GPU Pro 7

3. Progressive Rendering Using Multi-frame Sampling 165

mapping, the lights’ surfaces are randomly sampled: For each frame, a random

position on each of the selected lights is used for shadow map rendering as well

as scene lighting and shading. Accumulating multiple frames results in realistic

and aliasing-free soft shadows with large penumbras.

Sampling characteristics Good convergence is achieved by uniformly sampling the

surfaces of all lights. For very large area or volumetric lights, we used an approach

similar to the previously described multi-frame DoF, starting with sampling the

light in its center and slowly progressing toward its edges,