Originally Posted by Stuckemuck
This has absolutely nothing to do with raytracing.
It doesn't... it has to do with the claim that physics simulation computations don't take any time. Which is nonsense. Raytracing is physics computations. It was just an example of a physics computation that takes a lot of time.
There might be only 50 objects. But that doesn't mean only 50 computations. If every object can collide with any other, that means, naively, 50 times 50 computations. The more objects you have, the more hairy it gets. And if your objects aren't all simple circles, it gets more complex still. Colliding rectangles is simple enough, colliding rectangles that can rotate at any angle, well... go on... you tell us how you would do it. If you have a pile of objects, as is typical on Angry Birds, every single object is involved in one or more collisions every single frame
so you had better know what you are doing. Each collision is roughly equivalent, in terms of maths, to ray tracing a single pixel. So, go on. Ray trace 50 pixels in 1/50th of a second.