Displacement mapping: Difference between revisions

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{{short description|Computer graphics technique}}

{{No footnotes|date=August 2011}}

{{More citations needed|date=June 2023}}

[[Image:Displacement.jpg|thumb|Displacement mapping]]

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'''Displacement mapping''' is an alternative computer graphics technique in contrast to [[bump mapping]], [[normal mapping]], and [[parallax mapping]], using a ([[procedural texture|procedural]]-) [[texture mapping|texture-]] or [[heightmap|height map]] to cause an effect where the actual geometric position of points over the textured surface are ''displaced'', often along the [[Locally|local]] [[surface normal]], according to the value the texture function evaluates to at each point on the surface. It gives surfaces a great sense of depth and detail, permitting in particular self-occlusion, [[self-shadowing]] and silhouettes; on the other hand, it is the most costly of this class of techniques owing to the large amount of additional geometry.

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|image1=Displacement.jpg

For years, displacement mapping was a peculiarity of high-end rendering systems like [[PhotoRealistic RenderMan]], while realtime [[Application programming interface|APIs]], like [[OpenGL]] and [[DirectX]], were only starting to use this feature. One of the reasons for this is that the original implementation of displacement mapping required an adaptive [[Tessellation#Tessellations and computer models|tessellation]] of the surface in order to obtain enough [[micropolygon]]s whose size matched the size of a pixel on the screen.

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|caption1=Displacement mapping in mesh

|alt1=Cartesian transport

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|caption2=Displacement mapping with SVG filter effects

|alt2=Polar transport

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'''Displacement mapping''' is an alternative computer graphics technique in contrast to [[bump mapping|bump]], [[normal mapping|normal]], and [[Parallax mapping|parallax]] [[Texture mapping|mapping]], using a ([[proceduralImage texture|procedural]]-) [[texture mapping|texture-]] or [[heightmap|height map]] to cause an effect where the actual geometric position of points over the textured surface are ''displaced'', often along the [[Locally|local]] [[surface normal]], according to the value the texture function evaluates to at each point on the surface.<ref>{{Cite web |title=Chapter 8. Per-Pixel Displacement Mapping with Distance Functions |url=https://developer.nvidia.com/gpugems/gpugems2/part-i-geometric-complexity/chapter-8-pixel-displacement-mapping-distance-functions |access-date=2023-05-10 |website=NVIDIA Developer |language=en}}</ref> It gives surfaces a great sense of depth and detail, permitting in particular self-occlusion, [[self-shadowing]] and silhouettes; on the other hand, it is the most costly of this class of techniques owing to the large amount of additional geometry.

For years, displacement mapping was a peculiarity of high-end rendering systems like [[PhotoRealistic RenderMan]], while realtime [[Application programming interface|APIs]], like [[OpenGL]] and [[DirectX]], were only starting to use this feature. One of the reasons for this is that the original implementation of displacement mapping required an adaptive [[Tessellation#Tessellations and (computer modelsgraphics)|tessellation]] of the surface in order to obtain enough [[micropolygon]]s whose size matched the size of a pixel on the screen.{{citation needed|date=March 2020}}

==Meaning of the term in different contexts==

Displacement mapping includes the term mapping which refers to a [[texture mapping|texture map]] being used to [[modulate]] the displacement strength. The displacement direction is usually the local surface normal. Today, many [[Rendering (computer graphics)|renderer]]s allow [[shader|programmable shading]] which can create high quality (multidimensional) [[procedural texture]]s and [[texture synthesis|patterns]] at arbitraryarbitrarily high frequencies. The use of the term mapping becomes arguable then, as no texture map is involved anymore. Therefore, the broader term '''displacement''' is often used today to refer to a super concept that also includes displacement based on a texture map.

Renderers using the [[Reyes rendering|REYES]] [[algorithm]], or similar approaches based on [[micropolygon]]s, have allowed displacement mapping at arbitrary high frequencies since they became available almost 20 years ago.

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Recent developments seem to indicate that some of the renderers that use sub-pixel displacement move towards supporting higher level geometry too. As the vendors of these renderers are likely to keep using the term sub-pixel displacement, this will probably lead to more obfuscation of what displacement mapping really stands for, in [[3D computer graphics]].

In reference to Microsoft's proprietary [[High Level Shader Language]], displacement mapping can be interpreted as a kind of "vertex-texture mapping" where the values of the [[texture map]] do not alter pixel colors (as is much more common), but instead change the position of vertices. Unlike bump, normal and parallax mapping, all of which can be said to "fake" the behavior of displacement mapping, in this way a genuinely ''rough'' surface can be produced from a texture. It has to be used in conjunction with adaptive [[tessellation]] techniques (that increases the number of rendered polygons according to current viewing settings) to produce highly detailed meshes.{{citation needed|date=March 2020}}

==See also==

* [[Texture mapping]]

* [[Bump mapping]]

* [[Normal mapping]]

* [[Parallax mapping]]

* [[Relief mapping (computer graphics)]]

* [[Heightmap]]

* [[Sculpted prim]]

==Further reading==

*[httphttps://wikiarchive.blender.org/wiki/index.php/Manual/Displacement_Maps/ Blender Displacement Mapping]

*[https://garagefarm.net/blog/how-displacement-maps-work-and-how-to-optimize-them-in-v-ray-part-1/ Vray Displacement Mapping]

*[http://www.inf.ufrgs.br/%7Eoliveira/RTM.html Relief Texture Mapping] website

* [http://www.inf.ufrgs.br/%7Eoliveira/pubs_files/Policarpo_Oliveira_Comba_RTRM_I3D_2005RTM.pdf ''Real-Timehtml Relief Texture Mapping on Arbitrary Polygonal Surfaces''] paperwebsite

* {{usurped|1=[https://web.archive.org/web/20150419215321/http://sunandblackcat.com/tipFullView.php?l=eng&topicid=28 Parallax Occlusion Mapping in GLSL on sunandblackcat.com]}}

* [http://www.inf.ufrgs.br/%7Eoliveira/pubs_files/Policarpo_Oliveira_RTM_multilayer_I3D2006Policarpo_Oliveira_Comba_RTRM_I3D_2005.pdf ''Real-Time Relief Mapping ofon Non-Height-FieldArbitrary SurfacePolygonal DetailsSurfaces''] paper

*[http://graphics.cs.brown.edu/games/SteepParallax/index.html ''Steep Parallax Mapping''] website

* [http://www.iitinf.bmeufrgs.hubr/~szirmay%7Eoliveira/egdisfinal3pubs_files/Policarpo_Oliveira_RTM_multilayer_I3D2006.pdf ''StateRelief of the artMapping of displacement mapping onNon-Height-Field theSurface gpuDetails''] paper

*''[https://web.archive.org/web/20110816214356/http://sirkan.iit.bme.hu/~szirmay/egdisfinal3.pdf State of the art of displacement mapping on the gpu]'' paper

==References==

{{reflist}}

* [[{{Texture mapping]] techniques}}

[[Category:Texture mapping]]