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Adaptive Volumetric Shadow Maps Marco Salviy, Kiril Vidimce, Andrew Lauritzen and Aaron Lefohn

Adaptive Volumetric Shadow Maps Marco Salviy, Kiril Vidimce, Andrew Lauritzen and Aaron Lefohn. presenters: John Koutsoumpas Nick Linakis. Overview. Adaptive Volumetric Shadow Maps. Pre-existed Methods. Adaptive Volumetric Shadow Maps. Introduction. Algorithm Overview.

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Adaptive Volumetric Shadow Maps Marco Salviy, Kiril Vidimce, Andrew Lauritzen and Aaron Lefohn

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  1. Adaptive Volumetric Shadow MapsMarco Salviy, Kiril Vidimce, Andrew Lauritzen and Aaron Lefohn presenters: John Koutsoumpas Nick Linakis

  2. Overview Adaptive Volumetric Shadow Maps

  3. Pre-existed Methods Adaptive Volumetric Shadow Maps

  4. Introduction Adaptive Volumetric Shadow Maps

  5. Algorithm Overview Adaptive Volumetric Shadow Maps

  6. AVSM - Generation Light transmittance Attenuation function: light absorbed Adaptive Volumetric Shadow Maps

  7. AVSM - Generation 1 Transmittance 0 Depth Adaptive Volumetric Shadow Maps • Render the scene from the light’s viewpoint. • Insert and render a non-opaque occluder. • Record density, entry and exit points. • Insert segments representing the ray’s traversal through the particle.

  8. AVSM - Generation frame node array texel Adaptive Volumetric Shadow Maps • Store fixed-size array including nodes for each texel. • Node → (di, ti) • Adaptively place nodes • Various shadow blocker representation. • N ≥ 2

  9. AVSM - Generation 1 1 • Integrate and composite transmittance over the segment with existing values 0.6 Transmittance 0 Depth Adaptive Volumetric Shadow Maps

  10. AVSM - Compression Adaptive Volumetric Shadow Maps • Real-time lossy compression of transmittance data • Inexpensive • Small error rate • Remove the node that contributes less • Keep first and last node intact • Compression must not re-arrange node positions • Nodes can drift unpredictably • Artifacts ( black/bright shadows, temporal aliasing )

  11. AVSM - Compression Adaptive Volumetric Shadow Maps Assume linear variation to simplify are computations Compute integral variation Removing a node affects only the area of the involved trapezoids

  12. AVSM - Compression 1 Triangle area represents the Integral variation Transmittance max nodes: 5 ΔA 6 current nodes: 5 0 Depth Adaptive Volumetric Shadow Maps

  13. AVSM - Sampling T(d)= tl+(d – dl ) texel (tl , dl) (tr , dr) Adaptive Volumetric Shadow Maps • Compute overall transmittance • Find bounding nodes of shadow receiver in depth d • Bilinear filtering

  14. Evaluation 1 Transmittance 0 Depth Adaptive Volumetric Shadow Maps

  15. Adaptive Volumetric Shadow Maps

  16. Benefits - Limitations Adaptive Volumetric Shadow Maps

  17. References Adaptive Volumetric Shadow Maps Salvi M., Vidimce K., Lauritzen A., Lefohn A., Adaptive Volumetric Shadow Maps (2010) LOKOVIC T., VEACH E.: Deep shadow maps. In Proceedings of ACM SIGGRAPH 2000 (July 2000), Computer Graphics Proceedings KIM T.-Y., NEUMANN U.: Opacity shadow maps. In Rendering Techniques 2001: 12th Eurographics Workshop on Rendering (June 2001) JANSEN J., BAVOIL L.: Fourier opacity mapping. InI3D ’10: Proceedings of the 2010 Symposium on Interactive 3D Graphics and Games (Feb. 2010)

  18. AVSM Thank you for your attention! Questions? Adaptive Volumetric Shadow Maps

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