Game Development Reference
Figure 9-1. 2D rigid-body example
In this simulation, the world coordinate system has its x-axis pointing to the right, its
y-axis pointing down toward the bottom of the screen, and the z-axis pointing into the
screen. Even though this is a 2D example where all motion is confined to the x-y plane,
you still need a z-axis about which the hovercraft will rotate. Also, the local, or body-
fixed, coordinate system has its x-axis pointing toward the front of the hovercraft, its
y-axis pointing to the starboard side, and its z-axis into the screen. The local coordinate
system is fixed to the rigid body at its center of gravity location.
The hovercraft modeled in this simulation is a simplified version of the hovercraft we'll
model in Chapter 17 . You can refer to Chapter 17 for more details on that model. For
convenience we repeat some of the basic properties of the model here. Figure 9-2 illus‐
trates the main features of the model.