Modeling Pawn

10 pawn

Let’s begin by creating a new database for your pawn and name it pawn.g. As discussed earlier, to create a new database type the following command in the Command Window:

opendb pawn.g ENTER

1. Creating a cylinder for the base

Begin by making the Command Window active (usually by clicking anywhere in the window). To make the right circular cylinder, type the following command in the MGED prompt:

in base.rcc rcc ENTER

Here, in is the command which is used to INsert a primitive shape, base.rcc is the name of the shape and rcc means it is a Right Circular Cylinder.

MGED asks you to enter x, y and z values of the vertex (where you want to place the center of the bottom of the shape). Type:

0 0 0 ENTER

Make sure to add spaces between the values.

Next, MGED will ask you to enter the x, y and z values of the height (H) vector (the height of your cylinder). Type:

0 0 0.6 ENTER

Then, the last value MGED will ask you to enter is the radius. Type:

2.25 ENTER

Your MGED Command Window will look something like:

mged> in base.rcc rc
Enter X, Y, Z of vertex: 0 0 0
Enter X, Y, Z of height (H) vector: 0 0 0.6
Enter radius: 2.25

You will get something like this on your Graphics Window:

11 base

Rather than following this lengthy method, there is another short way to use the in command. It allows entering all the parameters in one go. The above command can also be written as:

in base.rcc rcc 0 0 0 0 0 0.6 2.25 ENTER

Meaning of the above command is:

  • in — Insert a primitive shape

  • base.rcc — Name it base.rcc

  • rcc — Shape should be a right circular cylinder

  • 0 — x value of the vertex is 0

  • 0 — y value of the vertex is 0

  • 0 — z value of the vertex is 0

  • 0 — x value of the height vector is 0

  • 0 — y value of the height vector is 0

  • 0.6 — z value of the height vector is 0.6

  • 2.25 — radius is 2.25

This is how you will be making the rest of the shapes.

Moving on to the upper portion of the pawn.

2. Making the curve

This portion is a little tricky. To make the curve, you will first make a Truncated Right Cone (trc) and then subtract a Torus (tor) from the outer portion of trc.

12 trc
Figure 1. trc
13 tor
Figure 2. tor

To make the trc, type:

in body.trc trc ENTER

The trc should start from the top of the rcc i.e., at the height of 0.6. MGED will ask for the x, y, z values of the vertex (center of the bottom part). Type:

0 0 0.6 ENTER

Then MGED will ask us to enter x, y, z values of height vector. Type:

0 0 1.7 ENTER

The next entry we have to make is the radius of the base which must be the same as the radius of the base.rcc. Therefore, type:

2.25 ENTER

The last value MGED asks for is the top radius. Type:


The graphics window will look like:

14 base and body

To make the curve use the short-hand method of using the in command. Type in the Command Window:

in curve.tor tor 0 0 2.8 0 0 1 2.85 2.35 ENTER


  • 0 0 2.8 are the x, y, z values of the vertex, where:

    2.8 = 0.6 (z value of vertex of body.trc)
        + 1.7 (height of body.trc)
        + 0.5 (radius of the top of body.trc)
  • 0 0 1 are the x, y, z values of the normal vector to make the tube perpendicular to the z-axis.

  • 2.85 is radius1 (radius from Vertex to the center of the tube).

  • 2.35 is radius2 (radius of the tube).

The following image visually explains radius1 and radius2.

15 tor radius1 radius2

3. Making a cylinder for the neck

The cylinder should have vertex 0 0 2.3 where 2.3 came after adding vertex and height of body.trc such that the neck is placed right on top of the body. The height vector of the cylinder should be 0 0 0.5 and the radius should be 1.4. Therefore, type:

in neck.rcc rcc 0 0 2.3 0 0 0.5 1.4 ENTER

4. Making a sphere for the head

Make a sphere with vertex 0 0 3.6 and radius 1.1. Technically the vertex of the sphere should be

3.6 = 2.3  (the vertex of neck.rcc)
    + 0.25 (half of the height of neck.rcc)
    + 1.1  (radius of this sphere)

But we want to cut some portion of the head from below. Type:

in head.sph sph 0 0 3.6 1.1 ENTER

To zoom out of the view click the left mouse button and to zoom back in click the right mouse button. This is what your pawn looks like till now:

16 pawn azel view

Go to View from menu bar and click on Front. This is what your pawn looks in the front view:

17 pawn front view

5. Making a region

Before you can raytrace your design, you have to make of region of all the shapes. Making a region basically means that the shape has uniform material properties i.e., it has mass and occupies space. Constructing a region involves using Boolean operations of union, subtraction, and intersection. To make the region, type:

r pawn.r u base.rcc u body.trc - curve.tor u neck.rcc u head.sph ENTER

This command tells MGED that

  • r — Make a region

  • pawn.r — Name it pawn.r

  • u — Add the volume of the shape

  • - — Subtract the volume of the shape

Here, we are adding the volume of all the shapes except curve.tor, which we are subtracting from body.trc to achieve the required look.

6. Assigning Material Properties to the Region

Now type the following in the MGED command window:

mater pawn.r

MGED will respond with:

Current shader string =
Specify shader. Enclose spaces within quotes.

MGED asks us to enter the type of material we want our region to be made of. To make the region of plastic. Type in:

plastic ENTER

Next, MGED will ask for the color. To make our pawn black in color, type:

0 0 0 ENTER

At last MGED will ask us if we want to inherit the material properties. To answer with NO, type:


7. Clearing the Graphic Window and drawing the new region

We have shapes visible on our graphics window but it is not our region. To clear the graphics Window of the old design and draw the new region, type:

B pawn.r ENTER

18 clear and draw region

You will see your pawn and the curve.tor is dotted which indicates that it subtracted from the region. This command tells MGED to Blast i.e., clear the graphics window and draw the specified region which in our case is pawn.r. The Blast command is a combination of Z and draw commands. On a side note, draw command is used to draw an existing shape. For example, to draw the sphere you made for the head, type : draw head.sph which tells MGED to draw head.sph. If the specified shape does not exist, MGED will give an error.

8. Raytracing your model

Go to the File menu and select Raytrace. A dialog box called the Raytrace Control Panel appears. Next, change the background color by the raytraced by selecting Background Color. A dropdown will appear with some predefined color choices and a color tool. Select the white option. To eliminate the wireframing i.e., the outlines of the shapes, go to Framebuffer (in the Raytrace Control Panel) and select Overlay. The display should appear similar to the following illustration:

19 pawn raytraced

Your pawn is ready to serve the King. Now it’s time to model the rest of the pieces.