The calculation of globalillumination taking into account not only the direct light but also all its possible reflections is an important part of the synthesis of realistic images. The simulation of global illuminati...
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The calculation of globalillumination taking into account not only the direct light but also all its possible reflections is an important part of the synthesis of realistic images. The simulation of globalillumination requires a lot of computational resources. The performance of modern computers directly depends on the number of cores, which allow one to use tens of parallel computation threads. The paper is devoted to the effective use of multicore computers for simulating the globalillumination. The computation results are represented in a uniform illumination map. The proposed algorithm dynamically creates additional threads for the critical branches of the computation process or processing of results. As a result, the uniform load of computation threads as achieved, and the physical and virtual cores are fully loaded.
Point-based globalillumination (PBGI) uses a dense point sampling of the scene's surfaces to approximate indirect light transport and is intensively used in 3D motion pictures and special effects. Each point cach...
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Point-based globalillumination (PBGI) uses a dense point sampling of the scene's surfaces to approximate indirect light transport and is intensively used in 3D motion pictures and special effects. Each point caches the reflected light using a spherical function and is typically used in a subsequent rasterization process to compute color bleeding and ambient occlusion in an economic, noise-free fashion. The entire point set is organized in a spatial tree structure which models the light transport hierarchically, enabling fast adaptive shading on receivers (e.g., unprojected pixels). One of the major limitations of PBGI is related to the size of this tree, which can quickly become too large to fit in memory for complex scenes. However, we observe that, just as with natural images, this point data set is extremely redundant. In this paper, we present a new method exploiting this redundancy by factorizing PBGI data over the tree nodes. In particular, we show that a k-means clustering in the parameter space of the spherical functions allows to define a small number of representative nodes against which any new one can be classified. These representative functions, gathered in a pre-process over a subset of the actual points, form a look-up table which allows to substitute node's data by quantized integers in a streaming process, avoiding building the full tree before compressing it. Depending on the nodes' spherical function variance in the scene and the desired accuracy, our indexed PBGI representation achieves between one and two orders of magnitude compression of the nodes spherical functions, with negligible numerical and perceptual error in the final image. In the case of a binary tree with one surfel per leaf and no spherical functions in the leaves, this leads to compression rates ranging from 3x to 5x for the whole tree.
The Point-Based globalillumination (PBGI) algorithm is composed of two major steps: a caching step and a multiview rasterization step. At caching time, a dense point-sampling of the scene is shaded and organized in a...
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The Point-Based globalillumination (PBGI) algorithm is composed of two major steps: a caching step and a multiview rasterization step. At caching time, a dense point-sampling of the scene is shaded and organized in a spatial hierarchy, with internal nodes approximating the radiance of their subtrees using spherical harmonics. At rasterization time, a microbuffer is instantiated at the unprojected position of each image pixel (receiver). Then, a view-adaptive level-of-detail of the scene is extracted in the form of a tree cut and rasterized in the receiver's microbuffer, solving for visibility using a local variant of the z-buffer. Finally, the pixel color is computed by convolving its filled microbuffer with the surface BRDF. This noise-free indirect lighting method is widely used in the industry and captures several critical lighting effects, including ambient occlusion, color bleeding, (indirect) soft-shadows and environment lighting. However, we observe a large redundancy in this algorithm, both in cuts and receivers'microbuffers, which stems from their relatively low resolution. In this paper, we propose an evolution of PBGI which exploits spatial coherence to reduce these redundant computations. Starting from a similarity-based variational clustering of the receivers, we compute a single tree cut and rasterize a single microbuffer for each cluster. This per-cluster microbuffer provides a faithful approximation of the incident radiance for distant nodes and is composited over a receiver-specific microbuffer rasterizing only the closest nodes of the cluster's cut. This factorized approach is easy to integrate in any existing PBGI implementation and offers a significant rendering speed-up for a negligible and controllable approximation error.
This paper describes the 3D digital reconstruction of Sinhaya, a X-XIIth century Muslim suburb in the city of Zaragoza. Accurate models and textures were obtained that capture all the wear and tear of a real suburb po...
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This paper describes the 3D digital reconstruction of Sinhaya, a X-XIIth century Muslim suburb in the city of Zaragoza. Accurate models and textures were obtained that capture all the wear and tear of a real suburb populated by real characters. The visualization is based on archaeological evidence from excavations and accurate historical documents. Precise lighting algorithms developed by Grupo de Informatica Grafica Avanzada (GIGA) provide a photorealistic look, while real actors composited into the synthetic scenes give life to the reconstruction. Images and animations can be viewed in a low-cost CAVE-like system (CLS) designed and developed by GIGA. Following a historically accurate script, the audience is taken through the streets of the suburb and into its houses. This digital reconstruction will help to preserve part of the city's archaeological and cultural heritage, giving life to a distant past. Visitors can experience what life was like in the suburb from morning to sunset, and it can provide a new perspective for historians. (C) 2004 Published by Elsevier SAS.
Tato práce se zabývá jednou z globálních zobrazovacích metod - radiozitou. Je zde zpracována podstata metody, uvedeny základní rovnice a vztahy. Dále je zde přehl...
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Tato práce se zabývá jednou z globálních zobrazovacích metod - radiozitou. Je zde zpracována podstata metody, uvedeny základní rovnice a vztahy. Dále je zde přehled možných řešení této metody v praxi a popis konkrétní implementace založené na využití grafické karty a OpenGL. Práce si klade za cíl popsat stručně, jasně a srozumitelně základní problémy a přístupy při implementaci radiozity.
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