Fast and detailed approximate global illumination by irradiance decomposition

ABSTRACT

In this paper we present an approximate method for accelerated computation of the final gathering step in a global illumination algorithm. Our method operates by decomposing the radiance field close to surfaces into separate far- and near-field components that can be approximated individually. By computing surface shading using these approximations, instead of directly querying the global illumination solution, we have been able to obtain rendering time speed ups on the order of 10x compared to previous acceleration methods. Our approximation schemes rely mainly on the assumptions that radiance due to distant objects will exhibit low spatial and angular variation, and that the visibility between a surface and nearby surfaces can be reasonably predicted by simple location and orientation-based heuristics. Motivated by these assumptions, our far-field scheme uses scattered-data interpolation with spherical harmonics to represent spatial and angular variation, and our near-field scheme employs an aggressively simple visibility heuristic. For our test scenes, the errors introduced when our assumptions fail do not result in visually objectionable artifacts or easily noticeable deviation from a ground-truth solution. We also discuss how our near-field approximation can be used with standard local illumination algorithms to produce significantly improved images at only negligible additional cost.

References

1. Atkinson, K. E. 2000. The planar radiosity equation and its numerical solution. IMA Journal of Numerical Analysis 20, 303--332.
2. Basri, R., and Jacobs, D. 2000. Lambertian reflectance and linear subspaces. Tech. Rep. MCS00-21, 2000-172R, Waizmann Instritude of Science, NEC Research Institude.
3. Bekaert, P., Dutre, P., and Willems, Y. D. 1998. Final radiosity gather step using a monte carlo technique with optimal importance sampling. Tech. Rep. CW275.
4. Dutré, P., Bekaert, P., and Bala, K. 2003. Advanced Global Illumination. A. K. Peters Ltd.
5. Epstein, R., Hallinan, P. W., and Yuille, A. L. 1995. 5 ± 2 eigenimages suffice: An empirical investigation of low-dimensional lighting models. In IEEE workshop on physics-based modeling in computer vision, 108--116.
6. Gautron. P. Krivanek, J., Pattanaik, S., and Bouatouch, K. 2004. A novel hemispherical basis for accurate and efficient rendering. In Rendering Techniques 2004: 15th Eurographics Workshop on Rendering, 321--330.
7. Greger. G. Shirley, P. Hubbard, P. M., and Greenberg, D. P. 1998. The irradiance volume. IEEE Comput. Graph. Appl. 18. 2. 32--43.
8. Hottel, H. C., and Saforim. A. F. 1967. Radiative Transfer. McGraw Inc.
9. Jensen, H. W. 2001. Realistic Image Synthesis Using Photon Mapping. A. K. Peters, Natick. MA.
10. Krivanek, J., Gautron. P., Pattanaik, S., and Bouatouch, K. 2005. Radiance caching for efficient global illumination computation. In IEEE Transacations of Visualization and Comptuer Graphics.
11. Lischinski, D., Tampieri. F. and Greenberg, D. P. 1993. Combining hierarchical radiosity and discontinuity meshing. Computer Graphics 27, Annual Conference Series, 199--208.
12. Ramamoorthi, R., and Hanrahan, P. 2001. An efficient representation for irradiance environment maps. In SIGGRAPH 2001, Computer Graphics Proceedings, 497--500.
13. Ramamoorthi. R., and Hanrahan, P. 2001. The relationship between radiance and irradiance: Determining the illumination from images of a convex lambertian object. In Journal of the Optical Society of America.
14. Rathsfeld, A. 1999. Edge asymptotics for the radiosity equation over polyhedral boundaries. Mathematical Methods in the Applied Sciences 22, 3, 217--241.
15. Rushmeier, H. E., Patterson, C., and Veerasamy, A. 1993. Geometric simplification for indirect illumination calculations. In Graphics Interface.
16. Rushmeier, H. E. 1988. Realistic Image Synthesis for Scenes with Radiatively Participating Media. Ph. D. thesis.
17. Scheel, A., Stamminger, M., and Seidel, H. 2001. Thrifty final gather for radiosity. In Rendering Techniques 2001 (Proc. of Eurographics Workshop on Rendering 2001), Eurographics.
18. Scheel, A., Stamminger, M., and Seidel, H. P. 2002. Grid based final gather for radiosity on complex scenes. In EUROGRAPHICS 2002, 547--555.
19. Sillion, F., and Puech, C. 1994. Radiosity and Global Illumination. Morgan Kaufmann, San Francisco, CA.
20. Sloan, P. P., Kautz, J., and Snyder, J. 2002. Precomputed radiance transfer for real-time rendering in dynamic, low-frequency lighting environments. In SIGGRAPH 2002, Computer Graphics Proceedings, 527--536.
21. Tabellion, E., and Lamorlette, A. 2004. An approximate global illumination system for computer generated films. In SIGGRAPH 2004. Computer Graphics Proceedings.
22. Ward, G. J., and Heckbert, P. 1992. Irradiance Gradients. In Third Eurographics Workshop on Rendering, 85--98.
23. Ward, G., Rubinstein, F., and Clear, R. 1988. A ray tracing solution for diffuse interreflectio. In SIGGRAPH 1988, Computer Graphics Proceedings.
24. Zimmerman, K., and Shirley, P. 1995. A Two-Pass Realistic Image Synthesis Method for Complex Scenes. In Rendering Techniques '95 (Proceedings of the Sixth Eurographics Workshop on Rendering), 284--295.

Index Terms

• Computing methodologies

  • Artificial intelligence

    • Computer vision

      • Image and video acquisition

        • 3D imaging

  • Computer graphics

    • Animation

    • Image manipulation

    • Rendering