In fact, if I do my job correctly, the player won t notice the collision system at all. Actually, that s my goal. The whole physics system should work well enough that people don t notice that it s there. Also notice that I said well enough. Take modeling gravity, for example.
Gravity is actually kind of a pain to get to work correctly.
You can t just check every Actor against every object in the world every frame that s just too slow. You want to minimize the number of collisions you process every frame. So, if an Actor is standing on a flat surface, there s no real reason that gravity should affect it. Since you already know how the Actor will collide with the plain that it stands on, you can throw out gravity entirely. With gravity gone, the Actor isn t trying to constantly resolve collisions with the floor, which means the system runs faster.