Doom 3 Horizonmapping Techdemo 66c47

Description
We all know Bumpmapping which calculates the pixelcolour depending on the angle
between the pixels normal and the lightdirection but if we take a closer look
we notice that these "shadows" wont get longer or shorter.This is when horizonmapping
becomes handy which allows us to draw a correct shadow which gets longer and shorter.
Although horizonmapping is normally done with additional textures , I decided
that a heightmap (stored in the Normalmaps Bluechannel) should be enough to generate
these "shadows".The Shader simply traces a ray from the current pixelposition back
to the light and checks if hit intersects another pixel, if it does so , the currentpixel must be in the shadowvolume.