Collisions

I haven't done this myself but my approach would probably be to find the intersection of the ray with the plane defined by the triangle, then test to see if that intersection point was inside of the triangle.

Hi,

There are a number of ways to intersect a ray and a triangle. Most if not all of them are flawed in some way, but some are arguably 'better', or at least more robust, than others.

Could you tell us what you're using the intersection test for? For some situations a simpler but less robust test may be adequate, but it's hard to make a recommendation without knowing more about the application.