Back face culling
We know that dot product between two vertices is : zero when they are perpendicular to each other, greater than zero when angle between them is acute, and less than zero when angle between them is obtuse. This property is used for making a decision to whether render a triangle in a scene with respect to a camera. Only the triangles which are facing the camera needs to be drawn. Camera has a camera direction unit vector(look at vector ) and each triangle has a normal vector. If the dot product of these two vectors is less than zero, it means the camera is facing the triangle and the triangle passes the test.
