1. Camera-Aware Photon Mapping Final Project of CS6620 Byong Wu “Bernard” Chong Apr. 28, 2008

2. 08 Arch. Reading Club 2 Why did I consider this? UoU SoC http://www.youtube.com/watch?v=lOWMlzOHapQ : Photon mapping with static scene http://www.youtube.com/watch?v=lOWMlzOHapQ http://blenderartists.org/forum/showthread?t=54129 : Yafray patch on reusing a photon map http://blenderartists.org/forum/showthread?t=54129 As you can see, a photon map is unaware of camera setting.

3. 08 Arch. Reading Club 3 What is Photon Mapping? – Step 1 UoU SoC A two step process: First the photons are distributed http://www2.imm.dtu.dk/visiondag/VD03/grafisk/PhotonMaps.ppt

4. 08 Arch. Reading Club 4 What is Photon Mapping? – Step 2 UoU SoC http://www2.imm.dtu.dk/visiondag/VD03/grafisk/PhotonMaps.ppt Then the scene is rendered, and the density is found.

5. 08 Arch. Reading Club 5 My Idea – Camera Photons UoU SoC Shoot ”camera-photons” from a camera. Just like ray tracing. Make a (coarse) camera-photon map If a light photon hits near a camera-photon, it will be recorded, otherwise it will be ignored. Render with only recorded photons in the map. Therefore, it is 3-step process.

6. 08 Arch. Reading Club 6 Step 1 - Camera Photon Map Creation UoU SoC Shoot coarse set of camera-photons. And make a map. It would be like throwing sticky glue globs into the scene. This is non-transparent for now on

7. 08 Arch. Reading Club 7 Step 2 – Modified Photon Shoot UoU SoC Shoot light photons, if there isn’t a camera photon nearby, it will be discarded. Only the photons sticked to the camera-photon globs would be recorded. Red hit photon will not be stored into the photon map. Blue hit photon will be stored into the photon map.

8. 08 Arch. Reading Club 8 Step 3 – Normal Photon Map Rendering UoU SoC This will be the same step as normal photon mapping. If the globs are covered enough, there won’t be many missing photons.

9. 08 Arch. Reading Club 9 How did it perform? (extreme case) UoU SoC In the extreme case (below) it performed 69% better. Normal photon mapping used 1.8M photons Camera-aware photon mapping used 180K photons. This is the original

10. 08 Arch. Reading Club 10 How did it perform? (normal case) UoU SoC In the normal case (below) it performed 1.4% worse. Normal photon mapping used 1.21M photons Camera-aware photon mapping. This took 4m:39s. Used 1.14M photons Since we are using very simple camera-photon mapping, this area has lower resolution of camera-photons resulting color attenuation.

11. 08 Arch. Reading Club 11 Evaluation Environment UoU SoC Since it is very hard to implement a photon mapping, I asked Steve’s permission for using a open ray tracer for the final project. (I was not interested on reproducing already implemented ideas) Modeler: Blender 2.45 Ray Tracer: Yafray 0.0.9 My System: AMD 1.09GHz 1GB RAM, WinXP Pro. The implementation source code is on http://www.cs.utah.edu/~bchong/Graphics/yafray0.0.9-camera- aware.zip http://www.cs.utah.edu/~bchong/Graphics/yafray0.0.9-camera- aware.zip

12. 08 Arch. Reading Club 12 Future Work I – Make it two step again. UoU SoC If the camera photons are finely shot and if it remembers which pixel it belongs to, we could just use camera-photon instead of light-based photon. If a light-based photon hits a camera photon, it will add its color to the camera-photon. After step 2 of photon shoot, the color added camera photons will be shrunken down to a image in O(N) complexity. If this is possible, even adding 2G photons would not increase required memory resource.

13. 08 Arch. Reading Club 13 Future Work II – Shoot camera photons wisely. UoU SoC Unlike light photons, camera photons could be shot and placed in manipulated manner. (If we direct a light photon’s direction, the picture might have a biased look.) Put more camera-photons in the area where we could miss necessary light-photons. On this work, I had to find the best camera-photon radius and the resolution. The software should find the optimal coefficients.

14. 08 Arch. Reading Club 14 Future Work III – Increase Camera Photon Search Speed UoU SoC If the number of camera photons increases, just checking if there is a camera photon nearby is very expensive. This would be O(search_latency * light photon bounces) This is why we should also consider Future Work I, on work I, we don’t have to check if there is a light photon on some 3D point.

15. 08 Arch. Reading Club 15 End of the Presentation Questions? UoU SoC