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Item Refinement criteria for adaptive stochastic ray tracing of textures(Eurographics Association, 1991) van Walsum, Theo; van Nieuwenhuizen, Peter R.; Jansen, Frederik W.Adaptive stochastic ray tracing is a rendering technique that generates high-quality anti-aliased images by sampling the image in a non-regular pattern that is adaptively refined. Image refinement can be guided by image space or object space criteria. For display of textures, additional criteria that operate in texture space can be added to further improve image quality. In this paper three texture space refinement criteria are introduced. The methods minimize the chance of sampling errors at the cost of only a small amount of preprocessing and are comparable in efficiency with existing texture prefiltering methods.Item Display of Solid Models with a Multi-Processor System(Eurographics Association, 1987) Jansen, Frederik W.; Sutherland, Robert J.There is a growing need for fast high-quality display of solid objects. Recently-developed custom-VLSI hardware offers high-speed display but lacks the flexibility and processing power at the pixel level to sustain the calculations and filter operations needed for realistic reflection models, texture mapping and anti-aliasing. Multi-processor systems built with general-purpose components of relatively high capacity and moderate cost provide an alternative; they also offer higher performance than single processor systems but retain their flexibility. A CSG hidden-surface algorithm based on depth-buffering and image subdivision is presented which is suitable for use with such a multi-processor system.Item A shadow algorithm for CSG(Eurographics Association, 1990) Jansen, Frederik W.; van der Zalm, Arno N. T.An algorithm is presented for constructing shadow volumes for CSG objects. For each primitive solid, the algorithm calculates a tree of shadow volumes to model the shadows generated by the shadow-generating parts of the boundary of the primitive. The shadow of the complete CSG object is the union of these shadow trees. An implementation of the algorithm is described for a scan-line display algorithm for CSG objects with polygonal primitives.Item Adaptive Sampling of Area Light Sources in Ray Tracing Including Diffuse Interreflection(Blackwell Science Ltd and the Eurographics Association, 1992) Kok, Arjan J. F.; Jansen, Frederik W.Ray tracing algorithms that sample both the light received directly from light sources and the light received indirectly by diffuse reflection from other patches, can accurately render the global illumination in a scene and can display complex scenes with accurate shadowing. A drawback of these algorithms, however, is the high cost for sampling the direct light which is done by shadow ray testing. Although several strategies are available to reduce the number of shadow rays, still a large number of rays will be needed, in particular to sample large area light sources. An adaptive sampling strategy is proposed that reduces the number of shadow rays by using statistical information from the sampling process and by applying information from a radiosity preprocessing. A further reduction in shadow rays is obtained by applying shadow pattern coherence, i.e. reusing the adaptive sampling pattern for neighboring sampling points.Item A Pixel-Parallelhidden Surface Algorithm For Constructive Solid Geometry(The Eurographics Association, 1986) Jansen, Frederik W.; A.A.G. RequichaVLSI techniques have greatly enlarged the possibilities to design new frame buffer architectures with parallel processing capabilities down to the pixel level. For these pixel processor systems a parallel hidden surface algorithm is presented for displaying objects defined with Constructive Solid Geometry. The algorithm is based on a CSG evaluation with bitwise operations and multiple scanning of the primitives.