Hello & Questions

lisa · 17th February 2008, 09:53 AM

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:
http://jerome.jouvie.free.fr/images/...g-Disabled.png
http://jerome.jouvie.free.fr/images/...led-3Steps.png

17th February 2008, 09:53 AM	#26
lisa Senior Member Professional user Join Date: Mar 2005 Location: Phoenix, AZ Posts: 917	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: http://jerome.jouvie.free.fr/images/...g-Disabled.png http://jerome.jouvie.free.fr/images/...led-3Steps.png Attached Images