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Manipulation Using Magnet Metaphor for 2D and 3D

1. slots poy one of slots slots arent p D set lt slotname gt lt value gt gimme lt slotname gt update Fig 3 Standard messages among boxes Figure 2 shows messages between a display object and a model This is an example of RotationBox RotationBox has a slot named ratio that holds a double precision number which means a rotation angle Through direct manipulations on a box its associated slot value changes Furthermore its visual image simultaneously changes according to the s ot value change Then a box reacts to the user manipulations according to its functionality 3 2 Message sending protocol for slot connections Figure 3 illustrates a data linkage concept among boxes Each box has multiple s ots Its one s ot can be connected to one of the slots of other box This connection is called slot connection The slot connection is carried out by three messages 1 e a set message a gimme message and an update message when there is a parent child relationship between two boxes These messages have the following formats 1 Parent box set lt slotname gt lt value gt 2 Parent box gimme lt slotname gt 3 Child box update A lt value gt in a format 1 represents any value and a lt slotname gt in formats 1 and 2 represents the user selected slot of the parent box that receives these two messages A set message writes a child box slot value into its parent box slot A gimme
2. This paper also proposes the construction of such 2D interfaces using 3D primitives The new 3D component using a magnet metaphor also makes it easier to construct such 2D like 3D graphical user interfaces Key words Virtual Reality 3D toolkit 3D layout Object manipulation ntelligentBox 1 Introduction This paper proposes a 3D object manipulation method using a magnet metaphor for 2D and 3D integrated toolkit systems The authors have been studying 3D software development systems The research group to which one of the authors previously belonged has already proposed a component based 3D graphics software development system called ntelligentBox 1 2 IntelligentBox provides 3D software components called boxes Each box has a 3D visible shape and a unique functionality JntelligentBox also provides a dynamic data linkage mechanism called s ot connection With this mechanism the user can construct 3D graphics applications by combining existing boxes through direct manipulation on a computer screen without writing any text based programs Actually for the development of 3D graphics applications the layout of 3D objects is important factor However it is very laborious work and it takes a long time because 3D objects have six degrees of freedom DOF and it is not easy to lay out them using a standard 2D input device 1 e a mouse device In the real world every object exists contacting with other objects and usually it has thr
3. ICAT 2003 A 4 4 December 3 5 Tokyo JAPAN w Merere VIRTUAL REALITY SOCIETY OF JAP Manipulation Using Magnet Metaphor for 2D and 3D Integrated Toolkit Systems Yoshihiro Okada Yoshiaki Akazawa and Koichi Niijima Graduate School of Information Science and Electrical Engineering Kyushu University 6 1 Kasuga koen Kasuga Fukuoka 816 8580 JAPAN fokada y aka niijima i kyushu u ac jp Intelligent Cooperation and Control PRESTO JST Abstract This paper proposes a component based 3D object manipulation framework using a magnet metaphor for 2D and 3D integrated toolkit system The authors have been studying component based 3D software development systems For the development of 3D graphics applications the layout of 3D objects is important factor However it is very laborious work and it takes a long time because 3D objects have six degrees of freedom DOF and it is not easy to lay out them using a standard 2D input device 1 e a mouse device In the real world every object exists contacting with other objects and then it has three DOF i e x y translation and z axis rotation because the gravity exists Then the authors introduced new component that behaves like the magnet to simulate the simplified gravity effect for positioning 3D objects Furthermore 3D graphics applications need 2D graphical components for the interface of interactive operations e g pop up menus toggle buttons pull down menus and so on
4. age like VRML 5 When developing 3D graphics applications developers have to make programs to define the behavior of each object existing in a 3D virtual world using a script language As well there are some distributed Virtual Reality systems such as MASSIVE 6 dVS dVISE 7 DIVE 8 Although X Y translation Fig 1 Three DOF of the object contacting with on other object these are very powerful systems it is not easy to use their essential mechanisms for end users Our research system JntelligentBox provides various 3D software components represented as visible manually operable and reusable objects Furthermore IntelligentBox provides a dynamic data linkage mechanism called s ot connection These features make it easier for even end users to develop interactive 3D graphics applications This is the main difference between ntelligentBox and others Concerning the higher DOF problem for 3D object manipulations there are researches on the use of higher DOF input devices For example the Roller Mouse a three DCF mouse 9 the Bat a six DOF mouse 10 and Data Glove exist These devices allow the user to manipulate 3D objects as if he she would do in the real world However these devices have two main problems One is that these devices have their own manual operation way so the user suffers from the difference among such various ways The other one is that specialized hardware is expensive and difficult to get Sm
5. e a bookshelf has several shelves its inside so it is impossible to locate books on its shelves Figure 10 shows one of the solutions to this problem Each shelf should be an individual component and a parent child relationship should be assigned between any two adjoining shelves In such a case with using keyboard operations the user can put a book on any shelf Indeed we have already proposed a random layout algorithm for 3D scene generations 16 17 Figure 11 shows four random layout results generated by the algorithm However to obtain user required 3D scenes by modifying the 3D scenes once generated by the random layout algorithm user s manual operations are necessary In such a case 3D object manipulations using MagnetBox must reduce the cost of such layout work drastically ChildBox ParentBox ChildBox ParentBox ChildBox ParentBox Parent child relationship Hierarchy Fig 10 Positioning books in a bookshelf using MagnetBox Fig 11 Four random layout results generated by a prototype system 5 Virtual desktop construction of 2D like 3D GUIs 3D graphics applications need 2D graphical components for the interface of interactive operations e g pop up menus toggle buttons pull down menus and so on Our MagentBox help us to construct such 2D like 3D GUIs 5 1 3D Primitives 3D primitives of a screen image of Figure 12 are RotationBoxes SliderMeterBoxes ListBoxes and so on With us
6. e of its parent object like the sequence of position shown at each frame time As explained above usually 3D object moves on the surface of its parent object However there is the case that a desk exists on a floor and the target object also exists on the floor and the user wants to move the target object onto the desk Also there is the opposite case that the target object exists on a desk and the user wants to move it down onto the floor Our implementation makes it possible by using a keyboard operation Figure 8 a and d show the former case and the latter case respectively When the user clicks a specific key of a keyboard e g a u key the 3D object goes down under the desk as shown in Figure 8 d On the other hand when the user clicks another key e g a u key the 3D object goes up on the desk as shown in Figure 8 a Moreover in this case if the user clicks a u key again the 3D object goes upon the object located on the desk as shown in Figure 8 b From this situation if the user clicks a d key again the 3D object goes down onto the desk as shown in Figure 8 c In the all cases the target object once goes up to the position from the initial position Q and then goes down until it touches any other object Strictly speaking when the user clicks a w key 1 e the cases a and b MagenetBox moves the target object up to the position and then moves it down until it
7. ee DOF i e x y translation and z axis rotation as shown in Figure 1 because the gravity exits Therefore in order to make the layout of 3D objects easier we introduced a gravity field effect as a software component 1 e a particular box called MagnetBox into IntelligentBox Indeed the simulation of the complete gravity is impossible in real time so our MagnetBox only behaves like the magnet and it works in real time This is a 3D visual component so the user can adequately use it for his her applications in various ways For example this enables to provide a virtual 2D desktop On this desktop the user can lay out 3D primitive parts to build 2D like 3D GUIs as if he she would construct 2D GUIs on a 2D desktop As a result our system ntelligentBox came to have aspects of 2D and 3D integrated toolkit systems The remainder of this paper is organized as follows Section 2 discusses related work Section 3 explains essential mechanisms of JntelligentBox Section 4 explains how MagnetBox works and shows several construction examples of 3D composite models Section 5 explains the construction of 2D like 3D GUIs Finally section 6 concludes the paper 2 Related work Our research purpose is to clarify software architecture that makes it easier to develop interactive 3D graphics applications Its related works are Virtual Reality construction toolkit systems including MR Toolkit 3 MERL 4 and so on Most of them provide a script langu
8. ing MagnetBox the user can lay out them to build 2D like 3D GUIs as if he she would manipulate on the real desktop of a computer display like pasting peeling operations This reduces the time consuming for building 2D like 3D GUIs 5 2 Composition example of 2D like 3D GUIs Figure 13 shows one composition example of 2D like 3D GUIs and its hierarchical structure In the figure the symbols ratio state alpha value and opacity mean slot values of boxes The root object is IOBufferBox and its alpha value slot is connected to the ratio slot of RotationBox and also connected to the ratio slot of SliderMeterBox The opacity slot of the IOBufferBox is also connected to the state slot of ToggleSwitchBox The ToggleSwitchBox controls availability of the opacity of the JOBufferBox As well both the SliderMeterBox and the RotationBox works to change the transparency level of the OBufferBox To understand how this composite box works in more detail see the demonstration video on the web of 9 052000 Fig 12 Virtual desktop positioning 3D primitives by pasting peeling operations Fig 13 Composition example of 2D like 3D GUIs ICAT2003 conference or on_http www 1 kyushu u ac jp okada extern Publication ICAT2003 index html 5 3 VisorControlBox To provide a virtual desktop another box called VisorControlBox 1s used with MagnetBox in practical cases VisorControlBox controls the view direction in order t
9. ing the right button of object translation Y Sg a PS i E ee f P a viewpoint L Fig 4 Standard coordinate system n Aash Hy B ee 4 004006 _ ee el s 001000 x translatio Fig 5 Standard translation operations in IntelligetnBox select of two faces Fig 6 Moving an object to make its face touch the face of other object a mouse device corresponds to the z translation These X y and z axes mean the screen coordinate as shown in Figure 4 With these translations it is still difficult to put 3D objects on other object and move on it Indeed IntelligentBox provides three dedicated operations for such a case One is to move a 3D object to make its specific face touch the specific face of other 3D object as shown in Figure 6 Actually this operation needs extra operations to select the two specific faces The remaining two are to move and to rotate a 3D object on its specific face as the same as shown in Figure 1 These operations need many menu selections This is not convenient and not intuitive manner Furthermore it needs many set of operations for positioning 3D objects especially on a composite object composed from several primitive objects MagnetBox makes it simple as follows 4 2 Functionality of MagnetBox As mentioned in Sec 1 MagnetBox has not a real gravity effect but a magnet effect That is each 3D object defined as a descendant
10. ith et al 11 proposed the manipulation of 3D objects using a 2D user interface This system employs contact constraints among 3D objects to allow the user to position 3D objects using a mouse device Xu et al 12 proposed a constraint based automatic placement system using the pseudo physics engine 13 The purpose of these researches is the same as that of our research However the approach of our research is different from the others In this paper we propose the component based approach 3 Essential mechanisms of ntelligentBox IntelligentBox employs the following essential mechanisms inherited from J ntelligentPad 14 15 which is a 2D synthetic media system because JntelligentBox 1s an extension of JntelligentPad to 3D graphics applications 3 1 Model Display object MD structure As shown in Figure 2 each box consists of two objects a model and a display object This structure is called an MD Model Display object structure A model holds the state values of a box They are stored in variables called slots A display object defines how the box appears on a computer screen and how the box reacts to user operations Display object X RotationBox User event visible Model invisible 4 getting a slot value to change a shape update propagation to tell state change Rotation Fig 2 MD structure of a box and its internal messages child child messages Ae
11. message reads a parent box slot value and sets it into its child box slot Update messages are issued from a parent box to all of its child boxes to tell them that the parent box slot value has changed Each box has three main flags that control the above message flow 1 e a set flag a gimme flag and an update flag These flags are the properties of a display object A box works as an input device if its set flag is set to true Contrarily a box works as an output device if its gimme flag is set to true A box sends update messages if its update flag is set to true Then child boxes take an action depending upon the states of the set flag and the gimme flag after they receive an update message or after they individually change their slot values 4 3D object manipulation using magnet metaphor In this section we introduce standard 3D object manipulations supported by IntelligentBox and describe their problem when positioning 3D objects Then we explain how MagnetBox works in IntelligentBox to compensate it and shows several positioning examples 4 1 Standard manipulation of 3D objects Figure 4 shows the standard coordinate system of 3D graphics systems JntelligentBox also has the same coordinate system Figure 5 shows standard translation operations in ntelligentBox The left right movement of a mouse device corresponds to the x translation its up down movement corresponds to the y translation and the up down movement with push
12. o keep it as the same as the normal direction of the magnet face of MagnetBox With VisorControlBox the user sees 2D like 3D primitive components on the magnet face as if they would exist on a 2D flat display screen 6 Concluding remarks This paper proposed a component based 3D object manipulation framework using a magnet metaphor for 2D and 3D integrated toolkit systems By considering the gravity it is possible to reduce the DOF of 3D objects and to make the positioning of 3D objects simple We introduced a particular component called MagnetBox into IntelligentBox in order to simulate the simplified gravity effect MagnetBox is also used to provide a virtual desktop in a 3D space and hence is useful for the construction of 2D like 3D GUIs In this paper we explained how MagnetBox works and describe its usefulness The functionality of MagnetBox is based on the collision detection Since we do not use any efficient collision detection algorithm we will have to introduce one of the efficient collision detection algorithms to improve the performance of MagnetBox Furthermore we will have to develop some practical application examples of 2D like 3D GUIs to evaluate the availability of MagnetBox These are our future works References 1 Okada Y and Tanaka Y JntelligentBox A Constructive Visual Software Development System for Interactive 3D Graphic Applications Proc of Computer Animation 95 IEEE Computer Society Press p
13. of MagnetBox always touches its parent object When through the manual operation using a mouse device the user translates any 3D object that is a descendant of MagnetBox the 3D object moves on the surface of its parent object like a creeping motion as shown in Figure 7 a Normal arrow time t t i t 2 t 3 wf OR IO dv a 5 gamer ot A ae 7 orma XCM ean Me direction MagnetBox a time t t t 2 t 43 F f ENA i n f aster a f os v de oe ex D EO l b Normal direction Magnet face MagnetBox Fig 7 Moving an object with touching the surface of its parent object parent Magnet face MagnetBox eee MagnetBox Magnet face normal direction MagnetBox Magnet face d y 0 parent MagnetBox Magnet face Fig 8 Object positioning example using MagnetBox lines mean the movement of a 3D object by a standard translation operation t t 1 t 2 and t 3 mean frame times In each frame the standard translation operation executed by the user moves the target object to the position and then MagnetBox once moves it to the position where is enough high from the magnet face and moreover moves the target object down until it touches its parent object or its ancestor object shown in Figure 7 b A magnet face is the user specific face of MagnetBox Finally the target object will be located at the position As a result the target object moves on the surfac
14. p 114 125 1995 2 Okada Y and Tanaka Y Collaborative Environments in J ntelligentBox for Distributed 3D Graphic Applications The Visual Computer CGS special issue Vol 14 No 4 pp 140 152 1998 3 Shaw C Green M Liang J Sun Y Decoupled Simulation in Virtual Reality with the MR Toolkit ACM Transaction on Information Systems Vol 11 No 3 pp 287 317 1993 4 Anderson DB Barrus JW Howard JH Rich C Shen C Waters RC Building Multiuser Interactive Multimedia Environments at MERL IEEE Multimedia 2 4 77 82 1995 10 11 ae 13 14 15 16 Ly Ames A L Nadeau D R and Moreland J L The VRML Sourcebook John Wiley amp Sons Inc 1996 Greenhalgh C Benford S MASSIVE a Distributed Virtual Reality System Incorporating Spatial Trading Proceedings of IEEE 15th International Conference on Distributed Computing Systems DCS 95 pp 27 34 1995 Grimsdale Ce dVS Distributed Virtual Environment System Proceedings of Computer Graphics 91 London UK Bleinheim Online pp 163 170 1991 Hagsand O Interactive Multiuser VEs in the DIVE System IEEE Multimedia Vol 3 No 1 pp 30 39 1996 Venolia D Facile 3D direct manipulation ACM SIGCHI pp 31 26 1993 Ware C and Jessome D R Using the Bat a six dimensional mouse for object placement JEEE computer Graphics amp Applications 8 6 pp 65 70 1988 Smith G Salzman T and Stue
15. rzlinger W Integration of constraints into a VR Environment VRIC 2001 pp 103 110 2001 Ken Xu James Stewart Eugene Fiume Constraint based Automatic Placement for Scene Composition Graphics Interface pp 25 34 2002 M Shinya and M C Forgue Laying out objects with geometric and physical constraints The Visual Computer 11 188 201 1995 Tanaka Y Meme Media and a World Wide Meme Pool Proc of ACM Multimedia 96 pp 175 186 1996 Tanaka Y Meme Media and Meme Market Architectures for the Reediting and Redistribution of Knowledge Resources Proc of MultiMedia Modeling 98 IEEE Computer Society Press pp 2 11 1998 Akazawa Y Okada Y and Niyima K Automatic 3D Object Placement for 3D Scene Generation The European Simulation and Modeling Conference 2003 ESMc2003 short paper pp 316 318 2003 Akazawa Y Okada Y and Niyima K 3D Scene Generation System and Its Intuitive Interface to appear in EUROSIS 4 annual European GAME ON Conference GAME ON2003 2003
16. touches any sibling object On the other hand when the user clicks a d key 1 e the cases c and d MagnetBox once moves the target object up to the position and then moves the target object down until it touches any ancestor object of its parent As you see figure 8 and imagine these operations also change the parent child relationship concerning the target object automatically For example in the case of Figure 8 a after the operation the target object becomes the child of the desk If the user moves the desk the target object still moves with attached to the desk In the case of Figure 8 b after the operation the target object becomes the child of the object located on the desk 4 3 Discussion Figure 9 shows an actual layout example Usually without using MagnetBox it takes a couple of minutes to compose the composite component of the right figure from separate primitive objects of the left figure However with using MagnetBox it takes less than one minute This is a very simple composition example and its elapsed time was very short However when making more complicated scene it needs longer time In such a case the use of MagnetBox comes to have the big a b Fig 9 Composition result b composed from primitive components a advantage There is a problem because for simplicity our algorithm cannot detect the collision of a target object with inside faces of other object For exampl

Manipulation Using Magnet Metaphor for 2D and 3D

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