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GemCad User`s Manual

1. for CGA e for EGA h for Hercules v for VGA This will bypass the auto detection software and will hopefully get things going in the right direction GemCad can be driven with the function keys legends for which appear at the left of the screen Legends beginning with gt change to anew menu of functions You can also point at a function key legend with the mouse and click a mouse button to activate it The Help h key Function key F11 or Shift F1 in every menu followed by another function key will print a short description of what that key does when it is NOT preceded by the F11 key To install the program onto your hard disk I recommend making a subdirectory called GEMcAD on your hard disk and then copying all of the files to that directory If your hard drive is c and your floppy is A do the following at the DOS prompt CG CD MD GEMCAD CD GEMCAD COPY A GemCad Tutorial Lesson 1 To run GemCad type GEMcaAD at the DOS prompt GemCad will print its version number and copyright notice After you press any key or mouse button to acknowledge the message GemCad will switch your display to the graphics mode Your display should then look something like Figure 1 BOTTOM Figure 1 Display when GemCad is first run This is an actual screen dump with a VGA display An EGA display will look slightly less resolved vertically and a CGA will look considerably less resolved vertically The screen
2. 64 tooth gear when first run After you press the Index gear g key GemCad will prompt you to enter the number of teeth on the index gear GemCad has provision for clockwise and counter clockwise orientations Gears with positive numbers of teeth increase counter clockwise and gears with negative numbers of teeth increase clockwise Next GemCad will ask you for the offset This is the index which will appear at the bottom of the circle of numbers in the Top View An offset of zero causes the I D position to be at the bottom and an offset of half the number of teeth of the gear cause the I D position to appear at the top Pressing Enter without entering an offset also makes the I D position to appear at the bottom The number of teeth must be a whole number but the offset may be fractional command Symmetry y Change the degree of radial symmetry and whether mirror image symmetry The Symmetry y command allows you to tell GemCad how many facets make up a tier and are cut at the same angle and cutting depth mast height GemCad will prompt you for the degree of radial symmetry and whether or not the stone has mirror image symmetry The stone and index gear will then be redrawn The degree of radial symmetry is the minimum number of facets which will be cut at once Facets at an angle of zero are the only exception to this rule since they can be cut at any index If the stone has mirror image symmetry twice as many facets as the degree of
3. BOTTOM Figure 3 Positioning the cursor to pick the girdle line Press the Pt on edge e key This causes GemCad to look in the view containing the cursor is for the edge nearest the cursor The cursor does not have to be exactly on the edge it will snap to the nearest edge If the x y z coordinates GemCad prints are close to 0 0 1 0 0 0 enter y in response to the question about whether to use the point GemCad will ask you this question whenever you enter a point with any of the commands in the Point Menu You should see the message 1pt in the status box at the lower left hand corner of your screen What if you enter y to use a point when you didn t mean to If you redraw the stone with the Draw d key in the Cut Facets Menu or Point Menu all points the angle and the index will be discarded The status box will display the total number of facets Now we can tell GemCad at what index to cut the mains Press the gt Cut Menu key Next press the Index i function key Enter 0 Index position 0 is the same as index position 64 You should see the message ipt 10 0 in the status box Now press the Angle a key and enter the pavilion main angle 44 GemCad will then proceed to cut the eight main facets Redraw the stone with the Draw d key Your screen should look like Figure 4 The Draw d command updates the dimension lines The List to sern 1 command gives the numerical values of various ratios of the dimensions indicated by
4. Enter an angle of 90 degrees and set two consecutive points on the girdle outline with the Pierce zero p command GemCad will cut the resulting facet If you go all the way around the girdle outline in this fashion you will cut a preform of girdle facets at 90 with the same outline as your drawing The indexes of the resulting facets will not be whole numbers however You can use the Change C command to change the index of each facet to a whole number You then cut facets around the stone to a temporary center point working in the Side and End Views These facets must be at the same indexes as the girdle outline facets to make a level girdle You can use the Jam index j command to duplicate the index of the facet surrounding the cursor This makes what is commonly referred to as a C A M Centerpoint Angle Method Preform command Query user q Query user for x y and z coordinates of a point of a new facet If you know the x y z coordinates of a point on a new facet the Query user q command allows you to enter the numerical values of the coordinates directly from the keyboard GemCad will prompt you for each of the three values in turn When cutting a C A M preform it s sometimes best to start with the point 0 0 1 For convenience the Draw d Zoom z and Undo u commands are also found in the Point Menu They are described above in the section on the Cut Facets Menu The Edit Menu Most of the commands in the Cut
5. This immediately does an undo The Escape key will also interrupt the Kill facet k or Kill tier K key commands If a new facet misses the stone entirely GemCad will sometimes draw a stone within a stone The way out of this is with the Undo u key What if you ve already changed the stone so that the undo key doesn t get rid of the phantom facets You can position the cursor inside the phantom facet press the Blink facet b key and make sure only the phantom facet blinks and then kill the facet or tier with the Kill facet k or Kill tier K keys It might be necessary to move to a different view or to rotate the stone with the Rotate Tilt r key to specify the phantom facet unambiguously Again before using the Kill facet k or Kill tier K keys to kill a phantom facet check first with the Blink facet b key to make sure GemCad will kill the facet you want it to kill Last resort If things are totally hopeless if your two year old has pressed the red reset button or if there has been a power failure there is still hope Restart your computer change directories to where you were when you last ran GemCad run GemCad and execute the Undo u key This will read in the file GEMCAD BAK and get you back to one step before the catastrophe It is important to do this before reading in any other file or cutting any new facets since any command that changes the stone will overwrite the file Using GemCad with a Mouse Ver
6. View GemCad will pick this point of intersection Otherwise GemCad will project the plane of the facet and compute the point of intersection with the z dop axis GemCad will ask you if you want to use the point command Pierce zero p Set a point of a new facet where the cursor pierces the zero plane This is the probably the most difficult of the point commands to understand but it is seldomly used Each of the four views shows a projection of the stone onto one of the three coordinate planes The Top View is the projection of the stone onto the x y plane The z axis is the axis of rotation of the dop In the Top View the p command will set the x and y coordinates to those of the cursor and the z coordinate will be set to zero In the End View the Pierce zero p command sets the x and z coordinates and the y coordinate is zeroed In the Side View the Pierce zero p command sets the y and z coordinates and the x coordinate is zeroed As with the other point commands GemCad will draw cross hairs print the x y z coordinates of the point and ask you if you want to use the point The Pierce zero p command is useful for making a preform from a sketch One method is to sketch or photocopy a sketch of the stone on a transparency and tape it to your screen Zoom in on the Top View with the Zoom z command and center the dop axis on the dot at the center of the Top View The sketch should have the girdle outline divided into line segments
7. a three button mouse the center button is mapped to the f point on facet command On a two button mouse pressing both buttons simultaneously will also perform the Pt on facet f command When GemCad is prompting you for input at the top of the screen the left mouse button is mapped to the y key and the right button is mapped to the Enter key Thus to answer yes to a yes or no question press the left and then right mouse buttons To answer no enter a null response by pressing just the right mouse button The center button if present is mapped to a backspace Consider an example To set a meet point and use it to add a new facet move the mouse near the meet point press the left button mapped to the Meet pt m command GemCad will then ask you if you want to use the point Press the left button mapped to y and then the right button mapped to Enter You can set meet points points on edges and points on facets without touching the keyboard The cursor keys work exactly the same way with a mouse as they do without They are convenient for moving the cursor vertically or horizontally from another point on the screen There are two environment variables that pertain to the mouse when used with GemCad If you mouse seems to move two or more pixels in one axis or if the cursor keys don t seem to work in one of the four directions read further If you type SET MxDIv 2 at the DOS prompt prior to running GemCad the program will
8. and multiply the aspect ratio by the ratio of the width to the height If you select the HP compatible printer the aspect ratio is ignored since all of the HP printers have square pixels Error Recovery What if you press a key that executes a command that you didn t intend to Let s say you pressed the Angle a key by mistake GemCad will ask you to enter the angle If you just press the Enter key or the right mouse button GemCad will abort the command What if you enter an angle incorrectly and don t realize it until after you have pressed the Enter key Just press the Angle a key again this time entering the angle correctly What if you enter an angle when you meant to enter an index If you redraw the screen with the Draw d key GemCad will discard all data pertaining to new facets and will clear the status box in the lower left hand corner of the screen What if you accidently gave GemCad enough information to cut a facet that you really didn t want to cut You can wait until GemCad finishes and then use the Undo u key What if you tell GemCad to cut a facet that starts hacking away at your stone If a facet is cut off GemCad will tell you so in an error message telling how may facets were cut off You must then press any key to acknowledge the error message You may then use the Undo u key to uncut the facet If GemCad seems to be taking a long time to compute the new facets you may interrupt it by pressing the Escape key
9. cut If time lapse is on only facets changed by the addition of a new tier of facets are redrawn If time lapse is off the entire stone will be redrawn after the tier of facets is added The Utility Menu command Blink facet b Recompute the facet surrounding the cursor The Blink facet b command erases the facet surrounding the facet recomputes it and then redraws blinks it This is the quickest way to find out the angle and index of a facet they are printed in a box at the upper left hand corner of the screen command Blink tier B Recompute a tier of facets one of which surrounds cursor The Blink tier B command recomputes an entire tier of facets GemCad searches its database of facets and finds the one surrounding the cursor All facets belonging to the same tier as the specified facet are recomputed and redrawn blinked command Meas vector v Display distance angle and index of line joining last two points A vector is a quantity with magnitude and direction The Meas vector v command is used as a measuring stick It gives the length and direction of the line joining two points To use the Meas vector v command pick two points typically with the Meet pt m command or the left mouse button When GemCad asks you to use the points enter n or just press Enter Then press the Meas vector v key GemCad will print the distance between the two points projected along each axis and also give the true length of the line
10. end of the last lesson You can navigate through the directory tree by selecting the directories that end with the backslash character The special directory is the parent of the current directory and clicking on it moves closer to the root of the directory tree So when you locate your project move the cursor box around with the mouse or cursor keys to highlight your file name Then press a mouse button or the Enter key The stone should look the same as when you saved the project at the end of Lesson as shown in Figure 7 Now we are ready to cut more facets Press the gt Main Menu key to return to the Main Menu and then press the gt Cut Menu key to get to the Cut Facets Menu We shall now cut our crown mains at index position 64 at an angle of 40 Press the Index i key and enter 0 for the index Now enter the angle by pressing the Angle a key and entering 40 Now we must enter a point on the facet In order to see more clearly to position this facet precisely we can zoom in on the End View Move the cursor down to the girdle line on the End View Then press the Zoom z key GemCad will enlarge the End View to fill the entire screen Move the cursor to where you want the main at index 64 to meet the girdle facets decide how much girdle to leave by eye The cursor should be positioned as shown in Figure 8 y END A E Figure 8 Position the cursor to define the girdle thickness Press the gt Point Menu key Then
11. joining the two points Next GemCad will print the bearing angle and index of the line joining the two points One use for this feature is to figure out the minimum angle needed to cut off an edge command Set vector V Set units for Meas vector v command The Set vector V command is used to set the length of the measuring stick used for the Meas vector v command The main use of this feature is to allow you to measure the ratio of two lengths without having to divide the numbers yourself Let s say you want to measure the length of a feature on a design as a fraction of the width of the design First pick two points on opposite sides of the stone with the Meet pt m key But tell GemCad not to use the points for a new facet Next press the Set vector V key GemCad will print the length and direction of the line joining the points as in the Meas vector v command GemCad will then ask you along which axis you want the distance to be set and how many units long you want this segment to be For instance if you want your measuring stick set such that the width of the stone is one unit and your stone is longer than it is wide pick two points opposite one another at the widest point of the stone Press the Set vector V key Press Enter twice to acknowledge the length and direction in the old units GemCad will then ask you along which axis the length is measured that to you wish to set Next it asks how many new units long to set this di
12. left button is equivalent to a y and the right button is equivalent to the Enter key Thus pressing the left and then the right buttons is equivalent to a yes response and pressing just the right button is equivalent to a no response The number of points set so far is displayed in the box in the lower left hand corner of the screen The following section describes each point command in detail command Meet pt m Set a point of a new facet at the existing meet point nearest cursor GemCad will search its database of vertexes meet points of three or more facets and find the one nearest the cursor in the Manhattan sense sum of vertical and horizontal distances The cursor will snap to the meet point and GemCad will ask you if you want to use the point Since the exact meet point is determined by the equations for the planes of the facet the point is set to much finer precision than the resolution of the display you are using When the cursor is visible the left mouse button is equivalent to the Meet pt m command command Pt on edge e Set a point of a new facet on the edge of an old facet nearest cursor GemCad will search its database of edges of facets the intersections of two facets and find the one nearest the cursor in a vertical or horizontal direction The cursor will snap vertically or horizontally on the screen to the nearest edge and GemCad will print the x y z coordinates of the point and ask you if you want to use
13. of the stone onto the faces of a cube The advantage of cutting facets in the Top View is that the x coordinate is shared with the End View and the y coordinate is shared with the Side View Neither axis of the Bottom View aligns with any of the other views A word about correcting errors in entry Entering two different indexes will cause the first index to be discarded If you make a mistake entering the index simply enter it again If GemCad has just cut a facet that didn t come out as you hoped you can use the Undo u key found in several of the menus This will undo the previous command that changed the stone The Undo u command only undoes the last change to the stone The undo command will not undo itself If GemCad is busy cutting off facets or otherwise taking longer to do something than you might expect press the Esc key to interrupt This will automatically perform an undo Now back to our brilliant We shall cut the pavilion mains next We need to indicate to GemCad at what depth to cut the mains You specify the cutting depth of a facet to GemCad by entering one or more points on the facet to be You specify points to GemCad by moving the cursor around on the screen and by making choices in the Point Menu with the function keys Now go to the Point Menu by pressing the gt Point Menu key The cursor is located at the intersection of cross hairs on the screen that look like a sign To move the cursor around on the screen you can
14. press the Pt on edge e key to pick a point on the facet to be If the cursor snaps to the edge you wanted enter y to cut the facets Your display should look like Figure 9 Figure 9 After cutting the crown mains The mains meet at a point on the crown We re cutting cheap rough with an oversized preform We are now ready to enter information about the crown break facets The cursor should be near the meet point of the crown facet we just cut at index 64 and the girdle facets Since we want the break facets to meet here also press the Meet pt m key to select this meet point Enter y to use the point You should see the message 1pt in the status box Now we need to zoom back out to get the big picture Press the Zoom z key You should now see all four views again as shown in Figure 10 There are only two magnifications the zoom command toggles between the two TOP As WZ SIDE BOTTOM Figure 10 Zoom out to see the big picture Now we must decide how large to make the crown break facets Instead of entering the angle explicitly we shall let GemCad figure it out Li et s make a construction line to assist us in placing these facets The minus key the hyphen or is used to draw construction lines The Constr line command is also found in the Utility Menu Let s draw a line Move the cursor away from the stone and press the key Move the cursor again and press the key again GemCad will draw a dotte
15. the abbreviations BOTTOM Figure 4 After cutting the pavilion mains Now you might be wondering what the bottom of our stone is doing in the Top View Not to worry we will transfer the stone later Generally you will find it easiest to cut facets on the Top View You might also be wondering how GemCad knew to cut only eight main facets but sixteen girdle facets Since we are using mirror image symmetry index position 64 or 0 is mirrored by itself The same is true for the star facets which we will cut at index position 4 12 20 Now we will cut the pavilion break facets Instead of telling GemCad at what angle to cut the breaks we will tell GemCad where to cut the facet and have it figure out the angle The cursor should still be near the meet point of the main facet at the 64 index and the girdles in the End View You don t have to be right on the meet point just near it Press the key labeled gt Point Menu Now press the Meet pt m key The cursor should snap to the nearest meet point and ask you whether to use the point Answer with a y if GemCad has found the meet point of the girdles and the main at index 64 Now move the cursor to the Top View How far down do you like your pavilion break facets to extend Some faceters prefer about half way from the girdle to the culet I prefer them cut about two thirds of the way down to the culet Move the cursor wherever you desire along the right edge of the main at index 64 as shown
16. use either the arrow keys on the calculator style numeric keypad or the cursor keys if your keyboard has them The odd numerals 1 3 9 and 7 on the numeric keypad make the cursor move diagonally If the numeric keys on your keyboard are the same keys as the cursor keys it doesn t matter whether or not the Num Lock key is active Now experiment with moving the cursor around The cursor accelerates if held down that is the step size increases the longer you hold down a key GemCad can also make use of a Microsoft or compatible mouse most are If your mouse doesn t do anything its probably because you have not loaded the driver software supplied with your mouse See the section on mice at the end of the reference section of this manual Move the cursor down to near the center of the End View If you press the space bar GemCad will draw a pair of dotted lines across the screen intersecting at the cursor This allows you to line up things in different views Move the cursor so that it aligns horizontally with the dot at the center of the Bottom View and so that it aligns with the vertical edge of the girdle facet at the center the End View Pressing the space bar again will remove the previous cross hairs When the cursor is in the End View it specifies the x and z coordinates When it is aligned horizontally with the dot at the center of the Bottom View the z coordinate is zero Your cursor should be positioned as in Figure 3 TOP SIDE
17. used to provide a title designer and date The heading will show up at the top of the listing The completed design should look like Figure 39 BOTTOM Figure 39 I suggest that you try to cut the Form e Cross Rectangle from the faceting diagram included in the center of this manual Once you can cut the design from the faceting diagram without referring to the manual you should be well prepared to cut from other published diagrams This completes the tutorial section of the manual The next section is a reference manual that describes each GemCad command in detail GemCad Reference Manual The File Menu The commands in this menu are to read and write disk files GemCad deals with three types of files There are a pair of commands to read and write each type command Open O Open an existing project read from a binary file The Open O command is used to open an existing GemCad project file Such a file is a binary file saved previously with the Save s or Save as S command GemCad will prompt you for the name of the file You may either type in the file name or just press the Enter key to use the file picker If you type in the file name the file must be in the current directory or a full or relative path must be given such as C CUTS bril gemor QUARTZ cut gem If there are already facets cut GemCad will ask permission to trash them before asking you for the file name If you press the Enter key to use the fil
18. 4 and the star facets Press the Meet pt m key As soon as you enter y GemCad will cut the table Note that you only had to enter the angle zero and not the index since index has no meaning for angle zero You should now see the completed brilliant cut on your display as in Figure 15 TOP SIDE BOTTOM Figure 15 The crown is complete This completes our round brilliant Note that the only angles we had to enter were 44 for the pavilion mains 40 for the crown mains and 90 for the girdle facets The remaining angles were set by eye by picking points along existing edges or on existing facets This is often the way you will work when designing a new cut This completes Lesson 2 the crown of a round brilliant Be sure and save the stone Press gt Cut Menu key the gt Main Menu key and then the gt File Menu key Then press the Save s key Since we specified the project name when we opened it GemCad will not ask you for a file name GemCad will tell you that the file already exists and ask you if it s O K to write over the file After saving the project quit the program by pressing the Quit Q key GemCad Tutorial Lesson 3 In this lesson we will find out how to make a cutting schedule We will also optimize the angles for quartz Open the project to read our brilliant back from disk Now change to the Diagram Menu To list out the cutting schedule press the List to sern I key Let s study this for a moment GemCad will
19. G in the current working directory When GemCad is first run it tries first to find a file called GemcaD cre in the current working directory If it cannot find such a file it looks in the same directory in which the GEMCAD EXE resides for a file named GemcabD crc If it can t find either configuration file it just uses the defaults built into GEMCAD EXE You can therefore make a generic configuration in the same directory where GemCad resides and then make different directories for special situations The questions about margins and headers pertain to the format of the listing produced with the List to file L command The List to file L command is set up to make a listing that can be printed with the diagram produced with the GemPlot GemJet or GemDot programs These programs produce publication quality diagrams on various printers from your GemCad files They do not print the cutting instructions however Since the margins character pitch and line spacing vary with the type of printer GemCad allows you to adjust the print position of various parts of the diagram The first part of the listing is the header It contains the heading as entered with the Heading H command a tally of the number of facets some parameters and the dimensions of the stone The header is indented more than the cutting instructions that follow Blank lines follow the header so that the cutting instructions always begi
20. GemCad User s Manual Version 4 51 by Robert W Strickland May 1992 Revised August 24 1992 HTML version of manual December 14 2000 Dedication GemCad is dedicated to the memory of my father Robert L Strickland who introduced me to faceting Acknowledgements I gratefully acknowledge the many suggestions of Walter Carss Bob Long Norm Steele Greg Thompson I thank all of the GemCad users whose continued suggestions have helped me to improve the program I thank my wife Dorothy who let me put in the long hours on GemCad and helped me proofread this manual Copyright 1992 2000 Robert W Strickland All rights reserved Contents Introduction Tutorial Lesson 1 Lesson 2 Lesson 3 Lesson 4 Reference Manual File Menu Cut Facets Menu Point Menu Edit Menu Utility Menu Diagram Menu Configuring GemCad Error Recovery Using GemCad with a Mouse Introduction This manual describes GemCad 4 0 a computer aided design program to assist in designing faceted gem cuts GemCad simulates a faceting machine You can specify angles and indexes and GemCad will cut facets on the screen drawing the stone at each stage This is valuable for checking the validity of published faceting diagrams Although GemCad simulates a faceting machine its real purpose is to do the grunt work of designing new gem cuts GemCad can figure out the angle of a facet given two points and its index and it can figure out the angle and index given t
21. LIN program that comes with all versions of MS DOS and the EDIT program that comes with DOS 5 0 are examples of text editors command L amp S import M Import project from a Long amp Steele format file The L amp S import M command reads a project from a file compatible with the programs written by Robert Long and Norman Steele Long and Steele have compiled a vast library of facet designs and GemCad can import these files directly These files are text files and and have names that typically end with the P3D c3D or B3D extensions for pavilion crown or both GemCad will prompt you for the name of file If you just press the Enter key GemCad will bring up the file picker with the wildcard 3p It will then scan the file and draw the stone on the screen Next GemCad will prompt you for the symmetry of the stone just as in the Symmetry y command GemCad will name each tier with a number in the same order as it appeared in the data file GemCad will make the I D position of the index gear at the top of the screen If the stone is longer than tall you might have to scale it down with the Scale X to make it fit on the screen GemCad will print an error message if it encounters a facet with less than three sides Any error messages pertaining to the data file will begin with the line number in the data file at which the error was encountered command L amp S export E Export project to a Long amp Steele format file The L am
22. Menu change the stone in some way command Xfer x Transfer the stone The Xfer x command is used to transfer the stone The stone will be turned upside down What was in the Top View will be in the Bottom View You will find it easiest to do most cutting in the Top View This is because the Top View aligns horizontally with the Side View and vertically with the End View command Kill facet k Kill the facet surrounding the cursor The Kill facet k command deletes a single facet The facet is erased and the facets it used to share an edge with are recomputed and redrawn This can be a slow process on machines without numeric co processors command Kill tier K Kill a tier of facets one of which surrounds cursor The Kill tier K command kills an entire tier of facets The facets are erased and each facet that shares an edge with one of the killed facets is recomputed and redrawn This command can be quite slow on machines without numeric co processors command Center c Center the current view about the cursor The Center c command is used to center the stone about the cursor in the view containing the cursor Let s consider the End View The End View shows a projection of the stone in the x z plane with x increasing to the right and z increasing up the screen Let s say that your stone positioned too far up in the End View and you want to move it down Move the cursor inside the stone to its approximate center by eye and press t
23. ame already exists GemCad will ask you if it is O K to write over the file If the file does not yet exist the file will be created The data files that GemCad reads and writes may have any legal DOS file name eight characters or less plus an optional three character extension It s best for to name your GemCad files with names that have extensions beginning with g so that the file picker can find them without having to change the wildcard It is a good idea to save your work frequently when designing a new stone This is done with the Save s command With the Save as S command GemCad will always ask you for the file name whereas with the Save s command GemCad only asks if you haven t yet given it a name It will still ask if it s O K to write over an existing project however If you inadvertently exit the program without saving your work if the power should fail or forbid the program should crash you can still recover most of your work Run GemCad press Enter and then immediately press the Undo u key found in several of the menus This will get you back to just before the last change To save its work GemCad uses a file named GEMCAD BAK in whatever directory from which it was run It updates this file whenever you make a change to the stone Note that the undo command will not undo itself Lesson is now complete You might want to take a break now to let the stone and your brain cool off a bit If you have used
24. clear your screen and list the schedule The first line shows the name of the project The next shows the refractive index The next shows the total number of facets with and without the girdles Next come the symmetry of the stone and the index gear The next section gives the relative dimensions The abbreviations refer to the drawing of the stone Next comes the facet data Each tier of facets is shown on a separate line The angle of the tier in degrees is given and then the index of each facet is given All facets in a tier are cut at the same angle and cutting depth Unfortunately there is no way to tell which line goes with which tier We will remedy this shortly After you have viewed the listing press any key to redraw the stone Now let s name or label the facets Move the cursor inside the table in the Top View Press the Name n key GemCad will highlight the facet ask you for the name of the facet Enter T for table GemCad will then redraw the facet and label it with a T Names can be up to three characters long but one or two character names make for less clutter Name all the facets as shown in Figure 16 Figure 16 After naming all of the facets Now press the List to scrn I key to list the cutting schedule Now each line of the facet data begins with the name of the corresponding tier You can name two facets on a tier with different names but only one will be printed in the listing Now let s analyze the optical p
25. d line from the first point to the second point You can use the Draw d command to erase construction lines Position the cursor in the Top View near the meet point of the main at 64 and the girdle To help you position the cursor you can press the Meet pt m key to snap the cursor to the meet point Enter n or simply press the Enter key to discard the point Here we are only using the Meet pt m key to snap to the meet point quickly Press the key to begin our construction line Next move the cursor near the meet point of the main facet at index position 16 and press the Meet pt m key to snap to the meet point Press Enter to discard the point Next press the key to draw the construction line Now move the cursor near the intersection of the construction line and the edge formed by the intersection of the mains at indexes 64 and 8 The edge will align radially with the 4 index position Your cursor should be positioned as shown in Figure 11 TOP 44 48 52 T Al END BOTTOM Figure 11 Position the cursor to set size of mains If we enter a point on the edge at the intersection of the construction lines we will end up with about a 60 table If you want a smaller table move towards the center of the crown a bit When you have the cursor where you want it press the Pt on edge e key to set the point If the cursor moves only slightly to snap to the edge enter y to tell GemCad to use the point You shoul
26. d see the message 2pt at the lower left hand corner of your screen If it says 1pt then you forgot to enter the meet point of the main at 64 and the girdle facets about four paragraphs back Now we need to tell GemCad at what index to cut the facet Press the gt Cut Menu key Press the Index i key and enter 2 as the index GemCad should proceed to cut the 16 crown break facets and your display should look like Figure 12 BOTTOM Figure 12 Crown mains and breaks Now we are ready to cut the star facets Press the gt Point Menu key to go to the Point Menu The cursor should still be at the intersection of the main and break facets along the radius of the stone at the 4 index position Press the Meet pt m key to enter the point and press y to use the point Now we shall make two more construction lines We want the line to begin at this meet point so press the key to start the construction line Next move the cursor near the corresponding meet point along the radius at the 52 index position Press the Meet pt m key to snap to the meet point but press Enter to discard the point Again we are only using the Meet pt m key to position the cursor quickly we don t want our star facet at index 4 to meet here Press the key again to draw the construction line Now we shall make another construction line Move the cursor near the meet point of the mains and breaks along the radius at the 60 index position and press the Meet pt m
27. display will look like Figure 37 The crown is now complete The stone might appear too low in the End View so let s move it up a bit Change to the Cut Menu and move your cursor to the location shown in Figure 37 Press the Center c key and GemCad will ask you whether you want to slide the stone along the x y or z axes Enter z and GemCad will scoot the stone up The z axis is the dop axis To use the Center c command you place the cursor inside the stone in the End View at where you want the stone to be centered press the Center c key and enter z If the cursor is below the center of the view GemCad will move the stone upV to make the center of the view at the height on the stone where your cursor was The stone should be positioned as in Figure 38 BOTTOM Figure 38 Now change to the Diagram Menu and let s name label the facets Move the cursor inside one facet and press the Name n key GemCad will highlight the facet and ask you for its name Do this for each facet in turn To name a girdle facet you must be inside the girdle facet in the Side or End View Its name will be shown in the Bottom View however Now press the List to sern 1 key to view the cutting sequence Check to make sure each step has its name in the left column of the listing If you wish you may add cutting instructions for each step with the Gloss inst G key The Heading H key command allows you to enter a heading of up to four lines This is
28. divide the X mouse ticks by two This makes the mouse half as sensitive horizontally as before Similarly the variable myDrIv divides the vertical mouse ticks You can put one or both of these commands in your AUTOEXEC BAT file If you get a DOS error message like Out of environment space you must place the SET commands near the top of your AUTOEXEC BAT file Most of the newer mouse drivers have adjustable resolution and you should fix the problem there
29. e common centerpoint Press the Index i key and enter 96 or zero Press the Angle a key and enter 41 7 Verify that you have a41 7 10 0 displayed in the status box in the lower left hand corner of the screen If so change to the Point Menu Move the cursor back to the centerpoint in the Top View if it is not still there Press the Meet pt m key After you enter tt yto tell GemCad you want to use the point GemCad should cut two more facets at 96 48 and your display should look like Figure 21 TOP SIDE BOTTOM 21 Facets cut to centerpoint for CAM preform Now we are ready to cut the girdle facets at 90 Move the cursor to the location of the crosshairs in Figure 21 Press the Pt on edge e key or the right mouse button and enter y to use the point You should see 1pt in the status box Change to the cut Menu and we will explore a new command Move the mouse cursor inside one of the facets in the Top View and press the Jam index j key You will see the index show up in the status box just as if you had entered the index with the Index i command Try it with several of the facets Now find the facet cut at 24 index and use the Jam index j key to jam its index in the status box You should see lpt i24 0 displayed in the status box Then press the Angle a key and enter 90 GemCad will then cut the two facets at 24 72 Your display should now look like Figure 22 TOP SIDE BOTTOM 22 The length of the p
30. e performance You should see rays similar to Figure 18 All light entering vertically through the mains and stars now exits through the crown TOP SIDE SED I wA An il BOTTOM Figure 18 Paths of light rays after changing the angles Execute the Playback P command in the Utility Menu GemCad will show an animation of the stone The completed stone should look like Figure 19 You can list a cutting schedule to your printer by moving to the Diagram Menu and pressing the List to file L key and entering PRN for the file name The resulting schedule should look like the listing in Table 1 but the angles might be a bit different since their numerical values were not entered but were set by eye BOTTOM Figure 19 The completed brilliant LESSON GEM Angles for R I 1 54 57 facets 16 facets on girdle 73 8 fold mirror image symmetry 64 index L W 1 000 T W 0 583 T L 0 583 P W 0 450 C W 0 108 H W P C W 0 02 0 578 P H 0 778 C H 0 187 Vol W 3 0 190 GIRDLE G 90 00 02 06 10 14 18 22 26 30 34 38 42 46 50 54 58 62 PAVILION M 42 00 64 08 16 24 32 40 48 56 B 43 31 02 06 10 14 18 22 26 30 34 38 42 46 50 54 58 62 CROWN M 27 00 64 08 16 24 32 40 48 56 B 33 08 02 06 10 14 18 22 26 30 34 38 42 46 50 54 58 62 S 15 66 04 12 20 28 36 44 52 60 T 0 00 Table Be sure to save your design with the Save s key This completes the tutorial o
31. e picker GemCad will print a list of all of the files in the current directory whose extension begins with c Subdirectories of the the current directory are also shown The list of subdirectories follows the list of files You can distinguish the two because directory names are followed by the backslash character The directory is the parent of the current directory One of the selections will be in reverse video and will have a small arrow to its left You may use the cursor keys or mouse to change which item is highlighted You make a selection by pressing the Enter key or a mouse button If you select a file name GemCad will try to open the file If you select a directory GemCad will change to the new directory and display all of the files matching the wildcard and all of the subdirectories in the new directory A wildcard is a pattern that matches file names with certain characteristics There is also a special selection labeled file spec This allows you to change disk drives or the wildcard The default drive is the drive where you were when you started the program The default wildcard c matches any file name whose extension starts with c The character matches any one character and the matches an arbitrary string of any length If you get into the file picker by accident you can abort by pressing the Esc key or by selecting empty space This leaves the previous design intact If you select a directory it becomes the
32. erformance of our stone Move the cursor inside the table near the perimeter of the table and press Waytwace w GemCad will trace the ray into the stone and back out The raytrace command is in the Cut Menu Repeat the same for the star and the crown break facets If your screen becomes too cluttered redraw with the Draw d command In particular consider the rays shown in Figure 17 On your screen the portion of the rays inside and outside the stone are shown in different colors Light entering the stars mains and breaks leak out the pavilion Only light entering the table is returned through the crown TOP SIDE BOTTOM Figure 17 Some light rays Now let s lower the angles Move the cursor inside one of the crown mains Press the Blink facet b key located in the Utility Menu The angle of the facet will be shown in the box in the upper left hand corner of your screen and should be 40 Now let s scale the crown to make this angle 27 Make sure the cursor is still inside a crown main and press the Tan ratio T key This command is in the Cut Menu GemCad will tell you what the old angle was and ask you for the new angle Enter 27 GemCad will immediately rescale the crown Next move the cursor inside a pavilion main and change the pavilion mains from 44 to 42 The smaller angles are near those recommended by Long amp Steele and result in a much better performance for quartz Now use the Waytwace w command to check th
33. g angle in degrees of the new facet Pressing the Enter key without entering an angle will abort the command To correct an incorrectly entered angle simply repeat the command and enter the correct angle The new angle will replace the old command Jam angle A Set the angle of a new facet to be the same as that of the facet surrounding the cursor GemCad will search its database of facets and will find the facet surrounding the cursor It will then duplicate the angle as if you had entered it with the Angle a command This can be quite convenient when cutting step cuts with lot of facets cut at the same angle command Index i Set the index of a new facet GemCad will prompt you for the index Indexes may be fractional Pressing the Enter key without entering an index will abort the command To correct an incorrectly entered angle simply repeat the command and enter the correct index See the Index gear g command to find out how to change the number of teeth on the index gear command Jam index j Set the index of a new facet to be the same as that of the facet surrounding the cursor GemCad will search its database of facets and will find the facet surrounding the cursor It will then duplicate the index as if you had entered it with the Index i command This can be quite convenient when cutting step cuts command Change C Change the facet surrounding by the cursor next new facet will replace it The Change C co
34. he Center c key Only the vertical position of the cursor is important The cursor should be above the dot at the center of the End View GemCad will ask which coordinate you want centered Enter z GemCad will redraw the stone sliding the stone down so that the position you specified is at the center of the End View GemCad will slide the stone down the vertical distance from the cursor to the center dot The center command can also be used to shift the center of the dop axis by centering the x or y coordinate in the Top or Bottom Views This is useful for pears and other stones with 1 fold symmetry You will get an error message if the coordinate you specify has its axis perpendicular to the view containing the cursor or if the stone is already centered about the cursor For instance if you tell GemCad to center in the z direction while the cursor is in the Top View GemCad will tell you that you are in the wrong view to center that coordinate since the z axis is perpendicular to the Top View When GemCad cuts a facet it conceptually cuts the stone in two at the plane of the facet and discards one part of the stone and keeps the other How does GemCad know which part to keep and which part to discard The rule is that GemCad keeps the part of the stone containing the point 0 0 0 and discards the other part The 0 0 0 point is marked by a dot at the center of each view If you are cutting a skinny stone such as a marquise and you are hav
35. hor the listing will begin with the heading The relative length width table length and pavilion and crown heights are shown next These dimensions are those called out on the diagram The facets visible in the Top View are labeled Crown and those in the Bottom View are called Pavilion Each tier of facets is given by one or more lines in the listing The tier begins with its name see the Name n command if it has one Next comes the bearing angle in degrees Next come the list of index positions separated by hyphens This might take several lines The rightmost column contains the cutting instructions if you have entered them with the Gloss inst G command If you have used the Footnote F command to enter a footnote the note will be at the bottom of the listing command List to file L List cutting schedule of angles and indexes to printer or file The List to file L command lists the cutting schedule to a file or printer The format is basically the same as with the List to scrn 1 command GemCad will prompt you for the name of the file which must be a valid DOS file name If the file exists GemCad will ask for your permission to write over the file Entering the file name PRN or a port name such as LPT1 or com1 whichever is appropriate on your system will list the cutting schedule to the printer The file that is written is a flat ASCII text file You may use your favorite text editor or word processor to annotate the cu
36. hree points You can specify meet points on the screen with the cursor keys or the mouse GemCad understands radial and mirror image symmetry If you tell it to cut one facet it will automatically cut the other facets on the tier GemCad can scale a stone adjusting the angles for different indexes of refraction GemCad can turn a round design into an elliptical one GemCad can produce formatted listings suitable for use as faceting diagrams GemCad is written in the C programming language and was compiled with Borland s C GemCad runs on an IBM PC or compatible with at least 512KB of memory and VGA EGA Hercules or CGA graphics adapter card The CGA resolution of 640X200 is a bit sparse but is sufficient for many designs An 80x87 numeric co processor is strongly recommended but not required A hard disk is also strongly recommended GemCad supports a Microsoft Mouse or compatible The driver supplied with your mouse such as MOUSE com must be loaded before running GemCad This is most commonly done in the AUTOEXEC BAT file but may be done anytime at the DOS prompt GemCad will not work with a MousE sys device driver such as is loaded in the conf IG sys file To run the program type GEMCAD at the DOS prompt The program will try to detect which kind of graphics adapter card you have but if your screen is messed up try again by typing GEMCAD x where x specifies the graphics adapter and is one of the characters c
37. ill zoom back out to the four views command Undo u Undo the last command that changed the stone The Undo u command undoes the most recent change to the stone Before each change to the stone GemCad saves the stone to disk in a file called gemcad bak in the current directory The undo command simply reads in this file Undo only undoes the previous command repeated undos have no effect If you are running the program off a diskette it must not be write protected If you exit GemCad without saving the changes with the Save s command if forbid the program crashes you have a power failure or if your toddler pushes the red button on your tower system you can get back to one step before the disaster by restarting the program and pressing the Undo u key as the first command The Point Menu The following commands are used to set points that will be used to cut a new tier of facets Whenever you enter one of the point commands GemCad will draw cross hairs intersecting at the point you specified If the command picks a point relating to facets already cut there might be a slight delay while GemCad does the search GemCad will then print the coordinates of the point and ask you if you want to use the point as a piece of information for the cutting of a new tier of facets or discard it Any answer beginning with y will be taken as yes and anything else including just the Enter key will be taken as a no If you are using a mouse the
38. in Figure 5 BOTTOM Figure 5 Defining the extent of the pavilion break facets When you get to the point press the Pt on edge e key GemCad will snap to the nearest edge and ask you whether to use the point If you re satisfied enter y You should see the message 2pt displayed Next go back to the Cut Facets Menu We shall cut our break facets at index positions 2 and following Press Index i key and respond with 2 After GemCad cuts the 16 break facets your screen should look like Figure 6 TOP SIDE BOTTOM Figure 6 After cutting the pavilion break facets Note that you didn t have to tell GemCad at what angle to cut the breaks it figured it out from the index and the two points you entered We have now completed the pavilion and are ready to transfer the stone Press gt Main Menu function key and then go to the Cut Menu by pressing the gt Cut Menu Press the Xfer x key to transfer the stone Your display should look like Figure 7 BOTTOM Figure 7 After transferring the stone It is a good idea to save your work frequently to protect your work from yourself and from power outages This is particularly important when designing a new cut Let s save our work now Press the Main Menu key and then press the File Menu key Press the Save s as key GemCad will ask you Project name GemCad is asking you for the name of the file in which to store the project Enter something like lesson gem If a file by that n
39. ing problems with GemCad cutting a facet in the wrong place cutting away most of your stone GemCad could be cutting off the part you really want it to keep The solution to this problem is to use the center command to slide it up or down so that the center dot is contained in the part you want GemCad to keep command Rotate Tilt r Rotate tilt the stone will prompt for what fraction of a revolution The Rotate Tilt r command will rotate the stone clockwise in the view containing the cursor Thus if the cursor is in the Side or End View the stone will be tilted If the cursor is in the Top or Bottom View the stone will be rotated about the axis of the dop GemCad will prompt you for the numerator and denominator of the fraction of a revolution you want to rotate or tilt the stone Thus if you want to rotate the stone say 10 degrees enter 10 for the numerator and 360 for the denominator To rotate the stone one half revolution enter 1 for the numerator and 2 for the denominator command Tan ratio T Tangent ratio scale top or bottom keying off of facet surrounding cursor The Tan ratio T command is used to change all of the angles of one side of the stone to adapt a design to a different index of refraction GemCad will search its database of facets to find the facet surrounding the cursor The angle of the facet will be printed and GemCad will prompt you for the new angle of this facet The entire side of the stone containing the selec
40. is divided into four views similar to an engineering drawing The Top View is at the upper left the Side View is at the upper right the End View is at the lower left and the Bottom View is at the lower right The index gear is indicated by a circle of numbers in the Top View When GemCad is first run a 64 tooth index gear is used The index positions start at 64 at the bottom of the Top View and increase counterclockwise This rather peculiar orientation was chosen to keep facets cut at small index numbers visible in the Top Side and End Views simultaneously This will make better sense as we cut our first stone You can make the I D position be at the top if you want See the Index gear g key in the reference section at the back of this manual While working through this tutorial be careful not to press the standard alphabetic keys unless responding to questions that GemCad asks Most of the alphabetic keys are shortcuts for commands that we shall learn to execute with the function keys caps Lock should also be turned off the light should not be lit since there are more commands than letters and commands performed by pressing capital letters are generally more dangerous than commands performed with lower case letters What better way to learn than by doing Let s begin with a standard round brilliant in quartz We will use 44 for the pavilion mains and 40 for the crown mains A round brilliant has eight fold mirror image symmetry a
41. key and then press the key labeled Enter You can correct mistakes with the Backspace key any time before pressing Enter Any time GemCad needs a response from you it will prompt you at the top of the screen After you enter the 2 you will notice the message i2 0 in the status box at the lower left hand corner of your screen This portion of the screen contains information about facets about to be cut Now we need to tell GemCad at what angle to cut the facet To do this press the Angle a key GemCad will ask Angle at the top of the screen Enter 90 Press the 9 key the 0 key and then the Enter key You might notice the message a90 00 12 0 appear briefly in the status box at the lower left hand corner of your screen while GemCad cuts the sixteen girdle facets Your screen should look like Figure 2 GemCad knows to cut sixteen facets because it is set for eight fold mirror image symmetry These are the default settings but they may be changed easily GemCad will cut a facet or course of facets as soon as you have given it enough information In this case we specified the index angle For the other facets we will cut later we will also have to specify a cutting depth but for this first tier of facets a reasonable cutting depth is assumed The fundamental rule of GemCad is that it cuts a set of facets as soon as you give it enough information to completely specify one of the facets The four views of the stone are projections
42. key to snap to the meet point and press Enter to discard the point Press the key to start a new construction line Move the cursor near the corresponding meet point along the radius at the 12 index position press the Meet pt m key to snap to the point press Enter to discard the point and then press the key to draw the construction line The two construction lines should intersect on the main facet at the 64 index position Move the cursor to this point of intersection Your display should look like Figure 13 TOP SIDE BOTTOM Figure 13 Establishing the meet point for the star facets We want the star facets to meet the mains at this point Press the Pt on facet f key to set this point and enter y to use it This will drop a perpendicular down until it hits the main facet and set the point of intersection of the perpendicular and the facet You should see the message 2pt at the lower left hand corner of your screen Now we need to tell GemCad to cut the facets at the 4 index position Press the gt Cut Menu key Then press the Index i key and enter 4 Gem will cut the star facets Redraw the stone by pressing the a key to update the dimension lines Your display should now look like Figure 14 TOP SIDE BOTTOM Figure 14 After the star facets are cut Now for the table Press the Angle a key and enter 0 zero Press the gt Point Menu key Your cursor should still be at the meet point of the main at 6
43. l be in outline form Angle a 45 81 Index i 7 Move cursor as shown in Figure 26 BOTTOM Figure 26 Move cursor as shown in Figure 27 Meet pt m and confirm with y Angle a 62 Meet pt m and confirm with y Four facets will be cut at 07 41 55 89 and display will look like Figure 27 BOTTOM Figure 27 Move cursor as shown in Figure 27 Meet pt m and confirm with y Angle a 62 Index i 24 Two facets will be cut at 24 72 Angle a 54 Index i 23 Move cursor as shown in Figure 27 This is same point as used in the last step Meet pt m and confirm with y Four facets will be cut at 23 25 71 73 and your display will look like Figure 28 BOTTOM Figure 28 Move the cursor as shown in Figure 28 Meet pt m and confirm with y Angle a 70 Index i 96 Two facets will be cut at 96 48 Move the cursor to the same point as before Figure 28 Meet pt m and confirm with y Angle a 60 Index i 1 Four facets will be cut at 01 47 49 95 and your display will look like Figure 29 BOTTOM Figure 29 Angle a 42 2 Index i 10 Move cursor as shown in Figure 29 Meet pt m and confirm with y Four facets will be cut at 10 38 58 86 GemCad will warn you that these facets cut off the remaining CAM preform facets Your display will look like Figure 30 BOTTOM Figure 30 Move cursor as shown in Figure 30 Meet pt m and confirm with y Angle a 45 Index i 96 Two facets will be cut a
44. mirror image is the default when GemCad is first run The default can be changed when configuring GemCad The symmetry of the stone is saved when the project is saved with the Save s or Save as S commands You can change the symmetry in the middle of a design For instance you can cut a pavilion with one type of symmetry and a crown with another Only the current symmetry is listed by the List to scrn l or List to file L commands If the number of teeth on the index gear is not an integer multiple of the degree of radial symmetry GemCad will round off indexes to the nearest tooth This allows you for instance to cut a seven sided stone on a 64 index gear command Refr index I Index of refraction change it and print the critical angle The Refr index I command is used to change the index of refraction for the Waytwace w command GemCad will tell you the old index of refraction and will prompt you for the new one GemCad will then print out the critical angle in the upper left hand corner of the display A null response just the Enter key causes the R I to remain unchanged but the critical angle is displayed again When you save a design GemCad saves the R I with the facet data When GemCad is first run the refractive index is set to 1 54 for quartz This default can be changed when you configure GemCad command Time Lapse t Turn time lapse on off The Time Lapse t command affects how the stone is redrawn as facets are
45. mmand has several variations GemCad will ask you Code all top bot x y Zz The scale command has several uses If your response begins with an a or A GemCad will scale the entire stone GemCad will prompt you for the numerator and denominator of the factor by which the stone is to be multiplied The stone is enlarged if the numerator is larger than the denominator or shrunk if the denominator is larger than the numerator No angles or indexes are changed A response beginning with x or x will stretch or shrink the stone horizontally in the Top View You can use this for instance to turn a round design into an elliptical one A response beginning with y or y will stretch the stone vertically in the Top View In either case GemCad will prompt you for the numerator and denominator of the scale factor Angles and indexes will be changed Indexes will probably not be whole numbers the Change C command may be used on each tier to make its index a whole number Facets that used to be at the same index and depth before the scale command might be at different angles and depths after scaling The x or y options will also cause GemCad to re tier the stone This process might take a while on slower machines The re tier operation groups together facets cut at the same bearing angle and depth regardless of their relationship through symmetry To force the re tier operation without otherwise changing the stone scale the stone in the x or y directi
46. mmand is used to recut a tier of facets It is similar in action to killing a tier of facets with the Kill tier K command and then recutting the facet with two exceptions First the index of the old facet is rounded off to the nearest integer and entered just as if you had entered it with the Index i command The index can then be changed to something else with the Index i command Second after the new tier of facets is cut the cutting order remains the same Killing a tier and cutting it again makes the new tier last in the cutting order The change command disables several other commands The auto backup feature is turned off until the facets are recut Thus the Undo u command will get you back to the point just before you executed the change command regardless of any other changes to the stone Only one tier of facets may be changed at a time When a change is pending an asterisk will follow the index printed in the status box in the lower left hand corner of your display If you discard the index with the Draw d command GemCad will print the previous index in parentheses in the status box A problem can arise if you are cutting a design that has mixed symmetry that is some tiers of facets are cut with one type of symmetry and others are cut with another type of symmetry GemCad does not keep track of which facets were cut with which symmetry setting So if you use the Change C command to change a tier of facets make sure yo
47. n on the distance from the top of the page regardless of the length of the header The four parameters that you can set are Top margin The number of blank lines from the top of the listing to the first line of the header Left margin The number of spaces before each line of the cutting instructions Top header The maximum number of lines in the header or the number of lines from the top margin to the beginning of the cutting instructions Left header The extra number of spaces that the header is indented If you set these four parameters to zero the format of the List to file L command will be identical to the format of the List to scrn 1 command The default choices for these were tested with the GemDot prorgram with Epson LQ510 printer using its Courier typeface You will have to experiment with the margins to adapt the listing format to your printer GemCad can print a copy of the screen on HP DeskJet LaserJet or IBM or Epson printers All of the HP printers need the information in one format and the IBM and Epson printers need it in another If you select the IBM compatible printer GemCad will ask you for the aspect ratio of your printer For most 9 pin printers enter 1 2 For most 24 pin printers enter 1 GemCad will print only the square plotting area of the screen Make a test plot with one of the suggested values above and measure the square to make sure its width is the same as its height If not reconfigure GemCad
48. n the round brilliant GemCad Tutorial Lesson 4 78 18 72 24 CSE rans a g A Form e Cross Rectangle FORMEE_R GEM by Robert W Strickland Revised 7 28 91 5 10 92 5 8 93 Angles for R I 1 54 67 facets 8 facets on girdle 75 2 fold mirror image symmetry 96 index LIW 1 272 T W 0 795 T L 0 625 P W 0 649 C W 0 240 H W P C W 0 02 0 909 P H 0 714 C H 0 264 Vol W43 0 526 CAM PREFORM PF1 33 40 10 38 58 86 Cut to TCP PF2 35 00 24 72 Cut to TCP PF3 41 70 96 48 Cut to TCP G1 90 00 24 72 Cut to final length G2 90 00 10 38 58 86 Level false girdle G3 90 00 96 48 evel false girdle PAVILION 1 43 00 13 35 61 83 Cut to TCP of preform 2 46 00 10 38 58 86 Meet G1 G2 1 3 45 81 07 41 55 89 Meet G2 G3 2 4 62 00 24 72 Level girdle 5 54 00 23 25 71 73 Meet 2 4 at girdle line 6 70 00 96 48 Meet 2 3 at girdle line 7 60 00 01 47 49 95 8 42 20 10 38 58 86 Meet 1 2 3 9 45 00 96 48 Meet 8 at culet 10 47 31 03 45 51 93 Adjust angle if needed CROWN A 51 00 24 72 Leave some girdle B 42 50 23 25 71 73 t girdle line C 35 00 19 29 67 77 i D 44 00 10 38 58 86 Level girdle E 39 40 03 45 51 93 t girdle line F 42 19 02 46 50 94 y G 61 00 96 48 Level girdle H BEIA 07541 55 89 t girdle line J 35 82 14 34 62 82 T 0 00 Table Table In this lesson we will cut a rectangular design called the F
49. nd can be cut on a 64 index gear These are the default settings when GemCad is first run You can change the symmetry with the Symmetry y command described in the reference section of this manual We shall begin by cutting girdle facets at 90 to preform the stone At the left of your display you will notice the title MAIN MENU and several lines beginning with F1 F6 that correspond to the function keys on your keyboard The function keys will be along the left or top of your keyboard depending on the model In the Main Menu all of the labels begin with the gt character indicating that selecting the corresponding function key will move to a different menu Now experiment with moving around in the menu structure by pressing the function keys corresponding to labels starting with gt If you are using a mouse you can also point at one of the function key legends to cause it to light up Then press any mouse button to execute the highlighted choice You will notice single alphabetic characters to the right of function key labels These are abbreviations for the corresponding function key commands Typing the alphabetic key is equivalent to pressing the corresponding function key So what s the shortcut if either takes but a single keystroke The advantage is that you don t have to be in any particular menu to execute a command with an alphabetic key This saves you the trouble of wandering through the menu hierarchy if you already know the command
50. new working directory command Save s Save the project as a binary file with the existing project name The Save s command saves the design to disk as a binary file If the project doesn t yet have a name GemCad will ask you for one The name must be a valid DOS file name eight or fewer characters and an optional three character extension If you don t provide an extension GemCad will automatically add ce to the end If you don t want an extension end the file name with a period Note that an extension beginning with G will make the file picker much easier to use The binary file is not readable by a human you ll get hearts and clovers and all sorts of stuff if you type it but can be read quickly by GemCad If the file you specify already exists GemCad will ask your permission to write over the file command Save s asSave the project as a binary file with a new project name The Save as S command is similar to the Save s command except that GemCad will prompt you for a file name even if the project already has a name command New N Begin a new cut TRASHES EXISTING PROJECT The New N command is used to start over from scratch This command deletes all facets GemCad will ask your permission to trash the existing design before it does so command Read R Read a project from a text file such as made by the W command The Read R command reads the project from an ASCII text file such as made by the Write te
51. on by a factor of 1 over 1 After the stone is re tiered GemCad will prompt you for the new symmetry of the stone just as if you had entered the Symmetry y command This new symmetry applies only to facets yet to be cut If your response begins with a t or T GemCad will scale the side of the stone currently in the Top View be it the pavilion or crown If your answer begins with a b or B GemCad will scale the side of the stone in the Bottom View A response beginning with z or z will stretch or shrink the stone vertically in the End View thus scaling both the pavilion and crown by the same factor All three variations perform Tangent Ratio scaling In most cases however the Tan ratio T command is easier to use GemCad will prompt you for an old angle and a new angle GemCad will scale the stone such that a facet which was formerly at the old angle will be at the new angle This will change the angles but not the indexes If your stone does not have a level girdle the girdle line might be distorted somewhat after the stone is scaled This can be fixed with the Playback P command The Undo u command is also duplicated in the Cut Menu It is described in the section on the Cut Facets Menu above The Parameter Menu The commands in the Parameter Menu are used to set parameters or switches command Index gear g Change the index gear The Index gear g command is used to change the number of teeth of the index gear GemCad defaults to a
52. orm e Cross Rectangle For this design we will need a Centerpoint Angle Method CAM preform Briefly this technique allows you to reproduce the girdle outline of the design without having to make any measurements One cuts several facets to a common centerpoint a meet point on the dop axis This set of facets will be cut off later by the actual pavilion facets One then cuts facets at 90 making a level false girdle line and establishing the outline of the stone Run GemCad Change to the Parameter Menu and press the Index gear g key and set the index gear to 96 GemCad will ask you for the number of teeth and the bottom index position Enter 96 for the number of teeth and 0 for the offset This will make the 96 position at the bottom of the circle of numbers in the Top View Next change the symmetry to two fold mirror image with the Symmetry y command Enter 2 and y in response to GemCad s questions about the symmetry Now we are ready to cut the first four facets Change to the Point Menu and use the Query user q command GemCad will ask you for the coordinates of the point Enter 0 0 1 for the x y and z coordinates respectively Enter y to tell GemCad you want to use the point You will see 1pt displayed in the status box Recall that if you make a mistake and the information in the status box is incorrect you can clear it with the Draw d key in either the Cut Facets Menu or Point Menu Next change to the the Cut Facets Menu and p
53. owever command Print Screen F12 Print what s on the screen Function key F12 performs a screen dump If your keyboard does not have F12 or it doesn t work you may use Shift F2 instead This command shows up in every menu This print screen function is completely independent of ordinary keyboard key labeled Print Scrn that invokes the DOS print screen function so it is not necessary to load the GRAPHICS com program for the F12 screen dump to work GemCad supports IBM compatible dot matrix printers and Hewlett Packard LaserJet and DeskJet printers See the configuration section of this manual to find out how to specify the printer type command Crosshairs Spacebar The spacebar draws or erases the dotted crosshairs across the screen that intersect at the cursor The crosshairs Spacebar command doesn t show up in any menu but is always available The crosshairs are convenient for lining things up vertically or horizontally It also serves to tack down the cursor if you use the mouse to pick items from the menu bar If the command you plan to use requires a point you can tack down the cursor with the spacebar Then when you select the item from the menu bar GemCad uses the location of the crosshairs and does not ask you to set a point The Cut Facets Menu The commands in this menu are for cutting new facets The basic philosophy behind the cutting of new facets is that GemCad will cut a tier of facets as soon as you have given it eno
54. p S export E command makes a disk file compatible with the programs written by Robert Long and Norman Steele GemCad will prompt you for the name of the data file The name you enter should end with the P3D c3D or B3D extension depending on whether your design is just a pavilion just a crown or both pavilion and crown respectively If you don t supply an extension GemCad will add 83D to the name There are several caveats to this translation process The names of facets and the refractive index will be lost and the cutting order will be changed to make the crown first in the data file The orientation of the index gear will be changed to I D position at the top since that is the orientation that the Long amp Steele programs expect but the direction of indexing will be preserved The z 0 plane will be made to coincide with the girdle line This command might take a long time on machines without numeric co processors command Quit Q Quit GemCad The Quit Q command is used to exit GemCad You can also use the Esc key to quit If you have not saved the current design since making a change or addition GemCad will ask you if it is OK to quit anyway command Help h Print out help for next command instead of doing next command The Help h command shows up in every menu The Help h command prints out a one or two line description of the next key that you press The command corresponding to the key you press is not executed h
55. radial symmetry can be cut at once The exceptions are facets that are mirrored by themselves facets whose indexes are integer multiples of the number of teeth on the gear divided by twice the degree of radial symmetry Consider an example A standard round brilliant has eight fold radial and mirror image symmetry If enough information is given to cut one of the break facets GemCad will cut all sixteen break facets at once It knows however to cut only eight mains and stars because these facets are mirrored by themselves What about other symmetries If the stone is put at the center of a pie the degree of radial symmetry is the maximum number of identical wedge shaped pieces into which the stone can be cut If it can t be cut into at least two pieces the degree of radial symmetry is one If each of the identical pieces has bilateral symmetry if it can be folded in two along its centerline then the stone also has mirror image symmetry Consider some examples A snowflake has six fold mirror image symmetry It can be cut into six identical pieces and each of the six pieces can be folded in two A pear shaped stone has no radial symmetry but has mirror image symmetry so it has one fold mirror image symmetry A stone whose outline is a parallelogram has two fold radial symmetry but does not have mirror image symmetry An emerald cut has two fold mirror image symmetry Most triangular stones have three fold mirror image symmetry Eight fold
56. reform is now established Now move the cursor inside the facet at index 10 Use the Jam index j command to grab its index Keep trying until GemCad displays 110 0 in the status box Now move the cursor inside the big facet at 90 in the Side View Use the Jam angle A command to grab its angle You should see a90 0 i10 0 displayed in the status box Now change to the Point Menu move your cursor to the point in the Side View as indicated in Figure 22 Press the Meet pt m key or left mouse button to pick the meet point and enter y to tell GemCad to use the point GemCad will then cut the four facets at 10 38 58 86 and your display should look like Figure 23 BOTTOM 23 Corners cut off Move the cursor to the point in the End View indicated by the crosshairs in Figure 23 Press the Meet pt m key or left mouse button to pick the meet point and enter y to use the point Change to the Cut Facets Menu and move the cursor inside the facet at the 96 index position Just a bit up and to the left of the position in Figure 23 Use the Jam index j command to grab its index You should see 1pt i0 0 in the status box Recall that index position 0 is the same as 96 Now move the cursor inside the girdle facet at the 10 index position just below the position in Figure 23 Use the Jam angle A command to jam in its angle of 90 and GemCad will cut the final two girdle facets at 96 48 This completes the CAM preform Your display sho
57. ress the Index i key Enter 10 Now press the Angle a key and enter 33 4 GemCad will then cut four facets at index positions 10 38 58 86 and your display should look like Figure 20 TOP SIDE BOTTOM 20 The start of the CAM preform For many cuts you can just enter the angle and index of the first set of facets and GemCad will assume a reasonable cutting depth Here we typed in the coordinates of the centerpoint Note also that it was necessary to enter this centerpoint before the angle and index For some designs with high angle facets about 50 or higher the center point will be off the screen and instead of a centerpoint you will see what looks like a facet at the top of the stone GemCad starts off with a cube of rough a bit smaller than each view The faces of this cube are not drawn but all facets cut will be truncated at the faces of the cube The four facets meet at the exact center of the Top View This is the centerpoint to which the other facets of the preform will be cut Now change to the Point Menu Move your cursor near the centerpoint as shown by the crosshairs in Figure 20 Press the Meet pt m key or the left mouse button and enter y to tell GemCad you want to use the point Now change to the Cut Facets Menu press the Angle a key and enter 35 Then press the Index i key and enter 24 GemCad will then cut two facets at 24 72 making a total of 6 facets Now let s cut the last pair of facets cut to th
58. s since all the commands are available all the time If you type reasonably well the alphabetic keys might be easier to locate than the function keys Remember to be sure that caps LOCK is off the light is not lit since upper case commands are different from and generally more dangerous than lower case commands The help key is F11 or Shift F1 in every menu If you press the Help h key followed by another function key GemCad will print a one sentence description of what the key does This tells what the key does when it is not preceded by the Help h key You should have received a sheet of paper listing all of the menus A file called MENUS TXT contains the same information Use this for a road map as you explore the menus After you have explored the menus get back to the Main Menu by pressing the gt Main Menu function key TOP SIDE BOTTOM Figure 2 Girdle facets Cutting is done while in the menu called Cut Facets Menu To get to the Cut Facets Menu from the Main Menu press the gt Cut Menu key We shall begin by cutting 16 girdle facets at 90 to preform the stone GemCad can handle only faceted or knife edge girdles it cannot handle a round girdle Using a 64 index the girdle facets are at indexes 2 6 10 To tell GemCad to cut at index position 2 use the Index i key You will see the question Index appear at the top of your screen in dark letters on a white background Enter 2 That is press the 2
59. sions 2 0 and later of GemCad support a Microsoft or compatible mouse most are The interface program supplied with your mouse such as Mouse com must be loaded before running GemCad This is most commonly done in the AUTOEXEC BAT file but may be done anytime at the DOS prompt GemCad does not work with device drivers such as mouse sys that are loaded in the conf IG sys file You can use the mouse to position the cursor and to execute commands If you move the mouse pointer into the menu label area at the left of the screen you can highlight a particular menu choice Pressing any of the mouse buttons while a choice is highlighted will select that choice This is equivalent to pressing the corresponding function key with one exception if the command you selected refers to a point GemCad will print Set a point in the upper left hand corner of the screen The selected menu choice will then remain lit until you move the cursor into the drawing area position the cursor at the point you want and then press a mouse button The command will then be executed just as if you had pressed the corresponding function key while the cursor was at the point you set When the cursor is positioned in the drawing area and a menu choice is not highlighted the mouse buttons are mapped to commands in the Point Menu The left button is mapped to the Meet pt m command and the right button is mapped to the Pt on edge e command If you have
60. st to file L commands to the right of the indexes that make up the tier command Heading H Enter a heading including title designer date etc The Heading H command allows you to enter up to four lines of text that show up at the top of the listing with the List to scrn l or List to file L commands If you have already used the Heading H command to enter a heading subsequent times allow you to edit the heading You may use the Insert Delete End and Home keys The purpose of this text is to allow you to enter the name of the design the designer the date and reference command Footnote F Enter a footnote The Footnote F command allows you to enter up to four lines of text that are printed at the bottom of the listing made with the List to sern l or List to file L commands If you have already used the Footnote F command to enter a footnote subsequent times allow you to edit the footnote You may use the Insert Delete End and Home keys Configuring GemCad When you first run GemCad it will print out a Copyright notice tell you where it got its current configuration and ask you press c to configure or any other key to start the program If you press the c or c key GemCad will enter its configuration mode This allows you to change the default parameters such as index gear and symmetry It also allows you to specify parameters relating to your printer This configuration is stored in a file named GemcaD cF
61. stance In most cases you will probably want to set this distance as one unit long command Playback P Recut the stone The Playback P command is used to recut the stone The stone is shown at every stage as it is recut GemCad will ask you if you want it to wait for you to press a key between facets If your answer begins with a y GemCad will cut facets one at a time waiting for you to press any key or mouse button Otherwise GemCad will ask you how long to wait between facets A value of 0 5 seconds slows things down enough to see each facet as it is cut The default is not to wait at all Since the playback can take a long time on machines without numeric co processors pressing the Esc key will abort the playback The overall effect of the playback is to show an animation of the stone as it is cut The playback command also recomputes the stone and can sometimes improve the appearance of meet points or edges You should use the Playback P command after the Tan ratio T command to improve the accuracy of the computed meet points command Demo D Recut the stone repeatedly to demonstrate GemCad The Demo D command repeatedly executes the Playback P command in an endless loop As with the Playback P command GemCad will ask you how long to pause between facets After the stone is recut GemCad will pause for five seconds The demo will continue until you interrupt it with the Esc key command Constr line First time
62. starts at cursor second time draws to cursor The first time you press the Constr line key GemCad does nothing except to save the last location of the dotted cross hairs or the cursor if the cross hairs are not on The second time you press the minus key GemCad will draw a dotted construction line from the saved point to the new location of the crosshairs or cursor You can get crosshairs at the cursor by pressing the space bar command Dos Execute a DOS command The Dos command allows you to executes one or more DOS commands GemCad will prompt you with Dos gt at the top of the screen and you may enter a one line DOS command which will be executed in a text screen After DOS executes the command GemCad will ask you to press any key to redraw the stone If you want to escape to a DOS session to execute several commands and then return to GemCad simply press the Enterg at GemCad s Dos gt prompt This will start new DOS session in a text screen When you finish the DOS session you must use the ExIT command of DOS to return to GemCad The Diagram Menu command List to sern 1 List cutting schedule of angles and indexes to screen The List to sern 1 command lists the cutting schedule to the screen Facets are listed in the order they were cut GemCad will wait for you to press any key or mouse button at the bottom of each full screen of text If you have used the Heading H command to enter the design name and aut
63. t 96 48 and your display will look like Figure 31 Angle a 47 31 Index i 3 Move cursor as shown in Figure 31 BOTTOM Figure 31 Meet pt m and confirm with y Four facets will be cut at 03 45 51 93 This completes the pavilion Change to the Cut Menu and press the Xfer x key to transfer the stone Your display should look like Figure 32 VAN Ore Mea BOTTOM Figure 32 Now we need to establish the thickness of the girdle Move the cursor to the point shown in Figure 32 The cursor should be on the horizontal line in the Side View a bit to the left of the girdle line Press the Pt on edge e key or the right mouse button and confirm with y There should now be a vertical dotted line in the Side View and this line should define the girdle thickness If the girdle thickness is not correct redraw with the Draw d key and set the point again Angle a 51 Index i 24 Two facets will be cut at 24 72 and your display should look like Figure 33 SZ VAN ae Ea h BOTTOM Figure 33 Angle a 42 5 Index i 23 Move the cursor as shown in Figure 33 This meet point will be used for the next 3 steps as well Meet pt m and confirm with y Four facets will be cut at 23 25 71 73 Move the cursor back to the point shown in Figure 33 if it is not already there Meet pt m and confirm with y Angle a 35 Index i 19 Four facets will be cut at 19 29 67 77 Angle a 44 Index i 10 Move
64. ted facet will be scaled by the ratio of the tangents of the two angles If the stone does not have a level girdle the junction of the pavilion and crown might be distorted If this is the case the Playback P command can be used to recompute all facet edges and make the facets meet properly command Waytwace w Trace a light ray from cursor into stone and back out of stone The Waytwace w command twaces a single way ahem traces a single ray of light through the stone This is the only command in the Cut Menu that does not change the stone It was placed in the Cut Menu to be close to the Tan ratio T command The light ray will enter the screen perpendicular to the cursor bounce around in the stone and then exit the stone The ray is shown in all four views This is a single shot sort of a deal one ray of light per command A separate program see the READ ME file on your GemCad distribution diskette is used to make ray traced images of your design You can note the leaky spots in the design and use the Waytwace w command to find out the cause of the leak The Refr index I command is used to change the index of refraction Rays are drawn in complement mode shooting an identical ray a second time will erase it A good ray should enter and exit crown facets command Scale X Scale the stone change angles shrink enlarge stretch etc The Scale X command is used to stretch or shrink the stone in one direction The co
65. the Save s as command and specified a project name and the status message Saved has been printed in the upper left hand corner of your screen it s safe to exit the program This done with the Quit Q selection in the File Menu GemCad Tutorial Lesson 2 Welcome back In this lesson we shall cut the crown of our round brilliant Run the GemCad program Press the File Menu key to get to the File Menu Now we need to open the project Press the Open O key to reopen the project GemCad will ask you for the name of the project file Here you could type in the name of the project but just respond by pressing the Enter key and GemCad will activate a file picker This allows you to open projects by clicking on their names with the mouse or by selecting them with the cursor keys You should see the name of the current directory printed at the top of your display You should see the entry labeled file spec at the top of the column of files You should also see the name of your file and perhaps other GemCad files If you don t see your file name one of two things could have happened If you didn t gave your file name an extension that doesn t begin with c the file will not be matched by the wildcard If this is the case click on file spec and change the wildcard to Now all of the files in the current directory will be visible including your project file If not you are probably not in the same directory as you were when you saved the file at the
66. the cursor back to the point shown in Figure 33 if it is not already there Meet pt m and confirm with y Four facets will be cut at 10 38 58 86 and your display will look like Figure 34 BOTTOM Figure 34 Move cursor as shown in Figure 34 Meet pt m and confirm with y Angle a 39 4 Index i 3 Four facets will be cut at 03 45 51 93 Angle a 42 19 Index i 2 Move the cursor back to the point shown in Figure 34 if it is not already there Meet pt m and confirm with y Four facets will be cut at 02 46 50 94 Move the cursor back to the point shown in Figure 34 if it is not already there Meet pt m and confirm with y Angle a 61 Index i 96 Two facets will be cut at 96 48 Angle a 38 31 Index i 7 Move the cursor back to the point shown in Figure 34 if it is not already there Meet pt m and confirm with y Four facets will be cut at 07 41 55 89 and your display should look like Figure 35 Figure 35 Move the cursor to the location indicated by Figure 35 If you don t see it look again it s in the Side View near the girdle line Meet pt m and confirm with y Angle a 35 82 Index i 14 Four facets will be cut at 14 34 62 82 and your display will look like Figure 36 Now we are ready to cut the table AN m Angle a 0 There is no need to specify an index for the table ve the cursor to the locati VAN Pee a BOTTOM Figure 37 GemCad will cut the table and your
67. the point Only one of the x y z coordinates depends on the screen resolution the other two depend on the equations of the two facets that form the edge When the cursor is visible the right mouse button is equivalent to the Pt on edge e command command Pt on facet f Set a point of a new facet on the interior of an old facet at cursor GemCad will search its database of facets and determine which facet surrounds the cursor GemCad will then project the line of sight through the cursor and calculate the point of intersection of this line and the facet GemCad will print the x y z coordinates of the point and ask you if you want to use the point Since GemCad determines two of the three coordinates from the cursor position the resolution of this command is limited to that of your particular display Even with CGA resolution however this is seldom a serious limitation unless cutting designs with small floating facets When the cursor is visible the center button on a three button mouse or pressing both buttons of a two button mouse are equivalent to the Pt on facet f command command Z axis inept Z Set a point where the plane of the facet surrounding the cursor intersects the z dop axis This command is useful if you are cutting several facets to a common centerpoint It s also an easy way to cut two facets at the same angle and mast height Place the cursor inside an existing facet If the facet encloses the centerpoint of the Top
68. tting instructions and print them out The format of the List to file L command is somewhat different than that of the List to sern l command The heading and dimensions are set off in an indented block by themselves The cutting instructions follow When you configure GemCad you can specify the margins the height of the header and how much the header is indented command Name n Name or label the facet surrounding the cursor The Name n command searches the database of facets to find the facet surrounding the cursor GemCad then prompts you for the name of the facet and labels the facet with the name Names can be up to three characters although only one or two character names will fit in any but the largest facets The names will also appear in the cutting schedule made by the List to sern 1 and List to file L commands Naming a facet that already has a name renames the facet but a null name just the Enter key will erase the name If two facets in the same tier of facets same angle and depth are named different names only one name will appear in the cutting schedule command Gloss inst G Provide cutting instructions for facet surrounding the cursor A gloss is a brief explanation or annotation The Gloss inst G command allows you to provide brief cutting instructions for a tier of facets one of which surrounds the cursor The cutting instructions will be printed on the listing made with the List to sern l or Li
69. u set the symmetry properly for the changed tier command Draw d Draw the stone again discard set points The Draw d command is used to redraw the stone As you cut new facets GemCad only redraws the facets that change Sometimes in the process of redrawing facet labels see the Name n command and index labels can become partially erased Redrawing the stone cleans up the display The Draw d g command also discards any pending information about facets to be cut angle index or points and clears the status box in the lower left hand corner of the screen Thus the Draw d command is also useful for correcting input errors The Draw d command also places dimension lines on the drawing of the stone Each dimension is given by a single character L W P C or T corresponding to the length width pavilion crown and table The relative values of these dimensions are listed with the List to sern l or List to file L commands If a facet is changed or a new facet is cut that changes the dimensions of the outline or table the dimension lines will not be updated on the screen until the Draw d command is executed command Zoom z Zoom in on the view surrounding the cursor or zoom back out again The Zoom z command enlarges the view containing the cursor to fill the entire screen The zoom command toggles between two magnifications the command doesn t do arbitrary magnifications If one view fills the screen the zoom command w
70. ugh information to specify one of the facets of a tier Facets on the same tier are cut at the same angle and depth and have indexes related to each other through the symmetry of the stone The section on the Symmetry y command gives more information on symmetry To determine the plane of a new facet GemCad needs three pieces of information There are several different combinations of three pieces of information that will determine the plane of a new facet One point the index and the angle Two points and the index Two points and an angle of 90 Three points The commands in this section allow you to give GemCad the angle or index of a facet to be cut GemCad will cut the facet immediately after you give it the last piece of information needed to specify the facet Sometimes you might not recall what information you have already specified The status box in the lower left hand corner of the screen shows a summary of the information GemCad has for new facets There are fields for the angle index and the number of points entered so far If you have not given GemCad any information about a new facet GemCad will display in the box the number of facets cut so far To correct information in this field the Draw d command will redraw the stone and clear this field and cause any pending information about new facets to be discarded command Angle a Set the angle of a new facet GemCad will prompt you at the top of the screen for the bearin
71. uld now look like Figure 24 BOTTOM 24 The completed CAM preform Next we will cut the actual pavilion facets These will cut off the preform facets that meet at the centerpoint Now we shall cut facets at index positions 13 35 61 83 Press the Index i key and enter 13 Press the Angle a key and enter 43 You should now see tt a43 0 i13 0in the status box Change to the Point Menu and move the cursor to the centerpoint as shown in Figure 24 Press the Meet pt m key or the left mouse button and enter y to use the point GemCad will cut 4 facets and tell you that 6 facets were cut off You must press any key to acknowledge this warning The 4 new facets cut off 6 of the CAM preform facets and we will lose the other 2 later Your display should look like Figure 25 TOP SIDE 48 54 42 60 36 BOTTOM 25 First four pavilion facets Move the cursor to the location in the Side View shown in Figure 25 Press the Meet pt m key or left mouse button to enter the meetpoint and press enter y to confirm Change to the Cut Facets Menu and enter an angle of 46 and an index of 10 GemCad will cut the four facets at 10 38 58 86 Your display should look like Figure 26 From now on I ll assume you are now sufficiently familiar with changing back and forth between the Cut Facets Menu and the Point Menu and know how to use the Meet pt m key command the Index i key command and the Angle a key command The remaining instructions wil
72. xt W command If facets have been cut already GemCad will ask you for permission to trash them This command can be slow if your machine doesn t have a a numeric co processor See the Write text W command for details about the file format command Write text W Write the project as a text file The Write text W command is used to write the project as an ASCII text file GemCad will prompt you for the name of the ASCII file If you don t supply an extension GemCad will add ASC to the name The Write text W command makes a file that is free format The ASCII files have two main uses The first is to archive designs The ASCII files have no information about the vertices that make up the facets but only have information about the plane of each facet This means that the ASCII format is very compact The other main use is to extend or subvert the capabilities of GemCad You can edit the resulting file with a text editor or word processor make changes and then read it back in again with the Read R command You can use this technique to combine the pavilion and crown from separate files The text file has one line per tier of facets unless there are more than 16 facets on one tier With a text editor you can interchange lines to alter the cutting order A text editor is a program that allows you to make changes to text files Text editors differ from word processors in that they don t add any formatting information to the file The ED

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