Events, Triggers, and Explosions - Learning Game Physics with Bullet Physics and OpenGL - page 104

Summary
Very little game logic can be built around a physics engine without a collision event
system, so we made Bullet broadcast collision and separation events to our applica-
tion so that it can be used by our game logic. This works by checking the list of man-
ifolds, and creating logic that keeps track of important changes in these data struc-
tures.
Once we have these collision events, we need to do something with them, and we
explored how to use a collision event between a box and an invisible trigger volume
to instantiate a new object in our world, and how to capture these events within an
instant of time when an explosion is generated.
In the next chapter, we will explore some of the more unusual types of collision shapes
offered by Bullet.