   Triangle-Triangle collision testing (sorry)
  This must be out there already, feel free to point out a past thread rather than reply.This seems to me the fastest, easiest way to tell if 2 triangles intersect:For tri 1, see if any of its edges intersect tri 2. Then reverse the test.There must be some tricks when you test two convex shapes ie boxes since they are closed surfaces too? 
  separation axis algorithm is the fastest test around. for tri/tri, you can apply the same principle. If you like edge intersections, you can also intersect one of the triangle edges with the other triangle plane, and check is the segment defined by the points of intersection intersects the other triangle.  