Parallax mapping: Difference between revisions

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<!-- Deleted image removed: [[Image:ParallaxMapping.jpg|thumb|300px|right|Image:ParallaxMapping.jpg| Example of parallax mapping. The walls are [[Texture (visual arts)|texture]]d with parallax maps. Screenshot taken from one of the base examples of the [[open source]] [[Irrlicht Engine|Irrlicht 3d engine]].]] -->

'''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 (computer graphics)|rendering]] applications such as [[video game]]s. To the end user, this means that [[texture mapping|textures]] such as [[stone wallswall]]s 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., in 2001.<ref name="Kaneko">Kaneko, T., et al., 2001. [https://www.researchgate.net/profile/Susumu_Tachi/publication/228583097_Detailed_shape_representation_with_parallax_mapping/links/02e7e518259abdc882000000.pdf Detailed Shape Representation with Parallax Mapping]. In Proceedings of ICAT 2001, pp. 205-208.</ref>

Parallax mapping is implemented by displacing the [[texture coordinatescoordinate]]s 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 culling|occlusion]]. Subsequent enhancements have been made to the algorithm incorporating iterative approaches to allow for occlusion and accurate silhouette rendering.<ref name="Tatarchuk">Tatarchuk, N., 2005. [http://ati.amd.com/developer/SIGGRAPH05/Tatarchuk-ParallaxOcclusionMapping-Sketch-print.pdf Practical Dynamic Parallax Occlusion Mapping] Siggraph presentations</ref>

==Steep parallax mapping==

'''Steep parallax mapping''' is one name for the class of algorithms that trace rays against heightfields[[heightfield]]s. 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 (computer graphics)|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.