1. Caustics Triangles on the GPU Umenhoffer Tamás Gustavo Patow Szirmay-Kalos László

2. CGI2 2008 Caustics – Causticus – Kaustikos

3. CGI3 2008 Generation of caustic paths specular gathering specular shooting

4. CGI4 2008 Caustic generation on the GPU  Multipass synthesis (Arvo, Jensen, Shirley)  Photon tracing from the light sources: Photon map  Final gathering for the camera  Ray tracing on the GPU: How?  Ray tracing of the original geometry: Ray engine(Carr02), Regular grid (Purcell02), octree (Meseth05), kd-tree (Foley05, Popov07, Zhou08), BVH (Carr06), ray-hierarchy (Szécsi06,Roger07).  Ray tracing of the sampled geometry: Shadow map (Shah06,Wyman06), Height map (Oliveira04), Distance map, Layered Depth Image (Krüger06) or layered cube maps (Umenhoffer07)

5. CGI5 2008 distance Ray tracing on distance maps

6. CGI6 2008 Linear search (marching) R d x r = x + Rd undershoot: |r|<|r’|=distMap(r) overshoot: |r|>|r’|=distMap(r) r r’

7. CGI7 2008 Linear search (marching) d = |x||R||x||R| t 1-t R x

8. CGI8 2008 Secant search

9. CGI9 2008 Photon power distribution  Where to store photons? – neighborhood!  Object space (Purcell03), texture space(Szirmay05), ray space (Krüger06), shadow map space (Shah06),  This paper: cube map space  How to filter?  Nearest neighbor search (Jensen95, Purcell03, Zhou08), splatting (all others),  This paper: caustic triangles. rightsmalllarge

10. CGI10 2008 Photon tracing Hit location power Triangle area

11. CGI11 2008 Filtering Photon hits Vertex shader Pixel shader Triangles with dummy vertices Vertices on the cube map face Additive blending

12. CGI12 2008 Final gathering

13. CGI13 2008 Results 60 FPS (NV6800)

14. CGI14 2008 Conclusions  Caustic generation algorithm  Stores and filters photon hits in the space of the cube map used to trace rays  Good neighborhood: during filtering visibility from the caustic generator is also taken into account  Renders caustic triangles instead of splatting  No overblurring  Continuous signal automatically  caustic triangle = adaptive filter