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Old 17th February 2008, 09:53 AM   #26
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Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 917
Default Re: Hello & Questions

Parallax Mapping

When I said earlier there was something cool you could do with a displacement map other than displace geometry, I was thinking about parallax mapping. To clarify, parallax mapping isn't another map type; it's a technique that combines a normal map with a displacement map to create an even more convincing illusion of depth.

One of the limitations of normal maps is that since they don't actually move the geometry--they only change the surface normal--they can't occlude the geometry that is "behind" any raised surfaces. In addition, the human eye expects that objects further away will slide past at slower speed than objects that are nearer. This phenomena is called "parallax". The result of these limitations means that at shallow angles, normal maps become less convincing. They either appear less "deep", or the illusion falls apart entirely.

Parallax mapping corrects both of these problems. Parallax mapping uses a displacement map to determine which pixel would actually be seen based on the current view angle. It also causes further pixels to scroll at a different speed.

Unfortunately, this is again difficult to convey in a still image. Here are two different images of the cube with parallax off and parallax on.

This pair of images shows the effect even more dramatically:
Attached Images
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