Find the normal angle of the face of a triangle in 3D, given the co-ordinates of its vertices

Question

As you may be able to tell from this screenshot, I am trying to make a physics engine for a platformer I am working on, but I have run into a definite problem: I need to be able

Answer 1

There are 2 normals to the triangle (of course) and the one you get from standard algorithms depends on the order of ther vertices. Quoting wiki

"For a polygon (such as a triangle), a surface normal can be calculated as the vector cross product of two (non-parallel) edges of the polygon."

But the direction of the normal depends on the order of points chosen, you can calculate it and decide using some other heuristics whether the reverse vector is the normal you are interested in.