Modeling the Chess Set

1. Chessboard

In this lesson, we are going to model the chessboard. Given below is our target design:

09 chessboard

Create a new database name chess.g

opendb chess.g ENTER

2. Assigning a title to your database

In the MGED command window, type title followed by the title of your database justifying what you are making. Press Enter at the end.

mged> title Chess ENTER

3. Creating a single tile for the chessboard

Before beginning, make sure that MGED Command Window is active (by clicking anywhere in the window). Then type in the command:

in tile.s1 rpp 0 1 0 1 -0.1 0

47 tile

4. Making a region of the tile

Type in the MGED prompt:

r tile.r1 u tile.s1

This command makes a region with the name tile.r1

5. Understanding the clone command

Let’s understand the clone command first. This command is used to do deep copying in MGED. The syntax for this command is:

clone [-abhimnprtv] <object>

Here each one of the [-abhimnprtv] have a specific meaning to it. Let’s better understand this command using examples.

Create a demo database by typing mged demo.g in the command prompt. Then, create a sphere using the in command as follows:

in tile.s1 rpp 0 1 0 1 -0.1 0 ENTER

Option -a <n> <x> <y> <z> specifies the translation split dimensions between n clones. Type,

clone -a 2 0 0 3 tile. ENTER

MGED will show this:

tile.s101 {tile.s101 tile.s201}

This means, you have got two clones separated by distance 3 units on the z-axis. To visually verify it, type:

draw tile.s101 tile.s2 ENTER

48 tile translation clones

Option -b <n> <x> <y> <z> specifies a rotation around the x, y and z axes split between n copies.

Example: Type Z on the MGED command prompt to clear the graphic window. Then type,

mged> draw tile.s1
mged> clone -b 2 0 180 0 tile.s1
tile.s301 {tile.301 tile.401}
49 tile rotation clones

You see that the cloned tiles are separated from each other by an angle of 180 along the y axis.

  • -c — Increment the second number in object names.

  • -f — Don’t draw the new object.

  • -g — Don’t resize the view after drawing new objects.

  • -h — Prints the message.

  • -i <n> — Specifies the increment between each copy.

  • -m <axis> <pos> — Specifies the axis and point to mirror the group.

  • -n <# copies> — Specifies the copies you make.

  • -p <x> <y> <z> — Specifies point to rotate around for -r. Default is 0 0 0.

  • -r <x> <y> <z> — Specifies the rotation around x, y and z axes. It works same as -b when combined with -n.

  • -t <x> <y> <z> — Specifies the translation between each copy. It works same as -a when combined with n.

  • -v — Prints version info.

6. Cloning the tile for three other tiles

Coming back to our chessboard, let’s clone the tile we made earlier. Now, type:

clone -t 2 0 0 -i 1 -n 3 tile.r1 ENTER

MGED will respond with:

tile.r2 {tile.s2 tile.s3 tile.s4 tile.r2 tile.r3 tile.r4}

This command translates the first clone tile.r2 at x:2 y:0 z:0 (leaving a gap of 1 unit) and then increments it value by 1 for the next clone. -n 3 specifies that it creates three clones (tile.r2 tile.r3 tile.r4)

This command successfully creates single colored tiles of a row. Till now, you can only see one tile in the graphics window, to see all the clone, type:

draw tile.r2 tile.r3 tile.r4 ENTER

Left click on the graphic window for all the tiles to fit in the graphics window.

50 tiles of a row

7. Grouping the tiles in a row

Let’s group these tiles in one row:

g row.g1 tile.r1 tile.r2 tile.r3 tile.r4 ENTER

8. Creating an alternate row by cloning

To get the tiles in alternate position as present in the above screenshot, we will clone this row and translate it to x:1 y:1 z:0, as shown below:

clone -t 1 1 0 -i 1 row.g1 ENTER

MGED will respond with:

row.g2 {tile.s5 tile.r5 tile.s6 tile.r6 tile.s7 tile.r7
tile.s8 tile.r8 row.g2}

Type draw row.g2 ENTER in the command prompt to view the row.g2:

51 two rows of tiles

There are total 8 rows in a chess board, so we will have 3 clones each of row.g1 and row.g2

9. Making the remaining rows

Now, we will be translating along the y axis, therefore the command will be:

clone -t 0 2 0 -i 1 -n 3 row.g1 ENTER

And for row.g2

clone -t 0 2 0 -i 1 -n 3 row.g2 ENTER

You will get row.g3 , row.g4 , row.g5 clones of row.g1 and clones row.g6 , row.g7 , row.g8 of row.g2.

You can view these rows by using the draw command:

draw row.g3 row.g4 row.g5 row.g6 row.g7 row.g8 ENTER

52 all alternate tiles

You see that here we only have alternate tiles i.e., tiles of one color. Let’s group them together under one name black.g as shown below:

g black.g row.g1 row.g2 row.g3 row.g4 row.g5 row.g6 row.g7 row.g8 ENTER

Now, in order to make the white tiles we will clone the group of black tiles black.g , as shown below:

clone -r 0 0 90 -p 4 4 0 black.g ENTER

We will get a clone with the name black.g2. We can change the name of this group to white.g using the mv command.

mv black.g2 white.g ENTER

Now, let’s have a look at the rest of our slides by typing draw white.g

53 all tiles

10. Giving colors to our tiles

In this section we will color our tiles using the comb_color command which means combination color i.e. color of the whole combination/group. The syntax to use this command is:

comb_color combination R G B

Where combination is the name of the combination we want to color. R, G and B are the red, green and blue values respectively.

To color the black tiles:

comb_color black.g 0 0 0 ENTER

To color the white tiles:

comb_color white.g 255 255 255 ENTER

Now combine these black and white tiles to form a board.

g board.g black.g white.g ENTER

And then comes the final part, which is to raytrace our chessboard. Before we raytrace, move the mouse pointer to the Command Prompt and type at the prompt:

B board.g ENTER

This command clears the screen and redraws the board with the specified colors.

11. Raytracing the Board

Go to the File menu and select Raytrace. The Raytrace Control Panel opens. To have a lighter background, click on the dropdown button on the right of Background Color. Click on Raytrace to start the raytracing process.

54 raytrace control panel

While it is raytracing, click on the Framebuffer options in the Raytrace Control Panel Menu Bar and click on Overlay.

After the raytracing process is completed, you get a board, as shown below:

55 chessboard