Exponential shadow maps

ABSTRACT

Rendering high-quality shadows in real-time is a challenging problem. Shadow mapping has proved to be an efficient solution, as it scales well for complex scenes. However, it suffers from aliasing problems. Filtering the shadow map alleviates aliasing, but unfortunately, native hardware-accelerated filtering cannot be applied, as the shadow test has to take place beforehand.

We introduce a simple approach to shadow map filtering, by approximating the shadow test using an exponential function. This enables us to pre-filter the shadow map, which in turn allows for high quality hardware-accelerated filtering. Compared to previous filtering techniques, our technique is faster, consumes less memory and produces less artifacts.

REFERENCES

• 1: T. Aila and S. Laine. Alias-free shadow maps. In Proceedings of Eurographics Symposium on Rendering 2004, pages 161--166. Eurographics Association, 2004.
• 2: T. Annen, T. Mertens, P. Bekaert, H.-P. Seidel, and J. Kautz. Convolution shadow maps. In Rendering Techniques 2007, volume 18 of Eurographics / ACM SIGGRAPH Symposium Proceedings, pages 51--60. Eurographics, June 2007.
• 3: S. Brabec, T. Annen, and H.-P. Seidel. Practical shadow mapping. Journal of Graphics Tools, 7(4):9--18, 2003.
• 4: F. C. Crow. Shadow algorithms for computer graphics. Computer Graphics (Proceedings of SIGGRAPH '77), pages 242--248, 1977.
• 5: W. Donnelly and A. Lauritzen. Variance shadow maps. In SI3D '06: Proceedings of the 2006 symposium on Interactive 3D graphics and games, pages 161--165, New York, NY, USA, 2006. ACM Press.
• 6: R. Fernando, S. Fernandez, and K. Bala. Adaptive shadow maps. In Proceedings of SIGGRAPH '01, Computer Graphics Proceedings, Annual Conference Series, pages 387--390. ACM SIGGRAPH, 2001.
• 7: J.-M. Hasenfratz, M. Lapierre, N. Holzschuh, and F. Sillion. A survey of real-time soft shadows algorithms. Computer Graphics Forum (Proceedings of Eurographics '03), 22(3), 2003.
• 8: A. Lauritzen. Summed-Area Variance Shadow Maps. Addison-Wesley, 2007.
• 9: W. T. Reeves, D. Salesin, and R. L. Cook. Rendering antialiased shadows with depth maps. Computer Graphics (Proceedings of SIGGRAPH '87), pages 283--291, 1987.
• 10: M. Salvi. Rendering filtered shadows with exponential shadow maps. In ShaderX 6.0 - Advanced Rendering Techniques. Charles River Media, 2008.
• 11: M. Stamminger and G. Drettakis. Perspective shadow maps. ACM Transactions on Graphics (Proceedings of SIGGRAPH 2002), pages 557--562, 2002.
• 12: L. Williams. Casting curved shadows on curved surfaces. Computer Graphics (Proceedings of SIGGRAPH '78), pages 270--274, 1978.
• 13: M. Wimmer, D. Scherzer, and W. Purgathofer. Light space perspective shadow maps. In Proceedings of the 2nd EG Symposium on Rendering, Springer Computer Science. Eurographics, Eurographics Association, 2004.
• 14: A. Woo, P. Poulin, and A. Fournier. A survey of shadow algorithms. IEEE Computer Graphics & Applications, pages 13--32, 1990.

INDEX TERMS

Primary Classification:
  I. Computing Methodologies
  I.3 COMPUTER GRAPHICS
      I.3.7 Three-Dimensional Graphics and Realism

Additional Classification:
  I. Computing Methodologies
  I.3 COMPUTER GRAPHICS
      I.3.1 Hardware architecture