Killer Game Programming in Java

Modeling a Limb

The main job of the Limb class is to convert limb information into a Java 3D subgraph, like the one in Figure 20-14.

The start and end joints are represented by TransformGroups. startLimbTG isn't created by the limb but obtained from the parent limb. It's the parent's endLimbTG, and in this way are children attached to parents. The limb creates endLimbTG, which is positioned along the y-axis, 90 percent of the way along the length of the limb's shape. Child limbs can be attached to endLimbTG, meaning that they will overlap the

Figure 20-14. The subgraph representing a limb

parent limb shape. This enhances the effect that the limbs are connected, especially when a limb is rotated.

In between the joint TransformGroups are four more TransformGroups and a LatheShape3D node representing the limb shape and its position. These are the details hidden by the thick gray lines between the TransformGroups in Figure 20-10. Each of those lines should be expanded into the five nodes surrounded by the gray dotted box in Figure 20-14.

orientTG is used to orient the shape initially. The other TransformGroups are located below it as its children, so they view the new orientation as pointing along the positive y-axis. The xAxisTG, yAxisTG, and zAxisTG TransformGroups are employed to rotate the limb around the x-, y-, and z-axes at runtime. The separation of these rotations into three parts ...