig 13 2 4 shows version 0 3 this version is actually exactly the same as the previous version except that it looks extremely smooth All that I have done is to increase the amount of polygons and reduce the size In fact there are exactly 19602 polygons being drawn This screenshot demonstrates my light shading algorithm very well In fact when I first saw the results in this version I was shocked myself Figure 13 2 3 Screenshot of Map Representation v0 2 54 Aspects of Realism Golf Simulation Matthew Winchester Figure 13 2 4 Screenshot of Map Representation v0 3 Fig 13 2 5 shows version 0 4 There are significant changes between this one and the last The main effect of these changes is that the viewpoint angle is now changeable The user is able to look left right up and down as well as being able to move forwards back and side to side There were several steps needed to accomplish this The major ones were Implement a Matrix class Implement matrix utility functions such as multiplyMatrix Matr
44. eNode 1 y 6 N right right PolygonTreeNode PolygonTreeNode 3 7 left right PolygonTreeNode PolygonTreeNode 2 4 This is a possible object diagram for a case where there are 7 polygons in the scene Traversing this tree will order the nodes as shown by the numbers in the square brackets Or in the opposite direction depending on the traversal method Figure 15 1 5 Object diagram showing a possible structure for the polygon tree 63 Aspects of Realism Golf Simulation Matthew Winchester 15 2 State Charts App Launched Show title 1 Title Screen gt Showing User clicked to start Start sim at the tee User changed shot selection 2 Waiting for User clicked user to take shot iew User clicked Restart o J Overhead view 5 Displaying please wait notice User takes shot f Ball putted TEO 4 Simulation Display 3 Ball Notice displayed is over congratulation Travelling screen 9 6 Displaying overhead view time consuming process User Closes Application ae Figure 15 2 1 State chart showing the transitions between the main states of the system 64 Aspects of Realism Golf Simulation A Matthew Winchester 15 3 Sequence Diagrams This sequence diagram shows the player customising the setup for their shot A
45. ect User Manual Golf clubs 4 Research Map Contour 4 1 Mathematical representation of curves Any curve can be represented using mathematical formulae This has some very distinct advantages the main being the accuracy A curve represented by a formula is perfectly smooth and accurate and allows any point on a surface to be calculated to any degree of accuracy required Curves represented in this way will never look blocky The most common example of mathematical curves is a True Type Font Figure 4 1 1 shows the difference between a True Type Font and a fixed pixel font GOLF GOLF Figure 4 1 1 Showing the difference between 2 enlarged fonts A is System a fixed pixel Font B is Arial a True Type Font As you can see the True Type Font still looks very smooth even when enlarged The fixed pixel type font represents straight lines just as well as the True Type Font The L and F look perfect but the curves the G and the O are excessively blocky and inaccurate In an ideal world the mathematical representation of the terrain would be perfect However the complexity involved in creating the terrain this way is far too much of an overhead Not only is it incredibly difficult to create a terrain this way but it is far too complex to handle the display from a 3D mathematical model to a 2D screen The overhead in time not just in the creation but also in the translation to screen
46. ees 20 SA TIGHT SHADING A E EE fae a dese ee ee eee e S 20 5 2 TEXTURE MAPPING E e e e a eae cae O NAO 21 SO BUMP MAPPING A ssa ck eet bags E EE A AES 21 5 4 BI DIRECTIONAL REFLECTANCE AND TEXTURE ccsssscccccccesssecccceseessccccecessesceeseasesceees 22 5 5 SURFACE INTERACTION sssscccccccsssseccoccecccccccccssssccccceecccesecssssseccceccessecccessaaeseseeeenseecees 23 SO DECISIONS 3isc5 Sete ete ca ete ele ta ica a ne beaded ET 24 6 RESEARCH BALL TRAVEL icccssssssssscccscecs csssssssossseccssccesdscesvescdscecsoacsseodasssasesccesessasessse 25 6 EQUATIONS OF MOTION 0 A AA ana 25 2 NI E EEE 25 6 3 ATR AND WIND PEIER AEE Cee Hd eS 26 Aspects of Realism Golf Simulation Matthew Winchester 6 4 DENSITY TEMPERATURE PRESSURE amp HUMIDITY cccccseesscccccccceeceecccesceeesseesssseeeenes 27 6 5 EFFECTS OF SPIN IN FLIGHT ccsscsecccccccsscccccccssseccccescscccesceessseccceccusseeccessauaccssceeenseess 27 6 6 CONTACT WITH GROUND cccccecccsssscccccccsccssccccsssesccscsccccssccccssseceesccssssscscessccssesecssessececs 29 ARONA ones eae O a ed ea ees 30 7 RESEARCH GOLF CLUBS iissciciscccccsssccccsasectcccsiccveseccecsecdcedssssscssseccedevevcoadsesoscessesssesssues 32 TASTY RES OF CLUB elias eeure castorate etd ie ctor tote Ria eat ol 32 LA Midi 32 LEADER eb RE i 32 TEV SX RULO e AL aa Db bis 33 2 EFFECT ON BALL A ae 33 7 3 WHEN TO USE WHICH CLUB sssssecccccccssscccccccsscccccccsssseccecse
47. epresenting the physics behind the game of golf rather than literal rules of the game A large part of this project will be to implement a 3D engine I will need to do this so that I can display the 3D representation of the world on a 2D screen This 3D engine will have to be able to translate points from a 3D world to 2D screen points from any viewpoint and angle It will also have to be able to render a realistic image of the landscape the golf course so that the player can picture the situation they are in Overall the main aim of this project is to create a piece of software that simulates the game of golf so well that someone who plays golf regularly would say That is actually what would happen 1 3 Expected Outcomes Deliverables At the end of this project I plan to have produced the following not necessarily in order e Project documentation e Requirements Specification e Design Document e Source Code e Project write up 83 Aspects of Realism Golf Simulation Matthew Winchester e Application e Java classes runnable as standard application or web applet e Additional Documentation e User guide explaining how to play the game 1 4 Methods Throughout this project I plan to make use of UML UML provides many different ways to represent and model the various parts of the system Use case diagrams for example provide very useful information and help in the elicitation of requirements and also in the building
48. equence diagram The calculation of physics behind the ball flight NB The sequence of calculating the rolling of the ball is almost exactly the the same as the flight but with the RollAffectors Slope Friction and RollingSwerve instead of the FlightAffectors Gravity Drag and Swerve Aspects of Realism Golf Simulation Matthew Winchester This sequence diagram shows the process of turning the world coordinates of multiple objects into a sorted gt tree of polygons that have been translated into screen coordinates World to View coords Translat View to Screen coords translate ball translate shadow theEngine tranMatrix rootNode theMap Map theFlag Flag theBall Ball GolfEngine Matrix PolygonTreeNode Create Matrix to move and rotate points depending on view positi and angle translate tranMatrix rootNode For each point Translate World to View coords Le Translate View to Screen coords o For each triangle addNode I lt ____ Create a node rootNode i translate tranMatrix i gt For each point Translat gt For each triangle addNpde lt Create a node rootNode i translate tranMatrix rootNode gt addNode IA addNode lt tNod lt rootNode l
49. ester Facet Face Gouraud Phong Figure 5 1 2 A comparison between Facet Face Gouraud and Phong shading Picture is from the New York Institute of Technology Computer Graphics Lab 5 2 Texture Mapping Texture mapping is where an image is overlaid onto a 3D object often simply a single polygon As I mentioned previously 4 2 Freeform Polygonal Mesh it is a way to make very roughly modelled shapes look far more detailed See fig 4 2 2 The process behind texture mapping involves loading a 2D bit mapped image into memory associating the x y coordinates of the polygon to the x y coordinates often referred to as u v coordinates but they mean the same thing of the relevant part of the bitmapped image Each pixel of the polygon is then mapped onto a pixel in the stored image and the colour of the stored image is then used as the colour of the polygon This description is merely an overview of an incredibly complicated process and is by no means complete 5 3 Bump Mapping in 2 D texture mapping when a single digital image of a rough surface is mapped onto a 3 D object the appearance of roughness is lost or distorted Dana et Al 1999 This is because a non smooth surface looks very different when viewed from different angles Even slight bumps in the surface could cover part of the surface when viewed from an acute 21 Aspects of Realism Golf Simulation Matthew Winchester angle One solution to this problem is Bump
50. g is insufficient In the real world viewing a texture from an angle causes much of the texture to be obscured by the peaks in the texture also shadows are cast from these peaks and the effect of these shadows depends on the lighting conditions Single image texture mapped objects just show a distorted version of how the texture looks head on Any engine built to use the BTF or BRDF is guaranteed to be painfully slow Far too slow in fact to even consider using them for my golf simulation However their use is in applications that require incredibly accurate images to be produced regardless of time taken 22 Aspects of Realism Golf Simulation Matthew Winchester 5 5 Surface Interaction It is not just the displaying of the various surfaces that I must be concerned about In fact more importantly in this project is the realistic modelling of the interactions with the surfaces I could talk about general properties of surfaces such as hard surfaces causing the ball to bounce higher than softer surfaces However surfaces such as long grass are more complex than that the ground underneath may be hard but the grass itself may trap the ball I have identified the following distinct types of surface and have described the properties of each Green This is very short grass The surface has very few major deviations and so is generally very smooth This tends to be a very hard surface and causes the ball to bounce relatively high I
51. gger as well The change in control method means that the user can now explore the map use the mouse to look where they like and the arrow keys to move in the direction they are looking Figure 13 2 6 Screenshot of Map Representation v0 6 56 Aspects of Realism Golf Simulation Matthew Winchester The final version of this tester application that I developed is version 0 7 Fig 13 2 7 shows a screenshot taken from it There are 2 obvious major advances in this version The first is the introduction of different textures to the map Shown here is Fairway Green and Sand The texture is allocated to different polygons mathematically meaning that any polygons within a certain area get assigned a set texture The main advantage of this is that I could easily raise the frequency of the polygons to produce a really smooth looking map without any of the obviously jagged edges The second main advance in functionality is the introduction of multiple objects OK the objects I created aren t exactly very useful for the Golf Simulation but they do demonstrate the power of the engine If I do end up creating real world objects such as bushes and trees they will be relatively easy to add into the 3D engine 9 16 Figure 13 2 7 Screenshot of Map Representation v0 7 All of the versions of this application have been written as java applets and are available for all to see at http www madsoftware co uk please take a look 57
52. h getBounce getAngie getDeviation posVal drawP olygon a flagPol points Y as vl Matrix Vertex3D ee rows int isTriangle boolean cols int edasi su ertex3D bis Translated boolean Bvalues double 7 Vertex3D newPoint3D Point3D E M Vertex3D x double y double z E ero paa o Color stranCo me es Panel3D setValue oer a vertB a addValue Gi original aaa ranslate representPoint ome translated translateVertex oP oint ScanPolygon Point3D translateOriginal rows exists boolean x double _ translateOriginalVertex cols minScan int y double E calculateColor maxScan int 2 double yetDistance eleft int Ee getMinDistance right int Point3D normal getMaxDistance scanProcessed boolean Point3D drawable resize isOnScreen ScanPolygon copy draw setup equals debug processLine length orocessPoint minus Figure 15 1 2 Class diagram showing the classes concerned with the 3D engine NB The Object3D class is an abstract class This means that it can be extended references to it can be held but it can not be instantiated 61 Aspects of Realism Golf Simulation Matthew Winchester
53. hanges So to make minor alterations to your aim click very close to the ball l Figure 2 4 The shot screen click on it to change your aim At the bottom right of fig 2 4 is the wind indicator The direction of the line shows the direction of the wind up means forward etc while the length of the line shows the strength of the wind The wind will continue to change throughout the flight of the ball To take your shot click on the Take shot button To restart from the teeing position click on the Restart button To view the layout of the course and see where you are on it click the Overhead View button All these buttons are shown in fig 2 5 88 Aspects of Realism Golf Simulation Matthew Winchester Take Shot Overhead View Figure 2 5 The control buttons 3 Features of the simulation This simulation takes into account factors such as wind and spin and also factors such as deviations due to the texture of the ground This means that when you are in the sand hitting the ball with a driver may produce a very unexpected result The green has been designed to be very difficult to putt on This is deliberate to make sure that the accurate modelling of the rolling of the ball is seen by the player 89 Aspects of Realism Golf Simulation Matthew Winchester Appendix C Source Code The source code has been printed in alphabetical order of class names with a header on each page to show wh
54. he requirements have been split into various sections to enable easy reading I decided to express the requirements in plain text rather than through some kind of formal specification language as the majority of them are observational also the data structures are extremely complex and would be best created in the design phase The titles for the different sections here do not adhere to the standard expressed throughout the rest of this document For example the first section would have been 11 1 but is actually named R1 1 This is because the requirements should have their own coding system to enable easy referencing R1 Ball Travel R1 1 Ball Flight Code Description Priority Notes 1 1 1 The flight of the ball must logically and 4 visibly be affected by gravity air resistance wind and spin 1 1 2 If the ball has topspin it will cause a 4 downward force that will cause the ball to dip 1 1 3 If the ball has backspin it will cause a lift 4 force that will cause the ball to float further 1 1 4 If the ball has right spin it will cause the ball 5 Right spin is as to curve to its left if the ball was struck on its right side 1 1 5 If the ball has left spin it will cause the ball to 5 Left spin is as curve to its right if the ball was struck on its left side 1 1 6 While the ball is in the air gravity will exerta 5 force in a downward direction 1 1 7 Air resistance will result in a drag for
55. ich class it is This is java source code It is available from me on request if you are interested email me at winchester imtoosexy com 90
56. ig 65 3 Fast air Slow air Low pressure High pressure a gt gt Ball spin causes air Ball spin either accelerates or slightly decelerates the flow of air to greatly decelerate Figure 6 5 2 Showing the differing air speeds and hence pressure of a spinning ball Resultant force due to pressure difference Figure 6 5 3 Showing the resultant force due to spin on a ball in flight 28 Aspects of Realism Golf Simulation Matthew Winchester A sphere will spin on any axis that passes through its centre This could be modelled by storing the horizontal and vertical angles of the axis along with its angular velocity However this data is very difficult to work with Instead as I will be modelling the flight of the ball horizontally separate from vertically the spin of the ball can be successfully modelled as 2 different values These are its horizontal left right spin and it s vertical top back spin 6 6 Contact with ground To effectively simulate the bouncing of the golf ball I have had to investigate the physics behind bouncing Fig 6 6 1 shows what happens when a ball strikes the surface If the ball and surface were perfectly flat hard and frictionless the ball would bounce off the surface with the angle of reflection equal to the angle of incidence This is far from realistic though when the ball strikes the surface the surface absorbs a lot of the ball s energy and also alters the ball s trajectory As
57. is a single golf ball which is probably going to be modelled as a single point What this means is that with the map structured in this way you can work out exactly what polygon is directly beneath or above the ball simply by knowing the coordinates of the ball on the horizontal plain This means that to detect when the ball has hit the ground you only have to check a single polygon This will make the game much faster and a lot more feasible to write in Java 18 Aspects of Realism Golf Simulation Matthew Winchester I had 2 different ideas for what the structure could be Figure 4 3 3 demonstrates the 2 different structures Structure a seems to be a lot more adaptable to different type of curves than b but would be a lot more difficult to store and manipulate the map data Structure b is a far simpler structure but could cause more unnatural looking results than a b Figure 4 3 3 Two possible mesh structures The large dots indicate the stored vertices 19 Aspects of Realism Golf Simulation Matthew Winchester 5 Research Map Texture This part of my research actually covers 2 topics 1 The display of the map texture 2 The interaction between the ball and the different surfaces 5 1 Light Shading Light shading is needed to show the shape and contour of an object that has a solid colour Fig 5 1 1 shows 2 cubes a is light shaded while b is not As you can see light shading varies the colour of an object
58. ix Matrix Create matrices to take care of the rotating of the points Multiply each point by the translation Matrix The issue now is that what has always been the back of the picture can now be the front of the picture This issue has serious implications Mainly that the foreground may get overwritten by the background To solve this I took the following steps Implement a binary tree to hold references to three points i e a node will represent a triangle Add all visible triangles to this tree with the tree sorting by the distances of the triangle from the viewpoint To draw the map traverse the tree drawing each triangle in turn starting with the furthest away 55 Aspects of Realism Golf Simulation Matthew Winchester Figure 13 2 5 Screenshot of Map Representation v0 4 Fig 13 2 6 shows a screen shot taken from version 0 5 or 0 6 These 2 versions look the same the only difference really is the control method The main advance over version 0 4 is the eradication of bugs Version 0 4 was painfully slow I initially thought it was because of the introduction of matrixes for changing the viewing angle and for the tree to sort every polygon However I was not fully convinced and set out to try to speed it up I discovered that I had overlooked something I was never clearing out the polygon tree and so I was just permanently adding nodes Once I stopped this the speed was drastically improved so I made the map slightly bi
59. ld not be a major problem as the engine is built to display objects the flag for example however realistic interaction would have been quite a task With extra time I would have liked to implement this 17 4 Known Bugs There are no bugs as such There is one flaw with the program that I haven t had time to eradicate This flaw is that occasionally the 3D engine will encounter a scene that takes far too long to generate This results in the changing of direction to pause or the flight of the ball to be extremely jerky The reason for this is that I have not implemented full polygon clipping What this means is that if a polygon is at all on the screen I draw it When the polygon has been translated it may be just on the screen and a large part of it is off the screen It is this off screen drawing that is causing the major lags To solve it all I have to do is to clip the polygons to the edges of the screen however I have not had time to do this and seeing as it is not a major bug and does not crash the application I am willing to hand it in as it is 17 5 Results From Test Plan Every test from the test plan was successful The application looks and feels very natural and realistic The user interface makes possible any shot you wish to take The application never crashes but occasionally pauses see known bugs above 75 Aspects of Realism Golf Simulation Matthew Winchester 18 Problems and Changes In this section I ide
60. long grass rough sand and water 3 Objects The modelling and representation of objects such as trees and bushes I will have to model the effect they have on the ball when the ball hits them as well as finding an efficient and realistic way to display them 4 Ball Travel The modelling of the ball This covers the flight of the ball the effect of impact on the ball and the rolling of the ball Factors to be taken into account include gravity air wind effects of spin etc 5 Clubs The modelling of different types of golf club the different effects they can have on the ball in terms of spin power and direction 6 3D Engine The three dimensional display engine Various aspects need to be implemented such as translation of 3d world points into 2d screen points drawing of filled 3d polygons and rendering scenes displaying closer objects over distant object etc 7 Game Engine The implementation of game rules Enabling multiple players to compete against each other Time permitting possibly include computer opponents of variable skill levels and maybe even network or internet play There is also a separate small project see Methods below and Figure 1 that I plan to design and build as follows 8 3D Tester Compromises of 3 simple 2d representations top front and side along with a simple point line 3d representation I realise of course that there are many golf simulations in existence already I also re
61. mulation Matthew Winchester 9 Research Golf Course Design Although it is not an important aspect with regards the physical realism of this golf simulation I felt that I should investigate into the area of golf course design One of my main reasons for this is that a lot of users will not see the complexity of the implementation of the physics all they will see is a game and with a badly constructed golf course probably a pretty poor game 9 1 Greens I found various pointers as to how to construct the putting greens These are as follows e The green should be an irregular shape e The green should be of sufficient size that a reasonably accurate ball struck from a fair distance away has a good chance of stopping on it The average recommended size for a green is 500m e The green should be contoured in such a way as to be free from moisture collecting hollows puddles e The slope at any part of the green should be no more than 1 in 8 I also discovered some guidelines to help in the building of the area surrounding the green These are as follows e The area should include informal banks in a variety of shapes mounds and hollows e These banks should have a slope of no greater than 1 in 4 9 2 Bunkers There are a few general guidelines for the creation of Bunkers Sand Traps These are as follows e Bunkers should all vary widely in area plan and elevation e The average size of a bunker should be about 75m e S
62. nent double Ball 2 Component double o Force x double y double z double setSpin Force oe N addForce newForce Force void y 2 speed hasStopped Swerve atfect Figure 14 1 1 The data structures for the implementation of the Ball Flight algorithms 58 Aspects of Realism Golf Simulation Matthew Winchester 14 2 The Application Fig 14 2 1 shows a screenshot taken from the tester application As you can see it has been built to enable me to view the results from many different test runs at the same time This has enabled me to compare the various affecting factors in order to find suitable and acceptable value ranges 25 Horiz Velocity Vert Velocity 42 Wind X Coord I Wind 2 Coord 2 Spin Left Right mi zl Spin Top Back 0 me Clear Screen Figure 14 2 1 Screenshot of the Ball Flight Tester application This application was originally going to be built with a 3D view but I decided to build the map view separately so as you can see I placed the control panel in its place The control panel allows you to adjust the initial velocity the wind and the spin imparted on the ball 59 Aspects of Realism Golf Simulation Matthew Winchester 15 Design This section is the system design for the overall simulation It includes th
63. ng around jumping and shooting Of course with games like these the emphasis is on making the software look real rather than being based on ensuring the accurate implementation of the laws of physics e Flight Simulations Flight simulations are used in the training of pilots They are an invaluable tool because they place the trainee in a very realistic simulation of a situation where decisions and actions are critical and even life threatening e Advanced CAD CAM There are several instances of software where simulation is used for planning and designing An example of this is the software used in the construction of Thrust SSC the Super Sonic Car The software was vital in the design of this vehicle to ensure that the airflow over the surfaces at immense speeds would not cause any sort of dangerous incident such as the car lifting or flipping As the title suggests I am planning to create a simulation of the game of golf To do this I am going to have to model and represent a complete 3d world There are several distinct parts of this project that I have identified These are as follows 1 Map Contour The logical modelling and representation of a three dimensional contoured terrain The golf course 81 Aspects of Realism Golf Simulation Matthew Winchester 2 Map Texture The modelling of different textures of the terrain and how the textures affect the ball Textures include short grass green medium grass fairway
64. ngle of impact the angle slope of the ground at the point of impact and the texture of the ground R1 3 Ball Roll Code Description Priority Notes 1 3 1 The rolling of the ball is affected by wind slope angle of ground the texture of the ground and the spin on the ball 4 1 3 2 The wind has a very slight affect on the ball and this affect is calculated relative to the balls direction and velocity See 1 1 9 1 3 3 Spin on the ball causes forces as in the table specified in 1 2 3 1 3 4 Spin on the ball is very quickly deteriorated and becomes topspin spinning enough to move the surface of the ball at the same speed as the ball is rolling Think of it like a wheel rolling across the ground 44 Aspects of Realism Golf Simulation Matthew Winchester 1 3 5 The ground offers resistance to the ball with a force that depends on the normal reaction of the surface on the ball and the texture of the ground 1 3 6 If the ground that the ball is on is sloped gravity will exert a force on the in the direction down the slope with magnitude relative to the gradient of the slope 1 3 7 It should be possible for the ball to momentarily stop and then move again For example if the ball just rolled directly up a steep slope it may momentarily stop and then roll down the hill again R2 Golf Course R2 1 Map Conto
65. ntify the areas of the project where I encountered problems and state how I solved them Also I identify the changes I made to the project since I created the project plan and the initial proposal 18 1 R U P In my project proposal Appendix A I stated that I would be using the RUP Rational Unified Process throughout the lifecycle of this project However I changed my mind The RUP is most useful in the development of multi user and information centred systems it didn t really tie in with this application I also believe that it would have taken far more time and with there being a shortage of time anyway I was very quick to decide against using it 18 2 User Interface My initial plan completely overlooked the development of the user interface So I just went ahead and did some research and Interface creation anyway See Chapter 10 18 3 Scheduling My estimations for the time the various stages of the project were completely wrong I underestimated the impact of coursework from other modules on my time At one point I had been up to 2 months behind my schedule luckily I had been generous with a few of the later tasks and also I had planned to finish by March 22 whereas the project didn t need to be completed until May 4 76 Aspects of Realism Golf Simulation Matthew Winchester 18 4 Real World Objects Real world objects Bushes Trees and Signposts for example have not been implemented in any great depth bec
66. oblem The problem of the application pausing occasionally is the most frustrating part of the application and is the only thing that is stopping me from being completely happy with what I have produced If I were to continue working on this project that would be the first thing that I would do 19 2 Real World Objects The inclusion of real world objects was part of my original plan and was omitted due to lack of time This would be the next major aspect that I would work on 19 3 Multiple players Including the ability for multiple players would make this much more of a complete game It is not necessary for the simulation though as the emphasis is on the physics 19 4 Network play Once multiple players have been implemented I would love to make the game networkable with play over a LAN and hopefully the internet too 19 5 Multiple holes If I were to work on this more to make it into a proper game I would have to build in the ability to have many different golf courses with multiple different holes 19 6 Level editor As the golf course layout is generated mathematically it would be fairly trivial to build a level editor so that players could make and play their own golf courses 79 Aspects of Realism Golf Simulation Matthew Winchester 20 References Vartan Kupelian www golfonline com 2001 Barry G Becker Nelson L Max Smooth Transitions between Bump Rendering Algorithms 1993 Neville De Mestre
67. of the ball e Map Representation This will be built initially as a generic 3D engine but will be used to develop the data structures and algorithms for the development of the contoured golf course For more information about my initial plans for this project please view my project proposal in Appendix A Aspects of Realism Golf Simulation Matthew Winchester 2 Project Definition The Project definition is an overview of the main aims and objectives of this project The overall aim is a description of what the final product will be It does not cover anything to do with how I am going to go about reaching this goal The objectives cover the sequence of goals that I aim to complete during this project This includes the processes I plan to go through not just objectives of the product 2 1 Overall Aim The aim of this project is to create a playable simulation of the game of golf It will simulate the laws of physics as accurately as possible whilst being an enjoyable and playable game 2 2 Objectives e Research the possible ways to model and represent the various separate aspects of the system map contour map texture objects the ball etc e Produce a requirements document to encompass every aspect that the system must implement e Assess the Risks involved in this project and produce a risk document e Design the architecture of the software the class definitions the sequences of events the data structures et
68. of loft 0 degrees of loft would be perpendicular to the ground Vartan Kupelian from golfonline com talks about the rapidly expanding area of Trouble Woods these are Woods numbered 6 7 9 and 11 These clubs are not commonly used but are preferred by some to the longer Irons because they feel they are easier to hit NB Just because they are called wood doesn t mean they are made from wood 7 1 2 Iron The iron clubs have a more angled face than the wood clubs This causes them to give the ball a much higher flight than a wood club would The usual types of irons are 1 Iron down to 9 Iron with the higher the number the more angled the face NB Again they will probably not be made from iron Wedges 32 Aspects of Realism Golf Simulation Matthew Winchester Wedges are again a progression in the amount of angle on the face of the club They are seriously angled and hit a lot higher that they do far They are usually used in areas where the ball is in a particularly bad lie that is that it is surrounded by grass sand etc The usual flavours are simply pitching wedge and sand wedge NB Wow They do actually look like a wedge 7 1 3 Putters These are relatively simple clubs They usually have a completely flat face so that they can hit the ball without it being chipped into the air There are not many types of putter available they all do the same type of thing The only major difference in putters is that some have a
69. on Matthew Winchester 17 2 Screenshots The following images are actual screenshots taken from the finished simulation As this simulation was written so that it could be displayed as a java applet you can play this simulation online at http www madsoftware co uk ES Golf Simulation _ Sa None Right Take Shot Overhead View Figure 17 2 1 Screenshot The teeing ground looking towards the pin 71 Aspects of Realism Golf Simulation Golf Simulation Matthew Winchester Par 4 opin 434 Club Driver Saat None Right Min Take Shot Figure 17 2 2 Screenshot Overhead view Notice the ball on the teeing ground 4 Golf Simulation Figure 17 2 3 Screenshot The ball in flight notice the shadow approaching the fairway Par 4 opin 434 Club Driver aes Ts None Right Min Overhead View 72 Aspects of Realism Golf Simulation Matthew Winchester Golf Simulation 4 Distar pin Club Driver EEE None Right Take Shot Overhead View Figure 17 2 4 Screenshot The ball in a bunker Golf Simulation Club Putter Power 0 70 None Right pin a aT Min Take Shot Overhead View ul Figure 17 2 5 Screenshot The ball on the green 7m from the pin 73 Aspects of Realism Golf Simulation Matthew Winchester es Golf Simulation Congratulations You have successfully putted the ball HT None Right Backspin Kx Min Overhead Vie
70. ould be very inaccurate 225 Fairway should have the following properties a It should offer medium resistance to balls rolling over it b It should absorb a medium amount of energy when the ball impacts on it c It is recommended to display Fairway as a medium green colour d Striking the ball from the Fairway should be relatively accurate 2 2 4 Green should have the following properties a It should offer little resistance to balls rolling over it b It should absorb only a little energy when the ball impacts on it c It is recommended to display Green as a light green colour d Striking the ball from the Green should be very accurate 2 23 Sand should have the following properties a It should offer medium resistance to balls rolling over it b It should absorb almost all of the balls energy on impact so the ball will probably not bounce 46 Aspects of Realism Golf Simulation Matthew Winchester c It is recommended to display Sand as a brownish yellow colour d Striking the ball from the Sand should be fairly accurate 2 2 6 Water should have the following properties a As soon as the ball enters the water it is considered as dead The ball cannot roll across or bounce on water b Water is recommended to be a bluish colour The game of Golf is extremely complex with far too many rules for me to implement in this R3 Game R
71. ponsibility of calculating the velocities is with the GolfClub class Figure 15 3 5 Sequence diagram showing the interraction when the player takes their shot 68 Aspects of Realism Golf Simulation Matthew Winchester 16 Test Plan As this simulation will not be an information system as such the types of test O can successfully perform are very limited I cannot specify a pre planned input and check that the output is equal to a pre calculated output What I can do is to check that various observations occur For these reasons I have kept this test plan to a rather simple list of tests These tests are 1 Does the ball fly realistically Is it affected by gravity wind and spin in the correct way 2 Does the ball bounce realistically When the ball bounces on a sloped surface does it bounce at an appropriate angle When the ball lands on a soft surface does it bounce lower 3 Does the ball roll realistically Is it affected by the slope of the ground the wind and the spin on the ball 4 Does the golf course look relatively realistic Can you judge the contour and texture of the course visually 5 Do the golf clubs react realistically Do the irons loft the ball higher than the woods for example 6 Is the user interface adequate Can the user accomplish any task they wish to without too much trouble 7 Does the application ever crash 8 Does the application ever produce unexpected results 69 A
72. r and RollAffector classes are abstract classes See above for explanation 62 Aspects of Realism Golf Simulation Golf Matthew Winchester Golf and GolfApplet objects will we be created if the simulation is run as a java application GolfApplet will be created if the simulation is run using a web browser or an applet viewer never exist at the same time Golf thePanel E GolfPanel 1 The GolfCanvas is the class N 1 that runs the game it handles the interraction 1 between the GUI and the theCanvas engine lt controls the GolfCanvas program flow and tells the engine when to do what 4 theEngine GolfEngine GolfApplet The GolfPanel is used to create the GUI This includes creating _ the GolfCanvas The Panel does not control this GUI though all of the controlling event handling and altering is handled by the GolfCanvas producing an Image to show the The GolfEngine encompases the 3D engine and the physics parts of the system It is capable of current view of the golf course This Image is used by the GolfCanvas and is incorporated into the User Interface Figure 15 1 4 Object diagram showing instances of the main driving classes rootnode PolygonTreeNode PAS left right PolygonTreeNode PolygonTre
73. spects of Realism Golf Simulation Matthew Winchester 17 Game Implementation 17 1 Coding Standards In an attempt to keep the source code as readable and maintainable as possible I have decided to draw up some simple coding standards These are as follows 17 1 1 Naming Conventions All Classes methods attributes and local variables must be named in such a way as their meaning is obvious I do not believe it is necessary to denote type String int etc and scope Global local etc in the name of variables attributes as this makes their names far more complex and difficult to follow 17 1 2 Requirements Tracing To help with tracing the implementation of the requirements I am going to add comments into the source code wherever the code is directly or indirectly satisfying a requirement The comments will be in the following format REQ 1 3 2 This standard format must be followed so you can search the text for any requirement 17 1 3 Commenting All source files should be commented with a header stating when it was created and what the purpose of the class is Where necessary comment within the source code to help explain the purpose and theory behind the code The closing curly brace of each method should be commented with the name and parameter list of that method For example drawScene Graphics This is to enable easy navigation around the source file 70 Aspects of Realism Golf Simulati
74. t also has very little resistance to rolling When the ball is struck from this surface it will travel away very accurately because there is little to get in the way Fairway This is medium length grass This surface may have some considerable deviations but is on the whole relatively smooth The ball will bounce fairly high off this surface as it is fairly hard and the grass is not too long The ball will also roll well across this surface Striking the ball from the fairway will result in a very accurate shot Rough This is long grass or other very rough course material This surface will absorb a lot of the energy of the ball and will cause either very low bounces or no bouncing whatsoever A ball will not roll very far through the rough because of the length and density of the grass The grass enveloping the ball will also cause any strokes taken from the rough to be extremely inaccurate Sand Literally meaning sand as found in bunkers sand traps When the ball lands in sand almost all of the energy should be absorbed so the ball will either not bounce or will bounce very low Sand will not offer as much resistance to rolling as rough will but the ball will definitely not roll very far across sand Strokes taken from sand will be relatively accurate but will have to be very lofted to help the ball escape from the sand otherwise it won t really go anywhere 23 Aspects of Realism Golf Simulation Matthe
75. t it should be as natural as possible For example Good Order Bad Order Display overhead view of course Select shot spin Select club Select shot power Select shot direction Hit Ball Select shot power Select shot direction Select shot spin Select club Hit Ball Display overhead view of course 10 2 Possible GUI design I have created a design for the user interface that is relatively simplistic yet effective Figures 10 2 1 and 10 2 2 overleaf show this interface As you can see the input makes use of scroll bars to select the required values Whilst this is unusual for a golf game it is actually a very standard way of selecting a value from a range and would be very effective for this situation The direction indicator is altered simply by clicking anywhere on the screen 41 Aspects of Realism Golf Simulation Matthew Winchester Wind Indicator 3D Display Direction Indicator Figure 10 2 1 Possible design for the user interface Hole 1 Par 4 Stroke 1 Distance from pin 340m These values will change depending on the club that is selected This will have no effect when the putter is selected M Take Shot Overhead View Restart Game Figure 10 2 2 A possible tool bar for the user interface 42 Aspects of Realism Golf Simulation Matthew Winchester 11 Requirements This chapter defines the requirements for the development of the Golf Simulation software T
76. t response for real time applications such as a training flight simulator it is very doubtful that you would implement texture mapping on grass and trees etc However if you were building an engine that has to create high quality images regardless of time taken such as 3D modelling packages you would probably implement every effect you could think of A possible compromise is to use different rendering algorithms depending on the distance of the object Becker and Max 1993 36 Aspects of Realism Golf Simulation Matthew Winchester discuss the implementation of this and state the main reasons for this being that a lot of time is being wasted calculating detail that is too small to be displayed 8 3 2 Hidden Surfaces amp Clipping Hidden surface removal is a very important part of any 3D engine It is very important that objects in the foreground are not hidden by objects behind them To prevent that from happening there are a number of different methods that can be employed The most simple is Painter s algorithm Painter s Algorithm involves sorting all of the polygons in a scene and drawing them in order starting with the furthest away What this accomplishes is that the objects in the foreground are drawn on top of the objects in the background That on it s own is not quite enough There will be instances where the depth of polygons will overlap in this circumstance it is not obvious which polygon to draw on top
77. that I may discover the resultant force from all affecting factors 6 3 Air and Wind When a projectile travels through any fluid gas or liquid resistance will cause the projectile to decelerate and eventually stop This Drag force is directed in the opposite direction to the direction of travel of the projectile In practice the magnitude of this force is not directly proportional to the speed of the projectile however De Mestre 1991 states that at low speeds through low density fluids such as air the drag can be assumed to be directly proportional to the speed without significant loss of accuracy This means that the calculation for the drag force is much simpler than it could have been The following formula can be used F mkv Where Drag force in Newtons mass of projectile in Kg velocity of the projectile in ms resistance coefficient per unit mass unti st 1 Pr This equation is over simplified for general use because it doesn t take into account the shape and texture of the projectile It is fine for use in this project because the ball is assumed to be perfectly symmetrical and I am not going to be modelling this for any other objects Wind is very easy to model all that the wind does is to change the speed of the ball relative to the air What this means is that to account for the effect of the wind all that has to be done is to discover the speed relative to
78. the points rather than polygons is to prevent repetition of data This would be because a single point can be used by up to 6 different polygons Storing them only once means that they can all be translated from world coordinates to view coordinates and then to screen coordinates in one simple pass The formula to calculate the array element representing a specified point is as follows currentPoint COLS 3 i where COLS is the number of columns of points that exist in the map j the row that the point is on 1 the column that the point is on Figure 13 1 1 The chosen structure of the map 13 2 Map Display 52 Aspects of Realism Golf Simulation Matthew Winchester Fig 13 2 1 shows version 0 1a of my map representation program It is a wire frame representation of a randomly generated map This program can be interacted with moving the mouse over the applet will move the viewpoint up down left or right right clicking moves forward and left clicking moves backwards I decided to colour the lines depending on the distance from the front left This is to allow the viewer to distinguish between the lines and is of no other significance the reason I mention this here is because every time I demonstrate this to anyone it is the first question they ask Fig 13 2 2 shows version 0 1b This version is very similar to vO 1a but with a few differences Most obviously the polygons are filled rather than wire frame but also
79. the air rather than to the ground and use this speed when 26 Aspects of Realism Golf Simulation Matthew Winchester calculating the effect of air resistance and spin Fig 6 3 1 shows 2 examples of the speed of a ball relative to the air in wind 1 Example A 4ms Ball gt 7ms i Relative _ gt Wind 3ms Example B Relative 4ms Ball 3ms Wind Figure 6 3 1 Shows the speed of a ball relative to the air accounting for wind 6 4 Density Temperature Pressure amp Humidity Density temperature pressure and humidity are all factors that affect the resistance coefficient of the air However for the purposes of this simulation we can simply assume that these factors will be constant Doing this simply enables a single constant value for the resistance coefficient to be set and we can then forget about density temperature pressure and humidity 6 5 Effects of spin in flight One of the major factors that affects the trajectory of a ball projectile is spin If you have ever watched any ball sport you will have noticed this Footballers use spin to curve the ball around players and tennis players use topspin to force the ball to dip so that they can hit the ball hard without it soaring out of the court In the game of golf spin can be imparted onto the ball by slicing across the ball as it is being struck This spin greatly affects the way the travels both in the air and on the groun
80. the diagram shown in Fig 6 7 1 gravity is responsible for the effect of the ball accelerating down the slope As we will only ever be dealing with the movement of one object the ball we can assume m Mass to be 1 therefore mg g We can now deduce the formula to calculate the resultant force directed down the slope as follows F sin O E F gsin 0 30 Aspects of Realism Golf Simulation Matthew Winchester Another of the main forces to consider when modelling the rolling of the ball is friction Friction is a force that arises due to resistive forces between the moving object and the surface it is moving over It is directed in the opposite direction to the motion of the object The magnitude of this force is relative to the normal reaction on the object from the surface If you look back to Fig 6 7 1 you will see that on a sloped surface the normal is calculated as N g cos 0 again assuming that Mass 1 Whereas on a flat surface N will simply be equal to g This can be proven since cos 0 1 The equation to calculate the magnitude of this force is F uN where u The coefficient of friction between the 2 specified surfaces The final factor affecting the rolling of the ball is spin The types of spin and the relevant effect is shown below Top Forward Back Backward Right Very Slight Right Left Very Slight Left Top amp Right Forward amp Right Top amp Left Forward amp Left Back amp Right Backward
81. thin the bounds of the second polygon 16 Aspects of Realism Golf Simulation Matthew Winchester Figure 4 2 3 Collision Detection using Bounding Spheres Figure 4 2 4 Collision Detection using Intersection Here there has been no collision Both of these methods are considerably time consuming and surely there must be a more simple method with a shape as simple as a golf course This brings me to my own idea a polygonal mesh with a set structure 4 3 Structured polygonal mesh This is an idea of my own My idea here is that the terrain is built out of polygons that follow a strict set of rules These being that the vertices adhere to a strict grid with only the height being variable fig 4 3 1 shows what I mean The most obvious disadvantage of this type of representation is that it is very inflexible It can be made more accurate by having smaller gaps between the grid but it will still lose accuracy when used to represent steep surfaces see fig 4 3 2 17 Aspects of Realism Golf Simulation Matthew Winchester Long gaps gt 3 between vertices Short gaps between ae vertices Figure 4 3 2 Shows how the accuracy is lessened on slopes There is however a huge advantage to this way of representing the map and that is the collision detection In an all purpose 3D engine it may not have much of a benefit but in this program the only thing that is going to collide with the map
82. ticular programming problem also known as Hitting a Brick Wall Aversion Strategy It is an almost certainty that during this project I will encounter a problem where the solution is not immediately obvious or encounter a bug where the reason is not immediately obvious In these situations I must not waste too much time on them I think that I should set a 2 hour limit on fixing any single problem and then I should go and work on something else Finding something else to do will not be a problem as I am going to have to be working on at least 3 or 4 things at a time throughout the running of this project 51 Aspects of Realism Golf Simulation Matthew Winchester 13 Map Modelling and Representation I have decided to make a small change to my original plan I was going to implement the map representation within the same tester application as the Ball Travel I have now decided that it would be better to develop the map representation techniques as an application in it s own right This has simplified things somewhat and I can now develop this application much more rapidly without worrying about it fitting in with everything else just yet 13 1 Map Representation As stated in the research section I decided to represent the map as a structured polygonal mesh The structure I decided to use is shown in Fig 13 1 1 To store the necessary information I decided to store all of the points in a single array The reason that I store
83. to seem like they are far more detailed Figure 4 2 2 demonstrates this See 5 2 Texture Mapping for more detailed information Figure 4 2 2 Texture mapping can make a rough representation look very realistic Pictures from University of Cambridge Department of Engineering http svr www eng cam ac uk research vision photobuilder recon html The main advantage to the freeform polygonal mesh is that it can represent almost anything However when it comes to collision detection detecting when 2 objects have come into contact there is no simple method There are several methods that can be used These methods include Bounding Spheres See Fig 4 2 3 and Intersections See Fig 4 2 4 Bounding Spheres is a method in which each polygon is surrounded by a theoretical sphere that contains every point of that polygon Collision or possible collision is detected when the distance between 2 objects possibly a single polygon is less that the sum of the radii of the objects Intersection based collision detection works by checking if any edges of one polygon pass through the surface of another This is a complex process and so is most often made into a 2 stage process The first check is to see if the any edge of the first polygon passes through the plane of the second This is a much faster process and acts as a check to see if the collision was possible if it was then continue with the second check checking if the intersection is wi
84. ur Code Description Priority Notes 2 1 1 The golf course must be able to represent sloping in any direction with any gradient 5 It must be possible to calculate the y coordinate height for any specified x and z coordinates Horizontal plane 5 The contour must be of sufficient detail e g high frequency of polygons to allow smooth travelling over curved parts of the course The display engine should make it possible for the user to be able to see the contour The contour of any part of the course that is water should be completely flat It must be possible to calculate the orientation of the slope at any point on the map The course must have a boundary Balls struck beyond that boundary must be considered out of bounds 45 Aspects of Realism Golf Simulation R2 2 Map Texture Matthew Winchester Code Description Priority Notes 22 1 The golf course must be able to be composed of at least the following textures Long Grass Medium length grass Short Grass Sand as in a bunker sand trap Pond Lake 5 Davee Rough should have the following properties a It should offer high resistance to balls rolling over it b It should absorb a lot of energy when the ball impacts on it c It should be displayed in a different colour to other textures and dark green is recommended d Striking the ball from the rough sh
85. w Figure 17 2 6 Screenshot The ball was putted 17 3 Skipped Requirements The vast majority of the requirements have been satisfied However a few have not These are detailed below along with the reason for skipping them R2 1 7 The course must have a boundary Balls struck beyond that boundary must be considered out of bounds I have not implemented this requirement purely due to lack of time It is not at all technically difficult and could easily be implemented in future R3 1 3 When the ball is struck into water or out of bounds they may replay the shot from the same position or take a drop ball at the nearest legal position to the place where the ball went out of bounds Again this was not implemented due to time constraints There is no technical difficulty in implementing this 74 Aspects of Realism Golf Simulation Matthew Winchester R3 2 5 The putter should only be used when the player is on the green and should be automatically selected for the user Once again this requirement was skipped due to time constraints rather than technical difficulty R5 0 1 The golf course should include various real world objects that may include bushes trees fences and signposts R5 0 2 The ball should interact with these real world objects in a realistic way These 2 requirements were skipped due to time constraints The technical difficulty of these 2 requirements is fairly high Adding the objects into the scene wou
86. w Winchester Water It is very rare that a ball struck into water will escape For this reason it is not necessary to model the properties of water I will simply assume that the shot is over as soon as the ball contacts water 5 6 Decisions For the purpose of this project I believe that simple light shading of solid colour will be sufficient This will result in the golf course not looking quite as realistic as it could have but the graphics engine will run a lot quicker It will also be a lot quicker to develop and with time being so limited this is probably the most sensible choice The easiest way to achieve this is to have a single light source the sun and vary the colour of the polygons that make up the golf course depending on the angle between them and the light This loss in realism is acceptable because the main focus is on the realism of the implemented physics rather than the display engine 24 Aspects of Realism Golf Simulation Matthew Winchester 6 Research Ball Travel The modelling of the ball travel is a major part of this project This includes calculating the flight of the ball the bouncing of the ball and the rolling of the ball Each of the major aspects that affect these things are researched below 6 1 Equations of motion There are a few simple equations that are used to calculate linear motion These are as follows v u at u v at s ut hkat s vt Y a t y ue 2as
87. wCongrat Fa isPutted resetPolyCount PcrawWind Fi getDistanceToPin translate a setupButfer rotateView drawP olygon setupClubUl ValterWind setEngine rupdateDistance getWind storePos nextStroke heag t Flag theWindy j view lastPos Wind rootNode clubs fagPositiony A eR theMap GolfClub Point3D PolygonTreeNode left Map Figure 15 1 1 Class diagram showing the main structure of the system 60 Aspects of Realism Golf Simulation Matthew Winchester Object3D InsaneTools DEPTH double 550 translate drawPolygon crossProduct Y gfaddNode polygonSource dotProduct N Ta getAngle oe Le getLength getTriangleDist Ball PolygonTreeNode getVector Map y Flag sist double matrixMultiply polygonindex int moveMatrix va PoS gt m ae oumPolys int resizeMatrix SOS PolygonTreeNodel rotationMatrix WIDTH int 75 Flag addNode i EE MiextureType short drawPolygon il triangleFacing translateOriginal draw left draw Map translate R collided translate right collided isOnScreen collided drawTriangle collided SoetY ye getArea getCoeffOfFriction getLengt

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