A Parallel Adaptive Point-Sampling Algorithm

Introduction There is an increasing commercial need for computers to quickly generate photorealistic images. Photorealistic computer graphics is the branch of com­ puter graphics concerned with the production of computer synthesized images that look, to the observer, as much like real photographs as possible. Today, computer generated photorealistic images are routinely used in the motion picture industry, in films such as Jurassic Park, Lion King, and Terminator II, in television commercials, and in medical imaging for the visualization of CAT and MRI scans. The reduction of time required to produce photorealistic images would provide two commercial benefits: (1) lowering the cost of existing uses by providing quicker turn around time and (2) opening up new application areas. For example, a CAD tool could be built to aid architects by allowing them to walk-through a building being designed. Current virtual-reality systems, that would allow this, require the generation of a new image every 1/20th of a second. Alas, today's technology can't produce a photorealistic image in 1/20th of a second. The production of photorealistic images is computationally intensive. It is not uncommon to take 30 minutes to generate a single photorealistic image. And, some photorealistic images take hours to produce. This process is com­ putationally intensive due to the complexity of visual clues that is required to be included in an image in order for it to look photorealistic. Among those visual clues that make an image look photorealistic and that can be observed in real photographs are: hidden surface elimination, shadows, reflections, refractions, surface details, depth of field, and motion blur. 1 2 INTRODUCTION Surface details are especially important to photorealism. When an ob­ server looks at a surface, such as a brick wall or an orange, the observer not only sees the colors of the surface but also the detail shadows that are caused by pits, bumps, and imperfections. These details and shadows give a sensation of realism to a computer generated image. It also take substantial time to generate this level of detail for an entire scene of objects. Photorealistic graphics provides the ability to depict an imagined scene. Photorealistic graphic systems are designed specifically to produce images of imagined scenes that are similar to those found in the real world. In ad­ dition, the techniques of photorealistic graphics can be applied to scientific visualization that depict non-real world scenes. Examples of scientific visu­ alization are (1) the …