Iñigo Quílez posted a recent presentation on the techniques used in the “Slisesix” rgba demo. By procedurally generating a distance field representation of the scene, a fast, space-skipping raycast can be performed. Using a distance field representation allows other tricks such as fast AO and soft shadow techniques because information such as the distance and direction of the closest occluders are implicit in the representation. Alex Evans talked about using this type of technique ( see Just Blur and Add Noise) but in his proposed implementation the distance field came from rasterizing geometry into slices and blurring outward.
Presentation: Rendering Worlds with Two Triangles