chapter  15
Ray Tracing
Pages 36

In ray tracing, the path (ray) along the line of sight starting from the camera focal point (center of projection) and passing through each pixel is followed as it travels through the three-dimensional scene, and it registers what the observer sees along this direction [Appe68]. As the ray encounters geometric entities, it is specularly reflected, refracted, or attenuated (and completely absorbed of course) depending on the material properties of the objects. Hidden surface elimination (in object space and not image space) happens as an integral part of this process because the ray encounters surface interfaces closer to the viewer first while it travels through the three-dimensional world.