Bidirectional reflection functions from surface bump maps
SIGGRAPH '87 Proceedings of the 14th annual conference on Computer graphics and interactive techniques
A global illumination solution for general reflectance distributions
Proceedings of the 18th annual conference on Computer graphics and interactive techniques
A rapid hierarchical radiosity algorithm
Proceedings of the 18th annual conference on Computer graphics and interactive techniques
Discontinuity Meshing for Accurate Radiosity
IEEE Computer Graphics and Applications
On the form factor between two polygons
SIGGRAPH '93 Proceedings of the 20th annual conference on Computer graphics and interactive techniques
The irradiance Jacobian for partially occluded polyhedral sources
SIGGRAPH '94 Proceedings of the 21st annual conference on Computer graphics and interactive techniques
A ray tracing solution for diffuse interreflection
SIGGRAPH '88 Proceedings of the 15th annual conference on Computer graphics and interactive techniques
Handbook of Mathematical Functions, With Formulas, Graphs, and Mathematical Tables,
Handbook of Mathematical Functions, With Formulas, Graphs, and Mathematical Tables,
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Computing the light field due to an area light source remains an interesting problem in computer graphics. This paper presents a series approximation of the light field due to an unoccluded area source, by expanding the light field in spherical harmonics. The source can be nonuniform and need not be a planar polygon. The resulting formulas give expressions whose cost and accuracy can be chosen between the exact and expensive Lambertian solution for a diffuse polygon, and the fast but inexact method of replacing the area source by a point source of equal power. The formulas break the computation of the light vector into two phases: The first phase represents the light source's shape and brightness with numerical coefficients, and the second uses these coefficients to compute the light field at arbitrary locations. We examine the accuracy of the formulas for spherical and rectangular Lambertian sources, and apply them to obtaining light gradients. We also show how to use the formulas to estimate light from uniform polygonal sources, sources with polynomially varying radiosity, and luminous textures.