Modeling the Chess Set

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

Create a new database name chess.g

opendb chess.g ENTER

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

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

Type in the MGED prompt:

r tile.r1 u tile.s1

This command makes a region with the name tile.r1

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:

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

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,

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

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:

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.

Let’s group these tiles in one row:

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

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:

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

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

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

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

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.

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.

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: