Start date: 2001 × Author: Alexa, Marc ×

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Now showing 1 - 10 of 11
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    crdbrd: Shape Fabrication by Sliding Planar Slices
    (The Eurographics Association and John Wiley and Sons Ltd., 2012) Hildebrand, Kristian; Bickel, Bernd; Alexa, Marc; P. Cignoni and T. Ertl
    We introduce an algorithm and representation for fabricating 3D shape abstractions using mutually intersecting planar cut-outs. The planes have prefabricated slits at their intersections and are assembled by sliding them together. Often such abstractions are used as a sculptural art form or in architecture and are colloquially called 'cardboard sculptures'. Based on an analysis of construction rules, we propose an extended binary space partitioning tree as an efficient representation of such cardboard models which allows us to quickly evaluate the feasibility of newly added planar elements. The complexity of insertion order quickly increases with the number of planar elements and manual analysis becomes intractable. We provide tools for generating cardboard sculptures with guaranteed constructibility. In combination with a simple optimization and sampling strategy for new elements, planar shape abstraction models can be designed by iteratively adding elements. As an output, we obtain a fabrication plan that can be printed or sent to a laser cutter. We demonstrate the complete process by designing and fabricating cardboard models of various well-known 3D shapes.
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    Point-Based Computer Graphics
    (Eurographics Association, 2003) Alexa, Marc; Dachsbacher, Carsten; Gross, Markus; Pauly, Mark; van Baar, Jeroen; Zwicker, Matthias
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    Steerable Texture Synthesis
    (Eurographics Association, 2004) Taponecco, Francesca; Alexa, Marc; M. Alexa and E. Galin
    Texture synthesis is typically concerned with the creation of an arbitrarily sized texture from a small sample, where the pattern of the generated texture should be perceived as resembling the example. Most of the current work follows a Markov model approach. The texture is generated by finding best matching pixels or patches in the sample and then copying them to the target. Here we extend this concept to incorporate arbitrary filters acting on the sample before matching and transferring. The filters may vary over the generated texture. Steering the filters with properties connected to the output image allows generating a variety of effects.
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    Hybrid Ambient Occlusion
    (The Eurographics Association, 2009) Reinbothe, Christoph K.; Boubekeur, Tamy; Alexa, Marc; D. Ebert and J. Krüger
    Ambient occlusion captures a subset of global illumination effects, by computing for each point of the surface the amount of incoming light from all directions and considering potential occlusion by neighboring geometry. We introduce an approach to ambient occlusion combining object and image space techniques in a deferred shading context. It is composed of three key steps: an on-the-fly voxelization of the scene, an occlusion sampling based on this voxelization and a bilateral filtering of this sampling in screen space. The result are smoothly varying ambient terms in occluded areas at interactive frame rates without any precomputation. In particular, all computations are performed dynamically on the GPU while eliminating the problem of screen-space methods, namely ignoring geometry that is not rasterized into the Z-buffer.
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    Competitive Runtime Performance for Inverse Kinematics Algorithms using Conformal Geometric Algebra
    (The Eurographics Association, 2006) Hildenbrand, Dietmar; Fontijne, Daniel; Wang, Yusheng; Alexa, Marc; Dorst, Leo; Dieter Fellner and Charles Hansen
    Conformal geometric algebra is a powerful tool to find geometrically intuitive solutions. We present an approach for the combination of compact and elegant algorithms with the generation of very efficient code based on two different optimization approaches with different advantages, one is based on Maple, the other one is based on the code generator Gaigen 2. With these results, we are convinced that conformal geometric algebra will be able to become fruitful in a great variety of applications in Computer Graphics.
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    SHADOWPIX: Multiple Images from Self Shadowing
    (The Eurographics Association and John Wiley and Sons Ltd., 2012) Bermano, Amit; Baran, Ilya; Alexa, Marc; Matusik, Wojciech; P. Cignoni and T. Ertl
    SHADOWPIX are white surfaces that display several prescribed images formed by the self-shadowing of the surface when lit from certain directions. The effect is surprising and not commonly seen in the real world. We present algorithms for constructing SHADOWPIX that allow up to four images to be embedded in a single surface. SHADOWPIX can produce a variety of unusual effects depending on the embedded images: moving the light can animate or relight the object in the image, or three colored lights may be used to produce a single colored image. SHADOWPIX are easy to manufacture using a 3D printer and we present photographs, videos, and renderings demonstrating these effects.
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    Interactive Shape Modeling
    (The Eurographics Association, 2005) Alexa, Marc; Angelidis, Alexis; Cani, Marie-Paule; Singh, Karan; Zorin, Denis; Ming Lin and Celine Loscos
    The course will present the state-of-the-art in digital modeling techniques, both in commercial software and academic research. The goal of this course is to impart the audience with an understanding of the big open questions as well as the skills to engineer recent research in interactive shape modeling applications.
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    Mesh Morphing
    (Eurographics Association, 2001) Alexa, Marc
    Meshes have become a widespread and popular representation of models in computer graphics. Morphing techniques aim at transforming a given source shape into a target shape. Morphing techniques have various applications ranging from special effects in television and movies to medical imaging and scientific visualization. Not surprisingly, morphing techniques for meshes have received a lot of interest lately. This state of the art report sums up recent developments in the area of mesh morphing. It presents a consistent framework to classify and compare various techniques approaching the same underlying problems from different angles.
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    Approximating Free-form Geometry with Height Fields for Manufacturing
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Herholz, Philipp; Matusik, Wojciech; Alexa, Marc; Olga Sorkine-Hornung and Michael Wimmer
    We consider the problem of manufacturing free-form geometry with classical manufacturing techniques, such as mold casting or 3-axis milling. We determine a set of constraints that are necessary for manufacturability and then decompose and, if necessary, deform the shape to satisfy the constraints per segment. We show that many objects can be generated from a small number of (mold-)pieces if slight deformations are acceptable. We provide examples of actual molds and the resulting manufactured objects.
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    Point Based Computer Graphics
    (Eurographics Association, 2002) Gross, Markus; Pfister, Hanspeter; Zwicker, Matthias; Pauly, Mark; Stamminger, Marc; Alexa, Marc
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