Rendering at Warp Speed.(Technology Information)

A new rendering architecture casts an image-based technique in silicon

Image-based rendering is becoming an increasingly popular method for generating virtual interactive representations of natural scenes quickly and efficiently. Rather than building models from scratch using geometric primitives, image-based techniques use information such as depth and color gleaned from photographs to describe complex 3D environments. But for the many applications that stand to benefit from an image-based approach--specifically those attempting to offer interactive experiences in photorealistic settings--the limitations of today's graphics hardware are a significant obstacle.

Because of this, researchers at the University of North Carolina at Chapel Hill are developing a rendering engine specifically suited to the image-based approach, bypassing the use of conventional graphics systems altogether.

Called the WarpEngine, the new architecture is designed to produce high-resolution image-based renderings of natural scenes at interactive rates. Developed by graphics researcher Voicu Popescu and his UNC colleagues, the system implements in hardware an image-based technique called 3D warping.

With 3D warping, pixels enhanced with depth and color information are projected, or warped, to a target image. Simply warping depth and color samples, however, does not produce a high-quality result. "The output image needs to be carefully reconstructed from the warped samples," says Popescu. Unfortunately, existing reconstruction algorithms implemented on conventional hardware are either too expensive, jeopardizing interactivity, or so imprecise that the quality of the warped images quickly degrades as the camera moves away from the original view. In contrast, the Warp Engine uses a "forward mapping" algorithm that accurately reconstructs the final image while requiring fewer mathematical operations.

The Warping Challenge

Although conventional graphics hardware can be used for image-based rendering using warping techniques, the computational demands of the technique significantly compromise performance. For example, to achieve a target resolution of 1280 by 1024, the hardware needs to process more than 150 million triangles per second in order to sustain a frame rate of 30Hz, which, says Popescu, "is outside of the capabilities of today's highest-end graphics engines."