I am writing a physics simulation about the collision and reaction of the Rigid Body. And now i have problem in determining the normal vector of two colliding edges. For example, I have 2 rectangulars ( whether or not it's of same size, anything can happens ), and under some situations, they rotate and translate. And finally, they come to contact each other with their edges. How do i determine their refraction vector / normal vector correspondingly? Just as shown as below : /A/\B\ Thanks in advance.