1 / 29

Efficient Simulation of Light Transport in Scenes with Participating Media using Photon Maps

This paper discusses a method for realistically rendering scenes with participating media, including effects such as multiple volume scattering, color bleeding, and volume caustics. It extends the photon mapping technique to achieve global illumination in scenes with participating media.

bellg
Download Presentation

Efficient Simulation of Light Transport in Scenes with Participating Media using Photon Maps

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Efficient Simulation of Light Transport in Scenes with Participating Media using Photon Maps- Henrik Wann JensenPer H. Christensen 05’ Digital Image Synthesis Presented by Jen-Yuan Chiang

  2. Issues addressed by the paper • Realistic Volume Rendering • The ability to simulate following effects: • Multiple Volume Scattering • Color Bleeding between volumes and surfaces • Volume Caustics

  3. Multiple Scattering • Single Scattering • Multiple Scattering

  4. Color Bleeding Without participating media With participating media

  5. Caustics • Surface Caustics Light reflected from or transmitted through one or more specular surfaces strikes a diffuse surface.

  6. Caustics • Volume Caustics Light reflected from or transmitted through specular surfaces and then scattered by a medium

  7. Issues addressed in this paper • Extends the method of photon mapping to achieve the global illumination of scenes with participating media

  8. Outline • Overview of Photon mapping for surfaces • Light transport in participating media • Extending Photon Mapping to Participating Media • Results

  9. Overview of Photon Mapping for Surfaces • Global Illumination technique • Two-pass particle-tracing algorithm • First pass: • Building the photon maps using photon tracing • Second pass: • Rendering using these photon maps

  10. First pass • Photons emitted from light sources • Simulate the transport of each photon • Store photon in photon maps when it hits nonespecular surfaces • Direct map • Caustics map • Indirect map • Balanced kd-tree is used to handle photons

  11. 3 photon maps Ex. LSSSDSSSSD Caustic map Indirect map

  12. Second Pass Specular reflection Direct Illumination Indirect illumination Caustics

  13. Second Pass • Illumination at a point is divided into four parts • Specular reflection: ray tracing • Direct illumination: direct map or ray tracing • Caustics: caustics photon map • Indirect illumination: indirect photon map

  14. Radiance Estimate • Information of Photons • Position(p), power( ), incoming direction( )

  15. Outline • Overview of Photon mapping for surfaces • Light transport in participating media • Extending Photon Mapping to Participating Media • Results

  16. Light Transport in Participating media p q Radiance L changes continuously from L(p,w) to L(q,w)

  17. Volume Scattering • Emission • In-Scattering • Absorption • Out-Scattering Scattering coefficient Absorption coefficient

  18. Volume Rendering Equation Extinction coefficient Ray marching

  19. Ray Marching • Computes the contribution from the medium by dividing the ray into smaller segments X0 X1 X2 Xk emission in-scattering extinction(assuming medium properties are the same through )

  20. Outline • Overview of Photon mapping for surfaces • Light transport in participating media • Extending Photon Mapping to Participating Media • Results

  21. Extending Photon Mapping to participating media • From for surfaces to for volumes • Still 2 pass particle tracing algorithm • First pass: • additional volume photon map • Second pass: • rendering using ray marching

  22. Volume Radiance Estimate • Estimate radiance using volume photon map

  23. Volume Radiance Estimate for Ray Marching • For each ray through the volume, we can get the radiance caused by volume scattering by marching along the ray and cumulating every in-scatteredradiance single scattering (direct):by ray tracing Multiple scattering (indirect): by volume radiance estimate

  24. Outline • Overview of Photon mapping for surfaces • Light transport in participating media • Extending Photon Mapping to Participating Media • Results

  25. Features of Volumetric Photon Mapping • Can model- • Homogeneous as well as non-homogeneous media. • Isotropic as well as anisotropic media. • Since decoupled from geometry (photons stored in kd-tree), so capable of handling complex scene.

  26. Some Results • Anisotropic and non-homogeneous medium

  27. Underwater Scene with Volume Caustics

  28. Pseudo code for volume photon mapping • http://www-graphics.stanford.edu/courses/cs348b-competition/cs348b-05/abandoned/index.html

  29. Thanks!

More Related