Editing Ambient occlusion (section)

{{short description|Computer graphics shading and rendering technique}}
[[File:AmbientOcclusion German.jpg|thumb|The ambient occlusion map (middle image) for this scene darkens only the innermost angles of corners.]]

In [[3D computer graphics]], [[3D modeling|modeling]], and [[Computer animation|animation]], '''ambient occlusion''' is a [[shading]] and [[Rendering (computer graphics)|rendering]] technique used to calculate how exposed each point in a scene is to [[Shading#Ambient lighting|ambient lighting]]. For example, the interior of a tube is typically more occluded (and hence darker) than the exposed outer surfaces, and becomes darker the deeper inside the tube one goes.

Ambient occlusion can be seen as an accessibility value that is calculated for each surface point.<ref>{{cite book| author=Miller, Gavin| chapter=Efficient algorithms for local and global accessibility shading| title=Proceedings of the 21st annual conference on Computer graphics and interactive techniques| year=1994| pages=319–326}}</ref> In scenes with open sky this is done by estimating the amount of visible sky for each point, while in indoor environments only objects within a certain radius are taken into account and the walls are assumed to be the origin of the ambient light. The result is a [[Diffuse reflection|diffuse]], non-directional shading effect that casts no clear shadows, but that darkens enclosed and sheltered areas and can affect the rendered image's overall tone. It is often used as a [[Image editing|post-processing]] effect.

Unlike local methods such as [[Phong shading]], ambient occlusion is a global method, meaning that the illumination at each point is a function of other geometry in the scene. However, it is a very crude approximation to full [[global illumination]].  The appearance achieved by ambient occlusion alone is similar to the way an object might appear on an [[overcast]] day.

The first method that allowed simulating ambient occlusion in real time was developed by the research and development department of [[Crytek]] ([[CryEngine |CryEngine 2]]).<ref>{{cite web |url=https://vr.arvilab.com/blog/ambient-occlusion |title=AMBIENT OCCLUSION: AN EXTENSIVE GUIDE ON ITS ALGORITHMS AND USE IN VR|publisher=ARVIlab |access-date=2018-11-26}}</ref> With the release of hardware capable of real time ray tracing ([[GeForce 20 series]]) by [[Nvidia]] in 2018, [[Ray tracing (graphics)|ray traced]] ambient occlusion (RTAO) became possible in games and other real time applications.<ref>{{cite AV media|url=https://www.youtube.com/watch?v=yag6e2Npw4M |archive-url=https://ghostarchive.org/varchive/youtube/20211212/yag6e2Npw4M| archive-date=2021-12-12 |url-status=live|publisher=Nvidia|title=Ray Traced Ambient Occlusion}}{{cbignore}}</ref> This feature was added to the [[Unreal Engine]] with version 4.22.<ref>{{cite news|url=https://www.extremetech.com/computing/285701-unreal-engine-adds-support-for-dx12-raytracing|title=Unreal Engine Adds Support for DX12 Raytracing|work=ExtremeTech}}</ref>