1. Progressive Photon Mapping 최인창(Inchang Choi) KAIST (Korea Advanced Institute of Science and Technology)

2. Intro: MC based methods • can simulate specular and diffuse material • Problems: • Caustics (LS+DE) • SDS paths (LSDSE)

3. Intro: Photon Mapping • Two pass algorithm • First pass: Photon Tracing • Second pass: Ray Tracing using the photon maps • Problem: • Scenes dominated by caustics ->We don’t have infinite memory

4. Intro: Progressive Photon Mapping • An extension of Photon Mapping • Include SDS paths with arbitrary accuracy without infinite memory • Multi-pass algorithm • First Pass: Ray Tracing • Subsequent Passes: Photon Tracing

5. Photon Mapping

6. Photon Mapping:First Pass: Photon Tracing • Shoot photons from the light source • -using MC technique and Russian Roulette • -store photons in K-d tree • Position, incident direction, flux • Manage two photon maps • Caustic map • Global photon map Caustic mapphotons Global mapphotons From John C. Hart’s ppt

7. Photon Mapping:Second Pass: Ray Tracing • Trace rays • Calculate illumination using two photon maps DA = pr2 Use the nearest N photons to estimate L at point x From John C. Hart’s ppt

8. Photon Mapping:Second Pass: Ray Tracing Direct Illumination Diffuse Indirect Illumination Specular Illumination Caustic Illumination From Michael Kaiser and Christian Finger’s ppt

9. How can it be improved? • 1. Make the number of photons very large • (lim n->∞) • Use an Iterative method • 2. Reduce the radius r • (limt r-> 0) • Reduce the radius every iteration

10. Progressive Photon Mapping

11. Progressive Photon MappingFirst Pass: Ray Tracing • Shoot a ray from eye to the scene • Trace the path until the first non-specular surface • Store the hit point if the surface has non-specular(diffuse) component in the BRDF

12. Progressive Photon MappingFirst Pass: Ray Tracing • A Hit Point Structure These are updated each subsequent passes

13. Progressive Photon MappingSubsequent Pass: Photon Tracing • In each Pass • Trace a given number of photons into the scene

14. Progressive Photon MappingSubsequent Pass: Photon Tracing • After each Pass • Loop all hit points • :Find the photons within the radius • :refine the estimate of the illumination • (Reduce R, increase N, update τ)

15. Progressive Photon MappingRadius Reduction

16. Progressive Photon MappingFlux Correction

17. Progressive Photon MappingRadiance Evaluation

18. A Video Result • http://www.youtube.com/watch?v=zg9NcCw53iA

19. Result Comparison

20. Thank you for listening • Any Questions?