9 results
Search Results
Now showing 1 - 9 of 9
Item Visibility Complexity of a Region in Flatland(Eurographics Association, 2000) Rigau, Jaume; Feixas, Miquel; Sbert, MateuThe aim of this paper is to study the visibility complexity of different regions in a 2D scene. Based on mutual information, which we used in our previous work to define scene complexity, we propose two measures that quantify the complexity of a region from two different points of view. The knowledge of the complexity of a region can be useful to determine how difficult it is to recompute the visibility links for an animation depending on the regions visited or to obtain the complexity of the movement of a robot. We also envisage its applicability to obtain an optimal load balancing in a parallel computation by dividing the geometry in equal complexity regions.Item View-based Shape Similarity using Mutual Information Spheres(The Eurographics Association, 2007) GarcÃa, Francisco González; Feixas, Miquel; Sbert, Mateu; Paolo Cignoni and Jiri SochorWe present a new method for computing the shape similarity between 3D polygonal models using an informationtheoretic viewpoint selection framework. Given a 3D model, a sphere of viewpoints surrounding this model is used to obtain its shape signature from the mutual information of each viewpoint. This signature represents the essence of the shape from a view-based approach. Then, in order to quantify the dissimilarity between two models, their mutual information spheres are registered by minimizing the L2 distance between them. Several experiments show the discrimination capabilities of our approach and its potential suitability for object recognition.Item Leaf Cluster Impostors for Tree Rendering with Parallax(The Eurographics Association, 2005) Garcia, Ismael; Sbert, Mateu; Szirmay-Kalos, László; John Dingliana and Fabio GanovelliThis paper presents a simple method to render complex trees on high frame rates while maintaining parallax effects. Based on the recognition that a planar impostor is accurate if the represented polygon is in its plane, we find an impostor for each of those groups of tree leaves that lie approximately in the same plane. The groups are built automatically by a clustering algorithm. Unlike billboards, these impostors are not rotated when the camera moves, thus the expected parallax effects are provided. On the other hand, clustering allows the replacement of a large number of leaves by a single semi-transparent quadrilateral, which improves rendering time considerably. Our impostors well represent the tree from any direction and provide accurate depth values, thus the method is also good for shadow computation.Item GPUGI: Global Illumination Effects on the GPU(The Eurographics Association, 2006) Szirmay-Kalos, Laszlo; Szecsi, Laszlo; Sbert, Mateu; Nadia Magnenat-Thalmann and Katja BühlerIn this tutorial we explain how global illumination rendering methods can be implemented on Shader Model 3.0 GPUs. These algorithms do not follow the conventional local illumination model of Di- rectX/OpenGL pipelines, but require global geometric or illumination information when shading a point. In addition to the theory and state of the art of these approaches, we go into the details of a few algorithms, including mirror reflections, reflactions, caustics, diffuse/glossy indirect illumination, precomputation aided global illumination for surface and volumetric models, obscurances and tone mapping, also giving their GPU implementation in HLSL or Cg language.Item Real-time Obscurances with Color Bleeding (the three cubes demo)(Eurographics Association, 2003) Méndez, Àlex; Sbert, Mateu; Catà , JordiHere we present an animation that demonstrates the power of the obscurances technique and how it can be used in a video-game context when moving objects are in the scene. Obscurances is a powerful technique that simulates diffuse illumination, i.e. radiosity, with a much lower cost. Its advantage is based in that it considers only neighbour interactions instead of considering global ones, and in being decoupled from direct illumination computation. The implementation of this technique is made on a 3D game engine that allows real-time recomputation of obscurances for moving objects. Extensions to deal with color bleeding can also be appreciated.Item Information-Theoretic Oracle Based on Kernel Smoothness for Hierarchical Radiosity(Eurographics Association, 2002) Feixas, Miquel; Rigau, Jaume; Bekaert, Philippe; Sbert, MateuOne of the main problems in the radiosity method is how to discretise the surfaces of a scene into mesh elements that allow us to accurately represent illumination. In this paper we present a robust information-theoretic refinement criterion (oracle) based on kernel smoothness for hierarchical radiosity. This oracle improves on previous ones in that at equal cost it gives a better discretisation, approaching the optimal one from an information theory point of view, and also needs less visibility computations for a similar image quality.Item Applications of Information Theory to Computer Graphics(The Eurographics Association, 2007) Sbert, Mateu; Feixas, Miquel; Rigau, Jaume; Viola, Ivan; Chover, Miguel; Karol Myszkowski and Vlastimil HavranWe present different applications of information theory to computer graphics, based on the use of the measures of entropy, mutual information, f-divergences and generalized entropies. The application areas are hierarchical radiosity, adaptive ray-tracing, selection of best viewpoints, object and scene exploration, mesh saliency, mesh simplification and scientific visualization. We also give some hints on information-theoretic applications to object recognition and image processing.Item A Pyramidal Hemisphere Subdivision Method for Monte Carlo Radiosity(Eurographics Association, 1999) Jolivet, Vincent; Plemenos, Dimitri; Sbert, MateuIn this paper we present a new method to improve Monte Carlo radiosity by sending more rays towards selected directions. More precisely, we determine regions of the scene where the distribution of the power must be done more accurately. The number of rays sent in a direction is a function of the number of patches contained in a region, a region being a pyramid defined by the centre of the shooting patch and a spherical triangle on the surface of a hemisphere surrounding the patch. Thus, the rays shot from a patch do not have all the same power. The new method allows us not only to obtain fine details much sooner and with lower cost, but also the overall efficiency is considerably increased.Item An Integral Geometry Based Method for Fast Form-Factor Computation(Blackwell Science Ltd and the Eurographics Association, 1993) Sbert, MateuMonte Carlo techniques have been widely used in rendering algorithms for local integration. For example, to compute the contribution of a patch to the luminance of another. In the present paper we propose an algorithm based on Integral geometry where Monte Carlo is applied globally. We give some results of the implementation to validate the proposition and we study the error of the technique, as well as its complexity.