Screen Space Ambient Occlusion (SSAO): Difference between revisions

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[[{{ns:6}}:Screen space ambient occlusion.jpg|thumb|400px|Screen Space Ambient Occlusion applied to a typical 3D scene.]]
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'''Ambient Occlusion (AO)''' is a type of [[lighting]] technique applied in-game to create more realistic lighting. AO simulates soft shadows created by two surfaces that are close together. Typically AO is accomplished through '''[[Wikipedia:Screen Space Ambient Occlusion|Screen Space Ambient Occlusion (SSAO)]]''', which is a simplified way to fake realistic AO with shaders in a process fast enough for real-time rendering.
{{Todo|Document about HBAO, alternative to SSAO which can be forced through GPU driver control panel (or NVIDIA Profile Inspector).}}
[[File:AmbientOcclusionExample.jpg|right|210px|thumb|An example of traditional ''prerendered'' ambient occlusion in Blender 3D. SSAO attempts to mimic this look in real-time.]]


SSAO works by examining an onscreen pixel, and then comparing its location in the depth buffer (i.e. how far it is away from the player) to the pixels around it. Pixels which are close together but not coplanar (on the same face) are shaded to simulate soft shadows. To maintain playable framerates, it is not possible to sample every pixel every frame, so random sampling is used, which will inevitably create noise/grain which may be more noticeable with movement. To counter this, the SSAO pass is often Gaussian blurred to remove such grain.
{{note | Not to be confused with baked ambient occlusion on models!}}


=SSAO in the Source Engine=
{{TODO|Expand the article to include different methods of SSAO. The method described is one of many.}}<br>
{{TODO|Write a tutorial on creating an SSAO shader and implementing it into the engine. See [[Shader Authoring]].}}
 
'''Screen Space Ambient Occlusion''' ('''SSAO''') works by examining an onscreen pixel, and then comparing its location in a [[depth buffer]] to the pixels around it. Pixels which are close together but not coplanar (on the same face) are shaded to simulate soft shadows. To maintain playable framerates, it is not possible to sample every pixel every frame, so random sampling is used, which will inevitably create noise/grain which may be more noticeable with movement. To counter this, the SSAO pass is often blurred to remove such grain.
 
As with traditional AO, SSAO is completely independent of the normal lighting system. This means that both the performance and appearance of the shader are unaffected by the lights used in a level.
 
The depth buffer is measured from the camera, and so SSAO is view-dependent - the size and locations of the "shadows" created by SSAO may change as the player moves the camera around. Additionally, the shading may look different along the edges of the screen - this can be combated by rendering additional information outside of the current camera's bounds.


=Enabling and Using Nvidia's Forced Driver SSAO=
==Source Filmmaker==
Nvidia's drivers feature a method that allows for SSAO to be forced on in almost any game. Enabling this feature is as simple as turning it on within Nvidia's driver control panel.
[[Source Filmmaker]] includes an SSAO option (labelled "Ambient Occlusion"), accessible by right-clicking on the viewport. The default setting is very grainy. {{todo|Adjust number of samples?}}


{{Note|Enabling Nvidia's forced SSAO can cause significant performance penalties.}}
== SSAO in the Source Engine ==
* The original release of {{dota2|4}} aswell as {{sfm|1}}, and all games on {{titanfall|4}} branch are the only {{src|4}} games and software that support SSAO.
* However, as SSAO is a post-processing effect, you can use third-party software (ReShade), or [[Source Shader Editor]] to add SSAO. Alternatively, it is possible to use the superior HBAO ambient occlusion, which can be forced through GPU driver control panel (or by using NVIDIA Profile Inspector).
{{Note|For baked Ambient Occlusion maps per model within the Source Engine, see [[$ambientocclusion]].}}
{{Note|A post process SSAO shader currently ships with the [[Source_shader_editor| Source Shader Editor]].}}
{{TODO|Write a tutorial on creating an SSAO shader and implementing it into the engine. See [[Shader Authoring]].}}
{{Note|I am currently writing a tutorial on implementing SSAO into Source Engine [http://www.moddb.com/games/lost-squad/tutorials/source-engine-implementing-simple-ssao-shader-part-1 here] (DmitRex).}}


==Supported games==
==External links==
[[{{ns:6}}:EnableAO.png|thumb|left|150px|Enabling AO in Nvidia control panel]]
*[[Wikipedia:Ambient occlusion]]
All [[Source]] engine games except [[Portal]] have driver profiles to enable Nvidia's SSAO. SSAO in Portal can be forced on by editing Portal's driver profile with an external application such as nHancer.
*[[Wikipedia:Screen Space Ambient Occlusion]]
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==Graphical Bugs==
Nvidia's SSAO implmentation was designed to be general purpose, and as such, does not take a lot of Source's stock effects into account during it's calculations. This leads to bleeding in scenes with heavy fog. As a fault of the actual SSAO shader, Ghosting and other related artifacts, pictured on the image below, can occur. It is recommended that you use a more modern SSAO implementation that takes the scene's normals into account if you intend to design your own shader for use in Source.
[[{{ns:6}}:Prop ragdoll.jpg|thumb|left|200px|SSAO in game - the shading effect is highly visible between Breen and the table, but also appears in the corners of the room. Note the edge "glow" bug around Breen's arm.]]
[[{{ns:6}}:Ao_renderbug_trees.jpg|thumb|right|200px|The shadows being rendered on top of fog are noticable on distant trees.]]

Latest revision as of 21:47, 8 February 2025

Stub

This article or section is a stub. You can help by expanding it.

Todo: Document about HBAO, alternative to SSAO which can be forced through GPU driver control panel (or NVIDIA Profile Inspector).
An example of traditional prerendered ambient occlusion in Blender 3D. SSAO attempts to mimic this look in real-time.
Note.pngNote: Not to be confused with baked ambient occlusion on models!
Todo: Expand the article to include different methods of SSAO. The method described is one of many.


Screen Space Ambient Occlusion (SSAO) works by examining an onscreen pixel, and then comparing its location in a depth buffer to the pixels around it. Pixels which are close together but not coplanar (on the same face) are shaded to simulate soft shadows. To maintain playable framerates, it is not possible to sample every pixel every frame, so random sampling is used, which will inevitably create noise/grain which may be more noticeable with movement. To counter this, the SSAO pass is often blurred to remove such grain.

As with traditional AO, SSAO is completely independent of the normal lighting system. This means that both the performance and appearance of the shader are unaffected by the lights used in a level.

The depth buffer is measured from the camera, and so SSAO is view-dependent - the size and locations of the "shadows" created by SSAO may change as the player moves the camera around. Additionally, the shading may look different along the edges of the screen - this can be combated by rendering additional information outside of the current camera's bounds.

Source Filmmaker

Source Filmmaker includes an SSAO option (labelled "Ambient Occlusion"), accessible by right-clicking on the viewport. The default setting is very grainy.

Todo: Adjust number of samples?

SSAO in the Source Engine

  • The original release of Dota 2 Dota 2 aswell as Source Filmmaker, and all games on Titanfall Titanfall branch are the only Source Source games and software that support SSAO.
  • However, as SSAO is a post-processing effect, you can use third-party software (ReShade), or Source Shader Editor to add SSAO. Alternatively, it is possible to use the superior HBAO ambient occlusion, which can be forced through GPU driver control panel (or by using NVIDIA Profile Inspector).
Note.pngNote:For baked Ambient Occlusion maps per model within the Source Engine, see $ambientocclusion.
Note.pngNote:A post process SSAO shader currently ships with the Source Shader Editor.
Todo: Write a tutorial on creating an SSAO shader and implementing it into the engine. See Shader Authoring.
Note.pngNote:I am currently writing a tutorial on implementing SSAO into Source Engine here (DmitRex).

External links

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