{{Short description|Technique in 3D computer graphics}} '''Alpha mapping''' or '''transparency mapping''' is a technique in 3D computer graphics involving the use of texture mapping to designate the amount of transparency/translucency of areas in a certain object.<ref name="birn"/><ref name="goulekas"/>
Alpha mapping is used when the given object's transparency is not consistent: when the transparency amount is not the same for the entire object and/or when the object is not entirely transparent.<ref name="birn"/> If the object has the same level of transparency everywhere, one can either use a solid-color alpha texture or an integer value.{{citation needed|date=October 2025}}
The alpha map is often encoded in the alpha channel of an RGBA texture used for coloring, but can also exist as a standalone greyscale or coloured texture.<ref name="birn"/><ref name="goulekas"/> An alpha map is often used in conjunction with a textured flat surface as part of billboarding.<ref name="birn"/>
== Blending methods == Alpha mapping is typically used in combination with blending operations in the rendering pipeline to combine transparent fragments with background colors. The most common approach is alpha blending, where the final pixel color is computed by mixing the source color with the destination color based on the alpha value.<ref>{{cite web |title=Blending |url=https://www.khronos.org/opengl/wiki/Blending |website=Khronos OpenGL Wiki |publisher=Khronos Group |access-date=27 January 2026 }}</ref>
In real-time graphics systems, different blending modes can be selected depending on the desired visual effect, such as standard transparency, additive blending for effects like fire or light glows, or multiplicative blending for shading overlays. Graphics APIs such as OpenGL and Direct3D define these blending operations as part of their fixed-function or programmable pipelines.<ref>{{cite web |title=Alpha Blending (Direct3D) |url=https://learn.microsoft.com/en-us/windows/win32/direct3d9/alpha-blending |website=Microsoft Learn |publisher=Microsoft |access-date=27 January 2026 }}</ref>
==See also== * {{section link|Mask (computing)|Image masks}}
==References== <references>
<ref name="birn">{{cite book |last1=Birn |first1=Jeremy |title=Digital Lighting and Rendering |date=4 November 2013 |publisher=Pearson Education |isbn=978-0-13-343917-5 |language=en|pages=288-289}}</ref> <ref name="goulekas">{{cite encyclopedia |last1=Goulekas |first1=Karen|title= transparency mapping |encyclopedia=Visual Effects in a Digital World: A Comprehensive Glossary of Over 7000 Visual Effects Terms |date=27 July 2001 |publisher=Morgan Kaufmann |isbn=978-0-12-293785-9 |page=520 |language=en}}</ref>
</references>
Category:3D imaging Category:Texture mapping Category:Visual effects {{Texture mapping techniques}} {{Compu-graphics-stub}}