1. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Soft Shadows using Hardware Cameras Kyle Moore COMP 870

2. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 2 Previous Work Cone Tracing ♦ Amanatides, J. 1984. Ray tracing with cones. In Proceedings of the 11th Annual Conference on Computer Graphics and interactive Techniques H. Christiansen, Ed. SIGGRAPH '84. ACM Press, New York, NY, 129- 135. ♦ Uses cones shaped rays instead of lines to calculate light intersections with objects ♦ Lots of difficult computations

3. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 3 Previous Work Forward Hardware-Based Techniques ♦ Assarsson, U. and Akenine-Möller, T. 2003. A geometry-based soft shadow volume algorithm using graphics hardware. ACM Trans. Graph. 22, 3 (Jul. 2003), 511-520. ♦ Uses silhouette edges to case penumbra volumes which are to create shadow maps ♦ This is an approximation and can be inaccurate

4. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 4 Previous Work Backwards silhouette edge detection ♦ Laine, S., Aila, T., Assarsson, U., Lehtinen, J., and Akenine-Möller, T. 2005. Soft shadow volumes for ray tracing. ACM Trans. Graph. 24, 3 (Jul. 2005), 1156-1165. ♦ Uses a hemicube acceleration structure to find silhouette edges to calculate the amount of light occlusion ♦ Doesn’t take advantage of hardware

5. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 5 My idea My Inspiration ♦ While working on my ray tracer ♦ Unhappy with soft shadows ♦ Wanted to shoot more rays, but high cost New approach ♦ Let graphics hardware simulate shooting many rays ♦ Perhaps get performance increase as well as quality enhancement

6. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 6 My Approach Area Light Source Occluder Surface Hardware Camera View Frustum Camera’s View Average Pixels to get Occlusion percentage

7. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 7 My Approach Area Light Source Occluder Surface Camera’s View

8. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 8 My Application

9. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 9 Results - Quality Old approach 4x4 grid My Approach 4x4 grid

10. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 10 Results - Quality Old approach 17x17 grid My Approach 17x17 grid

11. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 11 Results - Performance Old approach 17x17 grid 152 seconds My Approach 32x32 grid 96 seconds

12. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 12 Performance RaysCamera naive Camera w/ small optimizations 4x4 42 secs151 secs 17x17 152 secs158 secs 32x32 447 secs160 secs96 secs 64x64 181 secs 128x128 241 secs

13. The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 13 Room for improvement Each pixel draws a frame and the fetches the results Feedback loops are slow in hardware Does not take advantage of parallelization of using CPU and GPU at the same time