381 research outputs found

    Interactive inspection of complex multi-object industrial assemblies

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    The final publication is available at Springer via http://dx.doi.org/10.1016/j.cad.2016.06.005The use of virtual prototypes and digital models containing thousands of individual objects is commonplace in complex industrial applications like the cooperative design of huge ships. Designers are interested in selecting and editing specific sets of objects during the interactive inspection sessions. This is however not supported by standard visualization systems for huge models. In this paper we discuss in detail the concept of rendering front in multiresolution trees, their properties and the algorithms that construct the hierarchy and efficiently render it, applied to very complex CAD models, so that the model structure and the identities of objects are preserved. We also propose an algorithm for the interactive inspection of huge models which uses a rendering budget and supports selection of individual objects and sets of objects, displacement of the selected objects and real-time collision detection during these displacements. Our solution–based on the analysis of several existing view-dependent visualization schemes–uses a Hybrid Multiresolution Tree that mixes layers of exact geometry, simplified models and impostors, together with a time-critical, view-dependent algorithm and a Constrained Front. The algorithm has been successfully tested in real industrial environments; the models involved are presented and discussed in the paper.Peer ReviewedPostprint (author's final draft

    A hybrid representation for modeling, interactive editing, and real-time visualization of terrains with volumetric features

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    Cataloged from PDF version of article.Terrain rendering is a crucial part of many real-time applications. The easiest way to process and visualize terrain data in real time is to constrain the terrain model in several ways. This decreases the amount of data to be processed and the amount of processing power needed, but at the cost of expressivity and the ability to create complex terrains. The most popular terrain representation is a regular 2D grid, where the vertices are displaced in a third dimension by a displacement map, called a heightmap. This is the simplest way to represent terrain, and although it allows fast processing, it cannot model terrains with volumetric features. Volumetric approaches sample the 3D space by subdividing it into a 3D grid and represent the terrain as occupied voxels. They can represent volumetric features but they require computationally intensive algorithms for rendering, and their memory requirements are high. We propose a novel representation that combines the voxel and heightmap approaches, and is expressive enough to allow creating terrains with caves, overhangs, cliffs, and arches, and efficient enough to allow terrain editing, deformations, and rendering in real time

    BSP-fields: An Exact Representation of Polygonal Objects by Differentiable Scalar Fields Based on Binary Space Partitioning

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    The problem considered in this work is to find a dimension independent algorithm for the generation of signed scalar fields exactly representing polygonal objects and satisfying the following requirements: the defining real function takes zero value exactly at the polygonal object boundary; no extra zero-value isosurfaces should be generated; C1 continuity of the function in the entire domain. The proposed algorithms are based on the binary space partitioning (BSP) of the object by the planes passing through the polygonal faces and are independent of the object genus, the number of disjoint components, and holes in the initial polygonal mesh. Several extensions to the basic algorithm are proposed to satisfy the selected optimization criteria. The generated BSP-fields allow for applying techniques of the function-based modeling to already existing legacy objects from CAD and computer animation areas, which is illustrated by several examples

    Parallel Mesh Processing

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    Die aktuelle Forschung im Bereich der Computergrafik versucht den zunehmenden AnsprĂŒchen der Anwender gerecht zu werden und erzeugt immer realistischer wirkende Bilder. Dementsprechend werden die Szenen und Verfahren, die zur Darstellung der Bilder genutzt werden, immer komplexer. So eine Entwicklung ist unweigerlich mit der Steigerung der erforderlichen Rechenleistung verbunden, da die Modelle, aus denen eine Szene besteht, aus Milliarden von Polygonen bestehen können und in Echtzeit dargestellt werden mĂŒssen. Die realistische Bilddarstellung ruht auf drei SĂ€ulen: Modelle, Materialien und Beleuchtung. Heutzutage gibt es einige Verfahren fĂŒr effiziente und realistische Approximation der globalen Beleuchtung. Genauso existieren Algorithmen zur Erstellung von realistischen Materialien. Es gibt zwar auch Verfahren fĂŒr das Rendering von Modellen in Echtzeit, diese funktionieren aber meist nur fĂŒr Szenen mittlerer KomplexitĂ€t und scheitern bei sehr komplexen Szenen. Die Modelle bilden die Grundlage einer Szene; deren Optimierung hat unmittelbare Auswirkungen auf die Effizienz der Verfahren zur Materialdarstellung und Beleuchtung, so dass erst eine optimierte ModellreprĂ€sentation eine Echtzeitdarstellung ermöglicht. Viele der in der Computergrafik verwendeten Modelle werden mit Hilfe der Dreiecksnetze reprĂ€sentiert. Das darin enthaltende Datenvolumen ist enorm, um letztlich den Detailreichtum der jeweiligen Objekte darstellen bzw. den wachsenden RealitĂ€tsanspruch bewĂ€ltigen zu können. Das Rendern von komplexen, aus Millionen von Dreiecken bestehenden Modellen stellt selbst fĂŒr moderne Grafikkarten eine große Herausforderung dar. Daher ist es insbesondere fĂŒr die Echtzeitsimulationen notwendig, effiziente Algorithmen zu entwickeln. Solche Algorithmen sollten einerseits Visibility Culling1, Level-of-Detail, (LOD), Out-of-Core Speicherverwaltung und Kompression unterstĂŒtzen. Anderseits sollte diese Optimierung sehr effizient arbeiten, um das Rendering nicht noch zusĂ€tzlich zu behindern. Dies erfordert die Entwicklung paralleler Verfahren, die in der Lage sind, die enorme Datenflut effizient zu verarbeiten. Der Kernbeitrag dieser Arbeit sind neuartige Algorithmen und Datenstrukturen, die speziell fĂŒr eine effiziente parallele Datenverarbeitung entwickelt wurden und in der Lage sind sehr komplexe Modelle und Szenen in Echtzeit darzustellen, sowie zu modellieren. Diese Algorithmen arbeiten in zwei Phasen: ZunĂ€chst wird in einer Offline-Phase die Datenstruktur erzeugt und fĂŒr parallele Verarbeitung optimiert. Die optimierte Datenstruktur wird dann in der zweiten Phase fĂŒr das Echtzeitrendering verwendet. Ein weiterer Beitrag dieser Arbeit ist ein Algorithmus, welcher in der Lage ist, einen sehr realistisch wirkenden Planeten prozedural zu generieren und in Echtzeit zu rendern

    Procedural 3D Caves, Clouds and Architecture Generation Method Based on Shape Grammar and Morphing

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    This paper presents a new procedural 3D modelconstructionalgorithm that benefits from a combination ofdiscrete and continuous modeling approaches. Our algorithmmodels complex scene components such as caves, architecturalbuildings, and clouds. The method combines the discretedescriptiveness of shape grammars with the continuous flexibilityof shape morphing. This combination allows for a modelingapproach that can be controlled by a morphing parameter toproduce various types of geometry. In the paper, we focus on thedescription of the algorithm while also showing its capabilities ingenerating complex scene components

    Multiresolution Techniques for Real–Time Visualization of Urban Environments and Terrains

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    In recent times we are witnessing a steep increase in the availability of data coming from real–life environments. Nowadays, virtually everyone connected to the Internet may have instant access to a tremendous amount of data coming from satellite elevation maps, airborne time-of-flight scanners and digital cameras, street–level photographs and even cadastral maps. As for other, more traditional types of media such as pictures and videos, users of digital exploration softwares expect commodity hardware to exhibit good performance for interactive purposes, regardless of the dataset size. In this thesis we propose novel solutions to the problem of rendering large terrain and urban models on commodity platforms, both for local and remote exploration. Our solutions build on the concept of multiresolution representation, where alternative representations of the same data with different accuracy are used to selectively distribute the computational power, and consequently the visual accuracy, where it is more needed on the base of the user’s point of view. In particular, we will introduce an efficient multiresolution data compression technique for planar and spherical surfaces applied to terrain datasets which is able to handle huge amount of information at a planetary scale. We will also describe a novel data structure for compact storage and rendering of urban entities such as buildings to allow real–time exploration of cityscapes from a remote online repository. Moreover, we will show how recent technologies can be exploited to transparently integrate virtual exploration and general computer graphics techniques with web applications

    Hierarchical processing, editing and rendering of acquired geometry

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    La reprĂ©sentation des surfaces du monde rĂ©el dans la mĂ©moire d’une machine peut dĂ©sormais ĂȘtre obtenue automatiquement via divers pĂ©riphĂ©riques de capture tels que les scanners 3D. Ces nouvelles sources de donnĂ©es, prĂ©cises et rapides, amplifient de plusieurs ordres de grandeur la rĂ©solution des surfaces 3D, apportant un niveau de prĂ©cision Ă©levĂ© pour les applications nĂ©cessitant des modĂšles numĂ©riques de surfaces telles que la conception assistĂ©e par ordinateur, la simulation physique, la rĂ©alitĂ© virtuelle, l’imagerie mĂ©dicale, l’architecture, l’étude archĂ©ologique, les effets spĂ©ciaux, l’animation ou bien encore les jeux video. Malheureusement, la richesse de la gĂ©omĂ©trie produite par ces mĂ©thodes induit une grande, voire gigantesque masse de donnĂ©es Ă  traiter, nĂ©cessitant de nouvelles structures de donnĂ©es et de nouveaux algorithmes capables de passer Ă  l’échelle d’objets pouvant atteindre le milliard d’échantillons. Dans cette thĂšse, je propose des solutions performantes en temps et en espace aux problĂšmes de la modĂ©lisation, du traitement gĂ©omĂ©trique, de l’édition intĂ©ractive et de la visualisation de ces surfaces 3D complexes. La mĂ©thodologie adoptĂ©e pendant l’élaboration transverse de ces nouveaux algorithmes est articulĂ©e autour de 4 Ă©lĂ©ments clĂ©s : une approche hiĂ©rarchique systĂ©matique, une rĂ©duction locale de la dimension des problĂšmes, un principe d’échantillonage-reconstruction et une indĂ©pendance Ă  l’énumĂ©ration explicite des relations topologiques aussi appelĂ©e approche basĂ©e-points. En pratique, ce manuscrit propose un certain nombre de contributions, parmi lesquelles : une nouvelle structure hiĂ©rarchique hybride de partitionnement, l’Arbre Volume-Surface (VS-Tree) ainsi que de nouveaux algorithmes de simplification et de reconstruction ; un systĂšme d’édition intĂ©ractive de grands objets ; un noyau temps-rĂ©el de synthĂšse gĂ©omĂ©trique par raffinement et une structure multi-rĂ©solution offrant un rendu efficace de grands objets. Ces structures, algorithmes et systĂšmes forment une chaĂźne capable de traiter les objets en provenance du pipeline d’acquisition, qu’ils soient reprĂ©sentĂ©s par des nuages de points ou des maillages, possiblement non 2-variĂ©tĂ©s. Les solutions obtenues ont Ă©tĂ© appliquĂ©es avec succĂšs aux donnĂ©es issues des divers domaines d’application prĂ©citĂ©s.Digital representations of real-world surfaces can now be obtained automatically using various acquisition devices such as 3D scanners and stereo camera systems. These new fast and accurate data sources increase 3D surface resolution by several orders of magnitude, borrowing higher precision to applications which require digital surfaces. All major computer graphics applications can take benefit of this automatic modeling process, including: computer-aided design, physical simulation, virtual reality, medical imaging, architecture, archaeological study, special effects, computer animation and video games. Unfortunately, the richness of the geometry produced by these media comes at the price of a large, possibility gigantic, amount of data which requires new efficient data structures and algorithms offering scalability for processing such objects. This thesis proposes time and space efficient solutions for modeling, editing and rendering such complex surfaces, solving these problems with new algorithms sharing 4 fundamental elements: a systematic hierarchical approach, a local dimension reduction, a sampling-reconstruction paradigm and a pointbased basis. Basically, this manuscript proposes several contributions, including: a new hierarchical space subdivision structure, the Volume-Surface Tree, for geometry processing such as simplification and reconstruction; a streaming system featuring new algorithms for interactive editing of large objects, an appearancepreserving multiresolution structure for efficient rendering of large point-based surfaces, and a generic kernel for real-time geometry synthesis by refinement. These elements form a pipeline able to process acquired geometry, either represented by point clouds or non-manifold meshes. Effective results have been successfully obtained with data coming from the various applications mentioned
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