Browsing by Author "Jevans, David"

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    ADAPTIVE VOXEL SUBDIVISION FOR RAY TRACING
    (1988-11-01) Jevans, David; Wyvill, Brian
    Although regular subdivision has been shown to be efficient at ray tracing scenes where objects are evenly distributed, such algorithms perform poorly when objects are concentrated in a small number of voxels. In this paper, a method is presented where voxels in a regular grid are examined and recursively subdivided depending on object density. This integration of regular and adaptive spatial subdivision methods allows images consisting of large regularly distributed objects and small dense objects to be ray traced efficiently. The parameters controlling the coarseness of the voxel grid, depth of adaptive subdivision trees, and maximum number of polygons per voxel are varied and their effects on execution time, subdivision time, and memory use are measured.
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    RAY TRACING IMPLICIT SURFACES
    (1988-01-01) Wyvill, Brian; Jevans, David
    We present an algorithm for ray tracing implicit surfaces. The algorithm first divides space uniformly and areas of interest are adaptively subdivided using an octree method. We review earlier work on reducing intersection calculations in ray tracing and introduce a new data structure, a variation on the octree, that is more efficient in both time and memory requirements. Our results indicate that using this hybrid algorithm retains the benefits of both uniform and octree subdivision while providing better average performance than using either one of these approaches alone.