Parallax mapping

File:ParallaxMapping.jpg

Example of parallax mapping. The walls are textures with parallax maps. Screenshot taken from one of the base examples of the opensource 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 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 in 2001.

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, and so give 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.

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 is another common name 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.

List of video games that feature parallax mapping

Here is a list of video games that feature parallax mapping. Only seventh generation video game consoles and high-end PCs are capable of rendering parallax mapping in-game, so all of the following games are considered 'next-gen' games.

• Tom Clancy's Splinter Cell: Chaos Theory: PC version, Shader Model 3.0
• Half-Life 2: Episode 2
• Halo 3: Bungie Studios
• Perfect Dark Zero (adds depth to ground rocks/walls)
• Kameo (adds depth to walls and bricks)
• F.E.A.R (adds depth to decals and certain walls)
• The Elder Scrolls IV Oblivion (depth to stone walls)
• Grand Theft Auto IV (bullet holes and wall cracks from collisions)
• Age of Conan: Hyborian Adventures
• BioShock: PC version (some floors and other surfaces)
• Crysis / CryEngine 2: PC-only (many small pebbles that are normally 2D textures are rendered in 3D when in DX10 mode (or CFG hack))

See also

• Parallax

External links

• Comparison from the Irrlicht Engine: With Parallax mapping vs. Without Parallax mapping
• Parallax mapping implementation in DirectX, forum topic
• Parallax Mapped Bullet Holes - Details the algorithm used for F.E.A.R. style bullet holes.
• Interval Mapping
• Parallax Mapping with Offset Limiting
• Steep Parallax Mapping