What are Jaggies
We have diffuse and specular lighting and shadows, things look pretty nice . . . except for those jaggies. What are jaggies you say? They are technically called aliasing, and it comes from the fact that computer screens are made up out of pixels. Pixels have a size, while very small, they still have an area. Aliasing happens when say a line goes through they corner of a two pixels. Well a pixel has to turn all of itself on or none. It can't have half a pixel on. And this creates those jagged edges. Look here at this example.
So far so good, things are looking pretty spiffy. But there is still something lacking as far as lighting goes. Any ideas? There are no shadows! This must be fixed, we mush have shadows. So how do we do shadows? We cast a ray into the scene, it hits an object and from that hit point we cast another ray to all the lights in a scene.