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This chapter presents direct lighting models for ray tracing with cylindrical lamps. Fluorescent lights are used for many lighting applications, such as classrooms and shopping centers, and neon lights are again becoming popular for advertising signs and cosmetic lighting. Fluorescent and neon luminaires can be modeled as diffuse emitting cylinders with associated spectral distributions. For spherical and triangular luminaires, previous research suggests a sampling based on the estimated sub-tense (solid angle) of the luminaire as a good strategy. However, for a cylinder this angle can be difficult to characterize. Therefore, an alternative approach is taken, which follows from the observation that an approximation to solid-angle-based sampling can be obtained by choosing p such that the luminaire point x′ is more likely to be generated nearer to the illuminated point x. This approach provides a reasonable approximation because x′ subtends a greater differential solid angle as it moves nearer to x. This chapter presents a method for performing the direct lighting computations for cylindrical luminaires in distribution ray tracing. It extends a previous concept that presents physically correct methods for computing the contribution of spherical and triangular luminaires.
A Collection of Practical Techniques for the Computer Graphics Programmer
V.6 – Direct Lighting Models for Ray Tracing with Cylindrical LampsKurt Zimmerman Indiana University, Bloomington, IndianaAvailable online 27 June 2014