http://www.cs.cmu.edu/afs/cs/academic/class/15462-s09/www/lec/13/lec13.pdf Eye/Primary rays: from camera into scene Shadow rays: rays from surface intersection point toward light source Reflection rays: from surface intersection point in mirror direction Transmission rays: from surface intersection point in refracted direction Algorithm: - Send ray from camera through each pixel into scene - Compute point of closest intersection with scene object - Shade that point by computing shadow rays - Spawn reflection and refraction/transmission rays and recurse When do we stop tracing? - When the ray leaves the scene - When the ray's contribution becomes too small