Modeling Rook

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):

In Front view:

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.

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:

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).

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

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:

ls ENTER

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:

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.

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: