US Patent 7515151 Generating images using sub-domain photon maps

Computer graphics apparatus, methods, systems and program products (the term “programs” can include a product consisting of computer-readable program instructions encoded on a computer readable medium) are operable to generate pixel values for pixels in an image, and store or display a human-perceptible image based on the pixel values, using a selected ray-tracing methodology in which simulated rays are shot from the pixel into a scene, the simulated rays representing paths of simulated photons, the pixel value being representative of a point in a scene as recorded on an image plane of a simulated camera. The computer graphics system comprises a subdomain generator, a subdomain photon evaluator, an area value generator and a radiance value generator. An associated computer system generates, based on the pixel values, a display-controlling electrical output operable to control a display element and enable the display element to display an image.