Screen Space Ambient Occlusion (SSAO): Difference between revisions
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{{TODO|Re-write entire article. Description of AO is inaccurate and incorrect in many places.}}<br> | {{TODO|Re-write entire article. Description of AO is inaccurate and incorrect in many places.}}<br> | ||
'''Ambient Occlusion (AO)''' is a type of [[lighting]] technique applied in-game to create more realistic lighting. AO | '''Ambient Occlusion (AO)''' is a type of [[lighting]] technique applied in-game to create more realistic lighting. AO mimics aspects of global ambient lighting, creating soft shadows between surfaces that are close together. AO can be rendered in real-time through '''[[Wikipedia:Screen Space Ambient Occlusion|Screen Space Ambient Occlusion (SSAO)]]''', a shading method which is able to closely simulate the effects of real AO with little loss of performance. | ||
SSAO works by examining an onscreen pixel, and then comparing its location in the 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 Gaussian blurred to remove such grain. | SSAO works by examining an onscreen pixel, and then comparing its location in the 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 Gaussian blurred to remove such grain. | ||
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. | |||
== SSAO in the Source Engine == | == SSAO in the Source Engine == | ||
Revision as of 01:40, 11 January 2011
Ambient Occlusion (AO) is a type of lighting technique applied in-game to create more realistic lighting. AO mimics aspects of global ambient lighting, creating soft shadows between surfaces that are close together. AO can be rendered in real-time through Screen Space Ambient Occlusion (SSAO), a shading method which is able to closely simulate the effects of real AO with little loss of performance.
SSAO works by examining an onscreen pixel, and then comparing its location in the 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 Gaussian blurred to remove such grain.
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.
SSAO in the Source Engine
Note:For faked Ambient Occlusion per model within the Source Engine, see $ambientocclusion.