## A Fast Shadow Algorithm for Area Light Sources Using Backprojection (1994)

Citations: | 103 - 12 self |

### BibTeX

@INPROCEEDINGS{Drettakis94afast,

author = {George Drettakis and Eugene Fiume},

title = {A Fast Shadow Algorithm for Area Light Sources Using Backprojection},

booktitle = {},

year = {1994},

pages = {223--230},

publisher = {ACM SIGGRAPH, ACM Press}

}

### Years of Citing Articles

### OpenURL

### Abstract

The fast identification of shadow regions due to area light sources is necessary for realistic rendering and for discontinuity meshing for global illumination. A new shadow-determination algorithm is presented that uses a data structure, called a backprojection, to represent the visible portion of a light source from any point in the scene. A complete discontinuity meshing algorithm is described for polyhedral scenes and area light sources, which includes an important class of light/geometry interactions that have not been implemented before. A fast incremental algorithm for computing backprojections is also described. The use of spatial subdivision, and heuristics based on computed statistics of typical scenes, results in efficient mesh and backprojection computation. Results of the implementation show that the use of the backprojection and discontinuity meshing permits accelerated high-quality rendering of shadows using both ray-casting and polygon-rendering with interpolants. CR C...

### Citations

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Citation Context ... to compute images with exact radiance values in the penumbra cheaply and view-independently. These images are useful as a reference to evaluate the quality of approximations such as those in [LiTG92]=-=[Dret94a]-=-. Incremental backprojection is generally so fast that high-quality rendering is achieved even when using interpolation, at speeds competitive with previous lowerquality interpolatory approaches. A co... |

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Citation Context ...e groups are then calculated (see Figure 10(a)). The remaining regular regions of unoccluded illumination are assigned tensor product interpolants of appropriate degree, using the method described in =-=[DrFi93]-=-. The remaining penumbral faces and the light regions not in the tensor product domains, are assigned triangular quadratic interpolants (see Figure 10(b)). Rendering is performed by either querying th... |

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Mathematical Elements for Computer Graphics," (2nd Edition
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1 | Eihchiro Nakamae, "Half Tone Representation of 3-D Objects Illumination By Area Source or Polyhedron Sources - Nishita - 1983 |