Hi all, I want to implement rays emitted from diffraction by a wedge. So I have a wedge with 2 faces ,a common edge and an incident ray. I have the tangent and normal to each face. I calculated the base of the diffracted rays so that it lies in one of the faces. I want to rotate this ray several times about the edge until I reach the other face. I have the rotation matrix. The problem is I can't determine whether my rotation angle is clockwise or anticlockwise. I can rotate in one direction only (since it is a wedge and rays shouldn't go inside the walls). Is there any vector operation I can use to determine this?