1. Approximate Ray-Tracing on the GPU with Distance Impostors László Szirmay-Kalos Barnabás Aszódi István Lazányi Mátyás Premecz TU Budapest, Hungary

2. GPU rendering versus Ray-Tracing Inremental rendering on the GPU Non-coherent Ray tracing

3. Previous work Ray-tracing on the GPU Ray-tracing on the GPU –Ray-engine (Carr et. al): Bad complexity: time  rays  triangles Bad complexity: time  rays  triangles –Regular grid (Purcell et. al): Problematic for dynamic objects Problematic for dynamic objects Environment mapping (Blinn) Environment mapping (Blinn) –Environment is at infinity –Localization with simple proxy geometry (Bjorke)

4. Contribution of this paper GPU friendly approximate ray tracing algorithm for casting incoherent rays needed, for example, when computing GPU friendly approximate ray tracing algorithm for casting incoherent rays needed, for example, when computing –Reflections –Refractions –Caustics –…

5. distance radiance Distance Impostors

6. Ray-Tracing with Distance Impostors

7. Approximation

8. Approximation Error 1 iteration 4 iterations8 iterations

9. Reflections radiance

10. Problems of environment map based reflections Environment mapReference

11. Localized Reflections distance radiance

12. Comparison of Localized Refrections

13. Refractions radiance environment

14. Multiple Localized Refractions distance normals environment

15. Comparison of Multiple Refractions

16. Multiple refraction results 109 FPS

17. Caustics distance texture u, v texture uv, power

18. 32 x 32 Texture modulation Texture uv of photon positions Vertex shader Billboard positions filter Pixel shader Lit texture or Light map 256 x 256

19. Caustics Results: 180 FPS

20. Application: Ray-tracing effects in games

21. Conclusions Distance impostors to represent geometry in ray tracing Distance impostors to represent geometry in ray tracing Iterative ray tracing algorithm Iterative ray tracing algorithm Applications (100+ FPS): Applications (100+ FPS): –Localized reflections –Single and multiple localized refractions –Caustics