Scene Based Graphics Rendering

  

In the pursuit of photo realism in conventional polygon based computer graphics, models have become so complex that most of the polygons are smaller than one pixel in the final image. At the same time, graphics hardware systems at the very high end are becoming capable of rendering, at interactive rates, nearly as many triangles per frame as there are pixels on the screen. Formerly, when models were simple and the triangle primitives were large, the ability to specify large, connected regions with only three points was a considerable efficiency in storage and computation. Now that models contain nearly as many primitives as pixels in the final image, we should rethink the use of geometric primitives to describe complex environments.

An alternative approach is being investigated that represents complex 3D environments with sets of images. These images include information describing the depth of each pixel along with the colour and other properties. Algorithms have been developed for processing these depth enhanced images to produce new images from viewpoints that were not included in the original image set. Thus, using a finite set of source images, it is now possible to produce new images from arbitrary viewpoints.

The potential impact of using images to represent complex 3D environments includes:

Naturally photo-realistic rendering, because the source data are photos. This will allow immersive 3D environments to be constructed for real places, enabling a new class of applications in entertainment, virtual tourism, telemedicine, telecollaboration, and teleoperation.

Computation proportional to the number of output pixels rather than to the number of geometric primitives as in conventional graphics. This should allow implementation of systems that produce high quality, 3D imagery with much less hardware than used in the current high performance graphics systems.

A hybrid with a conventional graphics system. A process called post rendering warping allows the rendering rate and latency to be decoupled from the user's changing viewpoint. Just as the frame buffer decoupled screen refresh from image update, post-rendering warping decouples image update from viewpoint update. This approach will enable immersive 3D systems to be implemented over long distance networks and broadcast media , using inexpensive image warpers to interface to the network and to increase interactivity.

Design of current graphics hardware has been driven entirely by the processing demands of conventional triangle based graphics. It is possible that very simple hardware may allow for real-time rendering using this new paradigm. It should be possible to write software only implementations that produce photo realistic renderings at much higher rates than with conventional graphics primitives.

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