Editing 2.5D (section)

===Bump, normal and parallax mapping===
{{Main|Bump mapping|Normal mapping|Parallax mapping}}
'''Bump mapping''', '''normal mapping''' and '''parallax mapping''' are techniques applied to [[texture mapping|textures]] in [[3D rendering]] applications such as [[video game]]s to simulate bumps and wrinkles on the surface of an object without using more [[polygonal modeling|polygon]]s. 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.

'''Bump mapping''' is achieved by perturbing the [[surface normal]]s of an object and using a [[grayscale]] image and the perturbed normal during illumination calculations. The result is an apparently bumpy surface rather than a perfectly smooth surface although the surface of the underlying object is not actually changed. Bump mapping was introduced by Blinn in 1978.<ref name="Blinn">Blinn, James F. [http://dl.acm.org/citation.cfm?id=507101 "Simulation of Wrinkled Surfaces"], Computer Graphics, Vol. 12 (3), pp.&nbsp;286–292 SIGGRAPH-ACM (August 1978)</ref>

[[File:Bump-map-demo-full.png|thumb|right|300px|A sphere without [[bump mapping]] (left). The bump map to be applied to the sphere (middle). The sphere with the bump map applied (right).]]

In '''normal mapping''', the unit [[Vector (geometric)|vector]] from the shading point to the light source is [[dot product|dotted]] with the unit vector normal to that surface, and the dot product is the intensity of the light on that surface. Imagine a polygonal model of a sphere—you can only approximate the shape of the surface. By using a 3-channel bitmapped image textured across the model, more detailed normal vector information can be encoded. Each channel in the bitmap corresponds to a spatial dimension (''x'', ''y'' and ''z''). These spatial dimensions are relative to a constant coordinate system for object-space normal maps, or to a smoothly varying coordinate system (based on the derivatives of position with respect to texture coordinates) in the case of tangent-space normal maps. This adds much more detail to the surface of a model, especially in conjunction with advanced lighting techniques.

'''Parallax mapping''' (also called '''offset mapping''' or '''virtual displacement mapping''') is an enhancement of the bump mapping and normal mapping techniques 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.