''It might seem that we would need only to run a conventional ray tracer "backward" from the light sources to the eye to achieve these effects. This concept has been called backward ray tracing, to indicate that it runs in the reverse direction from regular ray tracing, but it is also known as forward ray tracing to stress that it follows the actual path from the lights to the eye. We call it ray tracing from the light sources to avoid confusion!''

Foley et al., Computer Graphics: Principles and Practice, p. 792.