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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