Parallax mapping

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Parallax Mapping (also, Photonic Mapping, 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 wooden floorboards) will have more apparent depth and realism with less of an influence on the speed of the game.

Parallax mapping is done by displacing the texture coordinates such that the texture occludes itself in accordance with a height map. Next-generation 3D applications may employ parallax mapping as new graphics algorithms are developed.

From F.E.A.R., a bullet hole with Parallax mapping used to create the illusion of depth.

From F.E.A.R., same as before, but viewed at an angle.

From F.E.A.R., when viewed at an extreme angle, the illusion of depth disappears.

An easy way to understand this concept is to close one eye, take a pencil, point it at your eye, and move your head left and right. Parallax mapping takes that pixel on the far left of the pencil when it was facing you directly and stretches it accordingly to simulate your angle in comparison to the pencil.

Parallax mapping is also a way of faking displacement mapping where the actual geometric position of points surface is displaced along the surface normal according to the values stored into the texture: in Parallax mapping, like in normal and bump mapping, the silhouette of the object is unaffected.