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Raytracing Prefiltered Occlusion for Aggregate Geometry

Raytracing Prefiltered Occlusion for Aggregate Geometry. Lacewell, D., Burley, B., Boulos, S. and Shirley, P. IEEE Symposium on Interactive Raytracing, 2008. Chasing Performance. Faster hardware Faster single-ray intersection Fewer samples Importance sampling Prefiltering.

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Raytracing Prefiltered Occlusion for Aggregate Geometry

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  1. Raytracing Prefiltered Occlusion for Aggregate Geometry Lacewell, D., Burley, B., Boulos, S. and Shirley, P. IEEE Symposium on Interactive Raytracing, 2008

  2. Chasing Performance • Faster hardware • Faster single-ray intersection • Fewer samples • Importance sampling • Prefiltering

  3. Soft Shadows (2M tris) Standard, 4 rays Prefiltered, 9 rays Standard, 25 rays 112 seconds 74 seconds 704 seconds

  4. Bounding Volume Hierarchy - O(log N) ray intersection - O(N) update

  5. Early Ray Termination

  6. Early Termination (opaque boxes) Triangles Opaque boxes

  7. Bottom-up Prefiltering

  8. Bottom-Up Prefiltering

  9. Correlation Height

  10. Correlation Height

  11. Correlation Height

  12. Early Termination (opaque boxes) Triangles Opaque boxes

  13. Early Termination (prefiltered boxes) Triangles Prefiltered boxes

  14. Prefiltered (converged), 81 rays

  15. Regular, 81 rays, 3x slower

  16. Regular, 169 rays, 6x slower

  17. Variance Measurement

  18. Cost of Transparency

  19. Soft Shadows (5M tris) Standard, 9 rays Prefiltered, 9 rays Standard, 49 rays 64 seconds 87 seconds 339 seconds

  20. Ambient Occl. (3.8M triangles) Standard, 9 rays Prefiltered, 9 rays Standard, 36 rays 106 seconds 66 seconds 420 seconds

  21. When to Update? • Whenever BVH is updated • Independent of lights • No update for instances

  22. Memory Usage per Node

  23. Total Mem. Usage (GB) 3x3 Cubemap per Node

  24. Reference

  25. 3x3 Cubemap

  26. DC (average of 3x3 cubemap)

  27. DC (ortho average)

  28. Ad-hoc

  29. Reference

  30. 12x12 Cubemap

  31. DC (average of 12x12 cubemap)

  32. Conclusion • Simple to implement • Two runtime speedups: • Stop descending early • Less noise ==> Fewer rays • O(N) update • DC average often suffices

  33. Short-Term Future Work • Faster prefiltering • Quantization • Out of core scenes • Indirect diffuse

  34. Longer-Term Future Work Automatically classify geometry: • Nice mesh [Razor] • Aggregate and random [current paper] • Determine “correlation height” • Aggregate but not random [R-LOD?] • Buildings, vehicles, etc.

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