Simple collision tests

At the lowest level, collision detection usually requires testing a pair of model primitives to determine whether they intersect. In the case of models formed from 3D triangles, then we need a method that determines whether two triangles intersect. This is similar to the ray-triangle intersection test that was needed for visual rendering in Section 7.1, and involves basic tools from analytic geometry, such as cross products and plane equations. Efficient methods are given in [107,220].