Browsing by Author "Havran, Vlastimil"

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    Optimal Deterministic Mixture Sampling
    (The Eurographics Association, 2019) Sbert, Mateu; Havran, Vlastimil; Szirmay-Kalos, László; Cignoni, Paolo and Miguel, Eder
    Multiple Importance Sampling (MIS) can combine several sampling techniques preserving their advantages. For example, we can consider different Monte Carlo rendering methods generating light path samples proportionally only to certain factors of the integrand. MIS then becomes equivalent to the application of the mixture of individual sampling densities, thus can simultaneously mimic the densities of all considered techniques. The weights of the mixture sampling depends on how many samples are generated with each particular method. This paper examines the optimal determination of this parameter. The proposed method is demonstrated with the combination of BRDF sampling and Light source sampling, and we show that it not only outperforms the application of the two individual methods, but is superior to other recent combination strategies and is close to the theoretical optimum.
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    Optimizing Ray Tracing of Trimmed NURBS Surfaces on the GPU
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Sloup, Jaroslav; Havran, Vlastimil; Zhang, Fang-Lue and Eisemann, Elmar and Singh, Karan
    The representation of geometric models by trimmed NURBS surfaces has become a standard in the CAD industry. In CAD applications, the rendering of surfaces is usually solved by tessellation followed up by z-buffer rendering. Ray tracing of NURBS surfaces has not been widely used in industry due to its computational complexity that hinders achieving real-time performance in practice. We propose novel methods achieving faster point location search needed by trimming in the context of ray tracing trimmed NURBS surfaces. The proposed 2D data structure based on kd-trees allows for faster ray tracing while it requires less memory for its representation and less preprocessing time than previously published methods. Further, we show the current state of the art for ray tracing trimmed NURBS surfaces on a GPU. With careful design and implementation, the number of rays cast on a GPU may reach real-time performance in the order of tens to hundreds of million rays per second for moderately to large complex scenes containing hundreds of thousands of NURBS surfaces and trimming curves.