MultiResolution ScreenSpace Ambient Occlusion ThaiDuong Hoang KokLim Low
Multi-Resolution Screen-Space Ambient Occlusion Thai-Duong Hoang Kok-Lim Low National University of Singapore 1
Ambient Occlusion (AO) 2
AO Cosine-weighted fraction of a tangent hemisphere that is occluded 3
Screen-Space AO (SSAO) Volumetric AO [SKUT 10] 4
SSAO (Dis)Advantages Inaccurate Local AO Over/underestimated AO Low quality Simple Fast General Easy to integrate Noise Blur 5
Multi-Resolution AO (MSSAO) Intuition 6
Multi-Resolution AO (MSSAO) Intuition 256 x 256 512 x 512 1024 x 1024 7
MSSAO Overview Geometry g-buffer (1024 x 1024) Downsample AO buffer (256 x 256) Compute AO (256 x 256) g-buffer (256 x 256) Compute AO (512 x 512) g-buffer (512 x 512) Compute AO (1024 x 1024) g-buffer (1024 x 1024) Blur & Upsample AO buffer (512 x 512) Blur & Upsample AO buffer (1024 x 1024) 8
MSSAO AO from Multiple Resolutions 9
MSSAO Overview Geometry g-buffer (1024 x 1024) Downsample AO buffer (256 x 256) Compute AO (256 x 256) g-buffer (256 x 256) Compute AO (512 x 512) g-buffer (512 x 512) Compute AO (1024 x 1024) g-buffer (1024 x 1024) Blur & Upsample AO buffer (512 x 512) Blur & Upsample AO buffer (1024 x 1024) 10
MSSAO Downsampling 11
MSSAO Overview Geometry g-buffer (1024 x 1024) Downsample AO buffer (256 x 256) Compute AO (256 x 256) g-buffer (256 x 256) Compute AO (512 x 512) g-buffer (512 x 512) Compute AO (1024 x 1024) g-buffer (1024 x 1024) Blur & Upsample AO buffer (512 x 512) Blur & Upsample AO buffer (1024 x 1024) 12
MSSAO Neighborhood Sampling 1024 x 1024 512 x 512 16 -point Poisson disk 256 x 256 Works well with a 3 x 3 Gaussian filter 13
MSSAO Computing AO • Low-variance Cheap Biased 14
MSSAO Overview Geometry g-buffer (1024 x 1024) Downsample AO buffer (256 x 256) Compute AO (256 x 256) g-buffer (256 x 256) Compute AO (512 x 512) g-buffer (512 x 512) Compute AO (1024 x 1024) g-buffer (1024 x 1024) Blur & Upsample AO buffer (512 x 512) Blur & Upsample AO buffer (1024 x 1024) 15
MSSAO Bilateral Upsampling • 16
MSSAO Combining AO Values • 17
MSSAO Temporal Filtering 18
Results Quality Blizzard [FM 08] MSSAO 19
Results Quality HBAO [BSD 08] MSSAO 20
Results Quality VAO [SKUT 10] MSSAO 21
Results Ground-truth Comparison Blender MSSAO 22
Results Noise/Blur Blizzard [FM 08] HBAO [BSD 08] MSSAO 23
Results Multiple AO Scales Small AO radius Large AO radius MSSAO 24
Results Performance • Scenes rendered at 1024 x 1024 on Ge. Force GTX 460 M • Exclusive of geometry pass • The same parameters used to produce the shown images Sibenik Cathedral Conference Room Sponza Atrium MSSAO 21. 9 ms VAO 22. 9 Blizzard 25. 7 HBAO 50. 1 24. 0 ms 24. 8 24. 9 49. 5 22. 2 ms 24. 0 28. 9 54. 3 25
MSSAO Conclusions Inaccurate Local AO Over/underestimated AO Low quality Noise Blur Use more memory Poor temporal coherence on very thin geometry Simple Fast General Easy to integrate Capture multiple shadow frequencies Not too noticeable Errors due to the use of coarse resolutions Not too noticeable unless compared with ground-truths 26
Results Additional Results 27
Results Additional Results 28
Results Additional Results 29
Results Additional Results 30
Thank You 31
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