Software Engineering and Computer Games

7.4. Implementing forces

The base class cForce::force returns a zero vector, but we have ‘global’ force classes cForceGravity, cForceDrag, and cForceVortex which return non-trivial values. We use them in the Ballworld and Dambuilder games, discussed in Chapter 18: Interesting Worlds. We also have ‘relative’ steering force classes liked cForceObjectSeek, cForceClassEvade, and cForceEvadeBullet.

Figure 7.2 is a class diagram of all the forces we provide with the Pop Framework.

Figure 7.2. Class diagram of the cForce child classes

The idea is that each force(cCritter*) method should return a force that the critter will divide by its mass and add ...