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| GI'98 Online Papers |
Ray-Tracing Procedural Displacement Shaders
Abstract
Displacement maps and procedural displacement shaders are a widely
used approach of specifying geometric detail and increasing the
visual complexity of a scene.
While it is relatively straightforward to handle displacement shaders
in pipeline based rendering systems such as the
Reyes-architecture, it is much harder to
efficiently integrate displacement-mapped surfaces in ray-tracers. Many
commercial ray-tracers tessellate the surface into a multitude of small
triangles. This introduces a series of problems such as excessive
memory consumption and possibly undetected surface detail.
In this paper we describe a novel way of ray-tracing procedural
displacement shaders directly, that is, without introducing intermediate
geometry. Affine arithmetic is used to compute bounding boxes for the
shader over any range in the parameter domain. The method is comparable
to the direct ray-tracing of Bézier surfaces and implicit surfaces using
Bézier clipping and interval methods, respectively.
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