Luminaire sampling plays an important role in global illumination
calculation using Monte Carlo integration. A conventional approach generates
samples on the surface of the luminaire, resulting in rendered images with high
variance of noise. In this paper, we present an efficient solid angle sampling
technique using tunable bounding volumes for global illumination calculation.
In contrast to the conventional approach, our technique derives samples from
the solid angle subtended by the luminaire. In the construction process, we
build a convex, frustum-like polyhedron as a bounding volume for a light
source. Front-facing polygons of the bounding volume are then projected onto
the unit hemisphere around the shaded point. These projected polygons represent
the approximated solid angle subtended by the luminaire. The third step
samples the projected spherical polygons on which a number of stratified samples
are generated. We employ various types of light sources including ellipse,
elliptic cylinder, elliptic cone and elliptic paraboloid. We perform our technique
for Monte Carlo Direct Lighting and Monte Carlo Path Tracing applications.
Under similar sample numbers, our technique produces images with less variance
of noise compared to the conventional method. In addition, our technique
provides roughly equal image quality in less execution time. Our approach is
simple, efficient, and applicable to many types of luminaries for global illumination
calculation.
