ABSTRACT
This paper describes a fast, practical algorithm to compute the shadow boundaries in a polyhedral scene illuminated by a polygonal light source. The shadow boundaries divide the faces of the scene into regions such that the structure or “aspect” of the visible area of the light source is constant within each region. The paper also describes a fast, practical algorithm to compute the structure of the visible light source in each region. Both algorithms exploit spatial coherence and are the most efficient yet developed.
Given the structure of the visible light source in a region, queries of the form “What specific areas of the light source are visible?” can be answered almost instantly from any point in the region. This speeds up by several orders of magnitude the accurate computation of first level diffuse reflections due to an area light source. Furthermore, the shadow boundaries form a good initial decomposition of the scene for global illumination computations.
Supplemental Material
Available for Download
- 1.A. T. Campbell III and Donald Fussell. Adaptivemesh generationfor globaldiffuse illumination. Computer Graphics (SIGGRAPH '90 Proceedings), 24(4):155-164, August 1990. Google ScholarDigital Library
- 2.A. T. Campbell III and Donald Fussell. An analytic approach to illumination with area light sources. Department of Computer Sciences, University of Texas at Austin, technical report TR-91-25, August 1991. Google ScholarDigital Library
- 3.Bernard Chazelle, Herbert Edelsbrunner, Leonidas Guibas, Micha Sharir, and Jorge Stolfi. Lines in space: Combinatorics and algorithms. New York University, Courant Inst. of Math. Sc. Technical Report No. 491, (also in STOC 1989, pp. 382-393), February 1990.Google Scholar
- 4.Norman Chin and Steven Feiner. Near real-time shadow generationusing bsp trees. Computer Graphics (SIGGRAPH '89 Proceedings), 23(3):99-106, July 1989. Google ScholarDigital Library
- 5.Michael Cohen, ShenchangEric Chen, John R. Wallace, and Donald P. Greenberg. A progressive refinement approach to fast radiosity image generation. Computer Graphics (SIGGRAPH '88 Proceedings), 22(4):75-84, August 1988. Google ScholarDigital Library
- 6.Michael Cohen and Donald P. Greenberg. The hemi-cube: A radiosity solution for complex environments. Computer Graphics (SIGGRAPH '85 Proceedings), 19(3):31-40, August 1985. Google ScholarDigital Library
- 7.Franklin C. Crow. Shadow algorithms for computer graphics. Computer Graphics (SIGGRAPH '77 Proceedings), 11(2):242-248, July 1977. Google ScholarDigital Library
- 8.George Drettakis. Structured Sampling and Reconstruction of Illumination for Image Synthesis. PhD thesis, University of Toronto, January 1994. Google ScholarDigital Library
- 9.George Drettakis and Eugene Fiume. A fast shadow algorithm for area light sources using backprojections. COMPUTER GRAPHICS Proceedings, Annual Conference Series 1994, August 1994. Google ScholarDigital Library
- 10.Herbert Edelsbrunner. Algorithms in Computational Geometry. Springer-Verlag, 1987. Google ScholarDigital Library
- 11.Ziv Gigus, John Canny, and Raimund Seidel. Efficiently computingand represent-ing aspect graphs for polyhedral objects. IEEE Transactions on Pattern Analysis and Machine Intelligence, 13(6):542-551, June 1991. Google ScholarDigital Library
- 12.Ziv Gigus and Jitendra Malik. Computing the aspect graphs for line drawings of polyhedral objects. IEEE Transactions on Pattern Analysis and Machine Intelli-gence, 12(2):113-122, February 1990. Google ScholarDigital Library
- 13.Pat Hanrahan, David Salzman, and Larry Auperle. A rapid hierarchical radiosity algorithm. Computer Graphics (SIGGRAPH '91 Proceedings), 25(4):197-206, July 1991. Google ScholarDigital Library
- 14.Paul Heckbert. Discontinuitymeshing for radiosity. Third EurographicsWorkshop on Rendering, pages 203-215, May 1992.Google Scholar
- 15.Dani Lischinski, Filippo Tampieri, and Donald Greenberg. Discontinuity meshing for accurate radiosity. IEEE Computer Graphics & Applications, pages 25-39, November 1992. Google ScholarDigital Library
- 16.Dani Lischinski, Filippo Tampieri, and Donald Greenberg. Combining hierarchi-cal radiosity and discontinuity meshing. COMPUTER GRAPHICS Proceedings, Annual Conference Series 1993, pages 199-208, August 1993. Google ScholarDigital Library
- 17.M. McKenna. Worst-case optimal hidden-surface removal. ACM Trans. Graph., 6:19-28, 1987. Google ScholarDigital Library
- 18.Ketan Mulmuley. An efficient algorithm for hidden surface removal. Computer Graphics (SIGGRAPH '89 Proceedings), 23(3):379-388, July 1989. Google ScholarDigital Library
- 19.TomoyukiNishita and Eihachiro Nakamae. Half-tone representation of 3-d objects illuminated by area sources or polyhedron sources. COMPSAC'83, Proc. IEEE 7th Intl. Conf. Soft. and Appl. Conf., pages 237-242, November 1983.Google Scholar
- 20.George Salmon. A treatise on the Analytical Geometry of Three Dimensions. Longmans, Green and Co., 1912.Google Scholar
- 21.Arthur Scherk. personal communications.Google Scholar
- 22.Duncan M. Y. Sommerville. Analytical Geometry in three dimensions. Cambridge University Press, 1934.Google Scholar
- 23.A. James Stewart and Sherif Ghali. An output sensitive algorithm for the computa-tion of shadow boundaries. In Canadian Conference on ComputationalGeometry, pages 291-296, August 1993.Google Scholar
- 24.Jorge Stolfi. Oriented Projective Geometry. PhD thesis, StanfordUniversity, 1988.Google Scholar
- 25.Seth Teller. Computingthe antipenumbraof polyhedralholes. Computer Graphics (SIGGRAPH Procedings), August 1992. Google ScholarDigital Library
- 26.Seth Jared Teller. Visibility Computations in Densely Occluded Polyhedral Envi-ronments. PhD thesis, University of California at Berkeley, 1993.Google Scholar
- 27.Oswald Veblen and Wesley Young. Projective Geometry. Blaisdell Publishing Co., 1938.Google Scholar
Index Terms
- Fast computation of shadow boundaries using spatial coherence and backprojections
Recommendations
An efficient alias-free shadow algorithm for opaque and transparent objects using per-triangle shadow volumes
This paper presents a novel method for generating pixel-accurate shadows from point light-sources in real-time. The new method is able to quickly cull pixels that are not in shadow and to trivially accept large chunks of pixels thanks mainly to using ...
Interactive global illumination based on coherent surface shadow maps
GI '08: Proceedings of Graphics Interface 2008Interactive rendering of global illumination effects is a challenging problem. While precomputed radiance transfer (PRT) is able to render such effects in real time the geometry is generally assumed static. This work proposes to replace the precomputed ...
Fast, Realistic Lighting for Video Games
Global lighting effects produced by diffuse interreflections are typically simulated using global illumination methods such as radiosity or ray tracing. Although diffuse interreflections are crucial to produce realistic images, radiosity like methods ...
Comments