Modeling Rook

20 rook

Before you start modeling this piece, create a new database named rook.g. Create this new database as we did in the previous case.

Type in the Command Window:

opendb rook.g ENTER

If you didn’t open the MGED Command Window again and used the above command in the already opened window, you will see that the raytraced image didn’t disappear. So, in order to get the blue screen back for making other shapes, go to Modes from the menu bar and uncheck the Framebuffer Active option by clicking on it.

Now, you are ready to model the rook. Since you are already familiar with the in command, therefore you will be using the shorthand method of this command for making shapes.

1. Making the base and body

Making the base is the same as we did in pawn. Type the following in the MGED command window:

in base.rcc rcc 0 0 0 0 0 0.8 2.25 ENTER

This command will make a cylinder at vertex 0 0 0 with height 0 0 0.8 and radius 2.25.

As we did in pawn, we will create the body using two shapes: rcc and trc. To create the body, type:

in body.trc trc 0 0 0.8 0 0 3 2.25 1.1 ENTER

This command creates a trc at vertex 0 0 0.8 with height 0 0 1.5, radius of the base 2.25 and radius of top 1.1. Now, to create the curve, type:

in curve.tor tor 0 0 3 0 0 1 3.6 2.6 ENTER

In pawn, we had the vertex at a distance greater than the height of trc because we wanted the curve to start right when the body starts but in this case we want to have a straight portion before the curve part. So, we have the vertex at 0 0 3. The normal vector is 0 0 1 to make our shape perpendicular to z-axis. Radius 1 is 3.6 and Radius 2 is 2.6.

You will get something like this (after zooming out by clicking the left mouse button, to zoom in click the right mouse button):

21 rook azel view

In Front view:

22 rook front view

2. Constructing the hollow cylinder for the head

Now comes the tricky part; we need to model the head. To understand it completely, type Z to clear the Graphic Window temporarily. Make sure your Command Window is active while you do so.

One of the common mistakes we make as a beginner is that we forget to make the Command Window active and end up typing on the Graphics Window. For those who have typed Z but the design started rotating, you need not worry. Go to the View option on the Menu bar and click on the last option Zero . Now to get back your design in the original orientation, go to View option once again and click on the view you were previously in. By default, the view is az35,el25 . Click on this option and you are ready to move further.

To make a cylinder for neck:

in neck.rcc rcc 0 0 3.8 0 0 1 1.75 ENTER

The value of vertex 0 0 3.8 came after adding the height of the base and the body. I hope you are familiar with how we use the value of the vertex.

For the head, we have to make a hollow cylinder first, which comes after subtracting a cylinder from another cylinder with a comparatively larger radius. Therefore, the vertex and height of both the inner and outer cylinders should be the same. The radius of the inner cylinder depends on the thickness of the required hollow cylinder.

To construct the outer cylinder type:

in outer.rcc rcc 0 0 4.8 0 0 0.6 1.75 ENTER

To make the inner cylinder with the same vertex and height, type:

in inner.rcc rcc 0 0 4.8 0 0 0.6 1.25 ENTER

Your graphics window will look like:

23 rook neck

3. The first cuboid for the rook head

Generally, when you see a rook piece its head seems as in a hollow cylinder is cut in pieces. To replicate that, we will make two cuboids with length equal to or greater than the radius of the outer cylinder, and height equal to the height of either one of the cylinders (both inner and outer cylinders have the same height). Then you will subtract these cuboids from the hollow cylinder. Now you will make two cuboids that can be placed perpendicular to each other like an X mark (a cross). For that, we will make rpp (Rectangular Parallelopiped).

To make the first one, type:

in cross1.rpp rpp ENTER

Then MGED will ask for XMIN, XMAX, YMIN, YMAX, ZMIN, ZMAX values. Type:

-1.75 1.75 -0.5 0.5 4.8 5.4 ENTER

To check the coordinate system, press m making sure the Graphics window is active. You won’t see the coordinate lines because you are a little above the origin. So, left-click on the graphics window to zoom out. You will see that the Z-axis is along the diameter. Therefore the XMIN should be -1.75 (radius of the outer cylinder) and XMAX should be 1.75. The breadth is along the Y-axis. Therefore, -0.5 for YMIN and 0.5 for YMAX. The height is along the Z-axis. Since the cuboid must start from the base of the outer cylinder, therefore ZMIN is 4.8 and ZMAX is 5.4 i.e., ZMIN plus height of outer cylinder (0.6).

24 rook neck cuboid

4. Constructing a cuboid perpendicular to the first

Since you need another cuboid perpendicular to the first one, we use the clone command as follows:

clone -r 0 0 90 cross1.rpp ENTER

You are not yet familiar with the clone command which will be explained in detail in the Modeling Chessboard section.

Now, MGED will respond with

cross101.rpp {cross101.rpp)

This means we have both shapes for the cross. To view the other shape, type:

draw cross101.rpp ENTER

You can look at the head from different views by changing it from the View Menu. Don’t get discouraged if you only see the head, the other shapes are still right there but since we cleared the Graphics Window using Z they are not visible. To get the list of all the shapes in your database, type in the command window:


You will get a list of all your shapes. To view all your shapes on the Graphics Window, use the draw command. Draw all the remaining shapes as follows:

draw base.rcc body.trc curve.tor ENTER

Make sure to add spaces between the names. This command tells MGED to draw the three specified shapes. In the az35, el25 view, your design will look like:

25 rook azel view

Before you raytrace, make the region of the rook:

r rook.r u base.rcc u body.trc - curve.tor u neck.rcc u outer.rcc - inner.rcc - cross1.rpp - cross101.rpp ENTER

Here we have subtracted curve.tor from body.trc to make the curve. Subtracted inner.rcc from outer.rcc to make a hollow cylinder and subtracted both cuboids cross1.rpp and cross101.rpp from the outer hollow cylinder to give the finishing look. This command makes a region named rook.r.

5. Assigning material properties and raytracing

We will assign material properties as we did in the case of pawn. We will use the shorthand method of the mater command. Type:

mater rook.r plastic 0 0 0 0 ENTER

Don’t forget to clear the graphics window and redraw the design using Blast command as follows:

B rook.r ENTER

Now, raytrace your design from the File menu. Change the background color to white and select the Overlay option from Framebuffer option in the Raytrace Menu Bar. For details check the instructions in the previous model of the pawn. This is what we get after raytracing:

26 rook rt azel view
Figure 1. az35, el25 view
27 rook rt left view
Figure 2. Left view