Improved Ray Casting of Procedural Distance Bounds

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Journal of Graphics Tools, 17 (4): 127-138 (2015)
DOI: 10.1080/2165347X.2015.1033069


In this article, we present performance and quality enhancements for ray casting procedural distance bounds using sphere tracing: First, we propose a safe overrelaxation method for accelerating the tracing process and evaluate different variants of the algorithm. Second, we introduce a technique for preventing self-intersections, which enables controlling the precision and rendering performance. In addition, we show a method for significant acceleration of the intersection test when sphere tracing convex objects. We further present a screen-space metric for retrieval of intersection point candidates, in case sphere tracing does not converge. Thereby, we allow for an increase of the rendering quality without sacrificing performance. Further, we reduce common discontinuity artifacts in sphere tracing using a fixed-point iteration algorithm. The algorithms depicted in this article are universally applicable beyond rendering complex procedurally generated scenes in real time. We demonstrate this by integrating our methods into a global illumination path-tracer.



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