Steep parallax mapping with self shadowing
This recipe builds on the previous one, parallax mapping, so if you haven't already done so, you may want to review that recipe prior to reading this one.
Steep parallax mapping is a technique, first published by Morgan McGuire and Max McGuire in 2005. It improves upon parallax mapping, producing much better results at the cost of more fragment shader work. Despite the additional cost, the algorithm is still well suited to real-time rendering on modern GPUs.
The technique involves tracing the eye ray through the height map in discrete steps until a collision is found in order to more precisely determine the appropriate offset for the texture coordinate. Let's revisit the diagram from the previous recipe, but this time, we'll break up the height map into n discrete levels (indicated by the dashed lines):
As before, our goal is to offset the texture coordinates so that the surface is shaded based on the bump surface, not the true surface. The point...
