Reflection from Layered Surfaces due to Subsurface Scattering
Report ID: TR-409-93Author: Krueger, Wolfgang / Hanrahan, Pat
Date: 1993-01-00
Pages: 32
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Abstract:
The reflection of light from most materials consists of two major terms: the specular and the diffuse. Specular reflection may be modeled from first principles by considering a rough surface consisting of perfect reflectors, or micro-facets. Diffuse reflection is generally considered to result from subsurface scattering; that is, light enters a surface layer, is scattered multiple times, and then exits in a random direction in the process inheriting the color of the surface. Accounting for diffuse reflection by Lambert's cosine law, as is universally done in computer graphics, is not a physical theory based on first principles. This paper presents a model for subsurface scattering in layered surfaces in terms of one-dimensional linear transport theory. The solutions to this equation account for diffuse reflection from first principles. This model is particularly appropriate for common layered materials appearing in nature, such as biological tissues (e.g. skin, leaves, etc.) or inorganic materials (e.g. snow, sand, paint, varnished or dusty surfaces). As an application of the model, we simulate the appearance of a face and a cluster of leaves, from experimental data describing their layer properties.