Summary: Shading and Shadowing with Linear Light Sources
Pierre Pouliny and John Amanatidesz
yImager, zDepartment of Computer Science
Department of Computer Science, York University
University of British Columbia, 4700 Keele St.
Vancouver, British Columbia North York, Ontario
Canada V6T 1W5 Canada M3J 1P3
604 228-2218 416 736-5053
In virtually all rendering systems, linear light sources are modeled with a series of point
light sources that require considerable computing resources to produce realistic looking
results. A general solution for shading surfaces illuminated by a linear light source is
proposed. A formulation allowing for faster computation of the di use component of
light re ection is derived. By assuming Phong's specular component, simple, inexpen-
sive and convincing results are produced with the use of a Chebyshev approximation.
A shadowing algorithm is also presented. As shadowing from linear light sources is
expensive, two acceleration schemes, extended from ray tracing, are evaluated.
One of the requirements for generating realistic images is the capability of simulating a wide variety
of light sources. Small changes in the intensity patterns of these illuminants can signi cantly e ect