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Parallax mapping 93
Parallax mapping
Parallax mapping (also called offset
mapping or virtual displacement
mapping) is an enhancement of the bump
mapping or normal mapping techniques
applied to textures in 3D rendering
applications such as video games. To the
end user, this means that textures such as
stone walls will have more apparent depth
and thus greater realism with less of an
influence on the performance of the
simulation. Parallax mapping was
introduced by Tomomichi Kaneko et al. [1] in
2001.
Example of parallax mapping. The walls are textured with parallax maps.
Screenshot taken from one of the base examples of the open source Irrlicht 3d
Parallax mapping is implemented by displacing the texture coordinates at a point on the rendered polygon by a
function of the view angle in tangent space (the angle relative to the surface normal) and the value of the height map
at that point. At steeper view-angles, the texture coordinates are displaced more, giving the illusion of depth due to
parallax effects as the view changes.
Parallax mapping described by Kaneko is a single step process that does not account for occlusion. Subsequent
enhancements have been made to the algorithm incorporating iterative approaches to allow for occlusion and
accurate silhouette rendering. [2]
Steep parallax mapping
Steep parallax mapping is one name for the class of algorithms that trace rays against heightfields. The idea is to
walk along a ray that has entered the heightfield's volume, finding the intersection point of the ray with the
heightfield. This closest intersection is what part of the heightfield is truly visible. Relief mapping and parallax
occlusion mapping are other common names for these techniques.
Interval mapping improves on the usual binary search done in relief mapping by creating a line between known
inside and outside points and choosing the next sample point by intersecting this line with a ray, rather than using the
midpoint as in a traditional binary search.
References
engine.
[1] Kaneko, T., et al., 2001. Detailed Shape Representation with Parallax Mapping (http:/ / vrsj. t. u-tokyo. ac. jp/ ic-at/ ICAT2003/ papers/
01205. pdf). In Proceedings of ICAT 2001, pp. 205-208.
[2] Tatarchuk, N., 2005. Practical Dynamic Parallax Occlusion Mapping (http:/ / developer. amd. com/ media/ gpu_assets/
Tatarchuk-ParallaxOcclusionMapping-Sketch-print. pdf) Siggraph presentation
External links
• Comparison from the Irrlicht Engine: With Parallax mapping (http:/ / www. irrlicht3d. org/ images/
parallaxmapping. jpg) vs. Without Parallax mapping (http:/ / www. irrlicht3d. org/ images/ noparallaxmapping.
jpg)
• Parallax mapping implementation in DirectX, forum topic (http:/ / www. gamedev. net/ community/ forums/
topic. asp?topic_id=387447)