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Multi-Resolution Screen-Space Ambient Occlusion
Thai-Duong Hoang
Kok-Lim Low
National University of Singapore
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Ambient Occlusion (AO)
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AO
Cosine-weighted fraction of a tangent hemisphere that is occluded
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Screen-Space AO (SSAO)
Volumetric AO [SKUT10]
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SSAO(Dis)Advantages
Inaccurate
Local AO
Over/underestimated AO
Low quality
Noise
Blur
Simple
Fast
General
Easy to integrate
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Multi-Resolution AO (MSSAO)Intuition
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Multi-Resolution AO (MSSAO)Intuition
1024x1024
512x512
256x256
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MSSAOOverview
Geometryg-buffer
(1024x1024)Downsample
g-buffer (512x512)
g-buffer (256x256)
Compute AO(1024x1024)
Compute AO(512x512)
Compute AO(256x256)
Blur & Upsample
g-buffer (1024x1024)
AO buffer (256x256)
AO buffer (512x512)
Blur & Upsample
AO buffer (1024x1024)
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MSSAOAO from Multiple Resolutions
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MSSAOOverview
Geometryg-buffer
(1024x1024)Downsample
g-buffer (512x512)
g-buffer (256x256)
Compute AO(1024x1024)
Compute AO(512x512)
Compute AO(256x256)
Blur & Upsample
g-buffer (1024x1024)
AO buffer (256x256)
AO buffer (512x512)
Blur & Upsample
AO buffer (1024x1024)
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MSSAODownsampling
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MSSAOOverview
Geometryg-buffer
(1024x1024)Downsample
g-buffer (512x512)
g-buffer (256x256)
Compute AO(1024x1024)
Compute AO(512x512)
Compute AO(256x256)
Blur & Upsample
g-buffer (1024x1024)
AO buffer (256x256)
AO buffer (512x512)
Blur & Upsample
AO buffer (1024x1024)
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MSSAONeighborhood Sampling
512x512256x256
Works well with a 3x3 Gaussian filter
1024x102416-point Poisson disk
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MSSAOComputing AO
Low-variance
Cheap
Biased
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MSSAOOverview
Geometryg-buffer
(1024x1024)Downsample
g-buffer (512x512)
g-buffer (256x256)
Compute AO(1024x1024)
Compute AO(512x512)
Compute AO(256x256)
Blur & Upsample
g-buffer (1024x1024)
AO buffer (256x256)
AO buffer (512x512)
Blur & Upsample
AO buffer (1024x1024)
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MSSAOBilateral Upsampling
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MSSAOCombining AO Values
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MSSAOTemporal Filtering
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ResultsQuality
Blizzard [FM08] MSSAO 19
ResultsQuality
HBAO [BSD08] MSSAO 20
ResultsQuality
VAO [SKUT10] MSSAO 21
ResultsGround-truth Comparison
22Blender MSSAO
ResultsNoise/Blur
Blizzard [FM08] HBAO [BSD08] MSSAO23
ResultsMultiple AO Scales
Small AO radius MSSAOLarge AO radius
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ResultsPerformance
MSSAO VAO Blizzard HBAO
SibenikCathedral
21.9 ms 22.9 25.7 50.1
Conference Room
24.0 ms 24.8 24.9 49.5
SponzaAtrium
22.2 ms 24.0 28.9 54.3
• Scenes rendered at 1024x1024 on GeForce GTX 460M• Exclusive of geometry pass• The same parameters used to produce the shown images
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MSSAOConclusions
InaccurateLocal AOOver/underestimated AO
Low qualityNoiseBlur
Use more memoryPoor temporal coherence on very thin geometry
Not too noticeable
Errors due to the use of coarse resolutions
Not too noticeable unless compared with ground-truths
SimpleFastGeneralEasy to integrateCapture multiple shadow frequencies
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ResultsAdditional Results
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ResultsAdditional Results
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ResultsAdditional Results
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ResultsAdditional Results
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Thank You
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