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Metropolis Light Transport for Participating Media

Metropolis Light Transport for Participating Media. Mark Pauly Thomas Kollig Alexander Keller. ETH Zürich University of Kaiserslautern. Overview. Light Transport for Participating Media Path Integral Formulation Sampling Rendering with Metropolis Light Transport Results Conclusions.

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Metropolis Light Transport for Participating Media

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  1. Metropolis Light Transport for Participating Media Mark Pauly Thomas Kollig Alexander Keller ETH Zürich University of Kaiserslautern

  2. Overview • Light Transport for Participating Media • Path Integral Formulation • Sampling • Rendering with Metropolis Light Transport • Results • Conclusions

  3. Related Work MC Methods FE Methods • Light Tracing ‘93 • Pattanaik, Mudur • Zonal Methods ‘87 • Rushmeier, Torrance • Bidirectional Path Tracing ‘96 • Lafortune, Willems • Hierarchical Radiosity ‘93 • Bhate • Photon Map ‘98 • Jensen, Christensen • Spherical Harmonics ‘84 • Kajiya, von Herzen • Metropolis Light Transport ‘97 • Veach, Guibas • Discrete Ordinates ‘94 • Languenou, Bouatouch, Chelle

  4. Light Transport • Global Balance Equation In-scattering Streaming Emission Absorption Out-scattering

  5. • Path Integral Path Integral Formulation • Measurement Equation

  6. object 0 medium 1 1 1  sensor light source • Path Characteristic

  7. • Path Space Measure  • Path Space

  8. • Path Integral • Measurement Contribution Function

  9. Equidistant Sampling  efficient  aliasing Stratified Sampling  anti-aliasing  inefficient Random Offset Sampling Sampling • Line Integral Computation: Ray Marching

  10. Metropolis Light Transport • Generate a random walk through path space • For each path deposit a constant amount of energy at the corresponding pixel • Obtain desired image by distributing paths according to image contribution •  Metropolis sampling

  11. Metropolis Sampling • Propose a mutation of current path • Compute acceptance probability • Choose as new sample if  Samples are correlated  we can exploit coherence

  12. Mutation Strategies • Bidirectional Mutations • large changes to the current path • ensures ergodicity • Perturbations • high acceptance probability • changes to image location • low cost Scattering Perturbations Propagation Perturbations Sensor Perturbations Caustic Perturbations

  13. Propagation Perturbation medium image plane light source eye

  14. Results

  15. Results

  16. Results

  17. Conclusions • Participating media are fully integrated • inhomogeneous media • multiple, anisotropic scattering • volume caustics • color bleeding • General geometry and reflection models • Robust • Complex Scenes • Difficult Lighting Situations

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