Applications of Irradiance Tensors to the Simulation of Non-Lambertian Phenomena

James Arvo

Abstract

We present new techniques for computing illumination from non-diffuse luminaires and scattering from non-diffuse surfaces. The methods are based on new closed-form expressions derived using a generalization of irradiance known as irradiance tensors. The elements of these tensors are angular moments, weighted integrals of the radiation field that are useful in simulating a variety of non-diffuse phenomena. Applications include the computation of irradiance due to directionally-varying area light sources, reflections from glossy surfaces, and transmission through glossy surfaces. The principles apply to any emission, reflection, or transmission distribution expressed as a polynomial over the unit sphere. We derive expressions for a simple but versatile subclass of these functions, called axial moments, and present complete algorithms their exact evaluation in polyhedral environments. The algorithms are demonstrated by simulating Phong-like emission and scattering effects.

Bibtex Entry

    @INPROCEEDINGS{ Arvo95a,
        AUTHOR    = "James Arvo",
        TITLE     = "Applications of Irradiance Tensors to the Simulation
	             of Non-{Lambertian} Phenomena",
        BOOKTITLE = "Computer Graphics {\rm Proceedings}",
        SERIES    = "Annual Conference Series, ACM SIGGRAPH",
        YEAR      = 1995,
        PAGES     = "335--342"
        }

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