The physical mechanisms and physiological causes of glare in human vision are reviewed. These mechanisms are scattering in the cornea, lens, and retina, and diffraction in the coherent cell structures on the outer radial areas of the lens. This scattering and diffraction are responsible for the "bloom" and "flare lines" seen around very bright objects. The diffraction effects cause the "lenticular halo". The quantitative models of these glare effects are reviewed, and an algorithm for using these models to add glare effects to digital images is presented. The resulting digital point-spread function is thus psychophysically based and can substantially increase the "perceived" dynamic range of computer simulations containing light sources. Finally, a perceptual test is presented that indicates these added glare effects increase the apparent brightness of light sources in digital images.
In a distributed ray tracer, the sampling strategy is the crucial part of the direct lighting calculation. Monte Carlo integration with importance sampling is used to carry out this calculation. Importance sampling involves the design of integrand-specific probability density functions that are used to generate sample points for the numerical quadrature. Probability density functions are presented that aid in the direct lighting calculation from luminaires of various simple shapes. A method for defining a probability density fimction over a set of luminaires is presentsd that allows the direct lighting calculation to be carried out with a number of sample points that is independent of the number of luminaires.
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