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Now showing 1 - 10 of 12
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    Procedural Texture Preview
    (The Eurographics Association and John Wiley and Sons Ltd., 2012) Lasram, Anass; Lefebvre, Sylvain; Damez, Cyrille; P. Cignoni and T. Ertl
    Procedural textures usually require spending time testing parameters to realize the diversity of appearances. This paper introduces the idea of a procedural texture preview: A single static image summarizing in a limited pixel space the appearances produced by a given procedure. Unlike grids of thumbnails our previews present a continuous image of appearances, analog to a map. The main challenge is to ensure that most appearances are visible, are allocated a similar pixel area, and are ordered in a smooth manner throughout the preview. To reach this goal, we introduce a new layout algorithm accounting simultaneously for these criteria. After computing a layout of appearances, we rely on by-example texture synthesis to produce the final preview. We demonstrate our approach on a database of production-level procedural textures.
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    From 3D Models to 3D Prints: An Overview of the Processing Pipeline
    (The Eurographics Association and John Wiley & Sons Ltd., 2017) Livesu, Marco; Ellero, Stefano; Martínez, Jonàs; Lefebvre, Sylvain; Attene, Marco; Victor Ostromoukov and Matthias Zwicker
    Due to the wide diffusion of 3D printing technologies, geometric algorithms for Additive Manufacturing are being invented at an impressive speed. Each single step along the processing pipeline that prepares the 3D model for fabrication can now count on dozens of methods, that analyse and optimize geometry and machine instructions for various objectives. This report provides a classification of this huge state of the art, and elicits the relation between each single algorithm and a list of desirable objectives during model preparation - a process globally refereed to as Process Planning. The objectives themselves are listed and discussed, along with possible needs for tradeoffs. Additive Manufacturing technologies are broadly categorized to explicitly relate classes of devices and supported features. Finally, this report offers an analysis of the state of the art while discussing open and challenging problems from both an academic and an industrial perspective.
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    Clean Color: Improving Multi-filament 3D Prints
    (The Eurographics Association and John Wiley and Sons Ltd., 2014) Hergel, Jean; Lefebvre, Sylvain; B. Levy and J. Kautz
    Fused Filament Fabrication is an additive manufacturing process by which a 3D object is created from plastic filament. The filament is pushed through a hot nozzle where it melts. The nozzle deposits plastic layer after layer to create the final object. This process has been popularized by the RepRap community. Several printers feature multiple extruders, allowing objects to be formed from multiple materials or colors. The extruders are mounted side by side on the printer carriage. However, the print quality suffers when objects with color patterns are printed a disappointment for designers interested in 3D printing their colored digital models. The most severe issue is the oozing of plastic from the idle extruders: Plastics of different colors bleed onto each other giving the surface a smudged aspect, excess strings oozing from the extruder deposit on the surface, and holes appear due to this missing plastic. Fixing this issue is difficult: increasing the printing speed reduces oozing but also degrades surface quality on large prints the required speed level become impractical. Adding a physical mechanism increases cost and print time as extruders travel to a cleaning station. Instead, we rely on software and exploit degrees of freedom of the printing process. We introduce three techniques that complement each other in improving the print quality significantly. We first reduce the impact of oozing plastic by choosing a better azimuth angle for the printed part. We build a disposable rampart in close proximity of the part, giving the extruders the opportunity to wipe oozing strings and refill with hot plastic. We finally introduce a toolpath planner avoiding and hiding most of the defects due to oozing, and seamlessly integrating the rampart. We demonstrate our technique on several challenging multiple color prints, and show that our tool path planner improves the surface finish of single color prints as well.
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    Structure-Preserving Reshape for Textured Architectural Scenes
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Cabral, Marcio; Lefebvre, Sylvain; Dachsbacher, Carsten; Drettakis, George
    Modeling large architectural environments is a difficult task due to the intricate nature of these models and the complex dependencies between the structures represented. Moreover, textures are an essential part of architectural models. While the number of geometric primitives is usually relatively low (i.e., many walls are at surfaces), textures actually contain many detailed architectural elements.We present an approach for modeling architectural scenes by reshaping and combining existing textured models, where the manipulation of the geometry and texture are tightly coupled. For geometry, preserving angles such as oor orientation or vertical walls is of key importance. We thus allow the user to interactively modify lengths of edges, while constraining angles. Our texture reshaping solution introduces a measure of directional autosimilarity to focus stretching in areas of stochastic content and to preserve details in such areas.We show results on several challenging models, and show two applications: Building complex road structures from simple initial pieces and creating complex game-levels from an existing game based on pre-existing model pieces.
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    Interactive Modeling of Support-free Shapes for Fabrication
    (The Eurographics Association, 2016) Reiner, Tim; Lefebvre, Sylvain; T. Bashford-Rogers and L. P. Santos
    We introduce an interactive sculpting approach that enables modeling of support-free objects: objects which do not require any support structures during 3D printing. We propose three operators - trim, preserve, grow - to maintain the support-free property during interactive modeling. These operators let us define brushes that perform either in an unconstrained manner (adapting the shape to the brush effect), or selectively discard changes inside the brush volume. Our technique can be applied to many modeling operations and we demonstrate it on brushes for adding or removing matter. We describe an efficient implementation of a voxel-based modeling tool that produces only support-free shapes, and show example shapes modeled within minutes.
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    Scented Sliders for Procedural Textures
    (The Eurographics Association, 2012) Lasram, Anass; Lefebvre, Sylvain; Damez, Cyrille; Carlos Andujar and Enrico Puppo
    Procedural textures often expose a set of parameters controlling their final appearance. This lets end users tune the final look and feel, typically through a set of sliders. However, it is difficult to predict the changes introduced by a given slider, especially as sliders interact in non–trivial ways. We augment the sliders controlling parameters with visual previews revealing the changes that will be introduced upon manipulation. These previews are constantly refreshed to reflect changes with respect to the current settings. The main challenge is to generate the visual sliders in a very limited pixel space and at an interactive rate. This is done by synthesizing the visual slider from a small set of patches ordered in accordance with the slider. These patches are chosen so as to reveal as much as possible the visual variations induced by the slider. The selection and ordering are achieved by using the seam–carving algorithm to carve patches with low visual impact. The obtained patches are then stitched together using patch-based texture synthesis to form the final visual slider.
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    State of the Art in Example-based Texture Synthesis
    (The Eurographics Association, 2009) Wie, Li-Yi; Lefebvre, Sylvain; Kwatra, Vivek; Turk, Greg; M. Pauly and G. Greiner
    Recent years have witnessed significant progress in example-based texture synthesis algorithms. Given an example texture, these methods produce a larger texture that is tailored to the user s needs. In this state-of-the-art report, we aim to achieve three goals: (1) provide a tutorial that is easy to follow for readers who are not already familiar with the subject, (2) make a comprehensive survey and comparisons of different methods, and (3) sketch a vision for future work that can help motivate and guide readers that are interested in texture synthesis research. We cover fundamental algorithms as well as extensions and applications of texture synthesis.
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    Iterative Carving for Self-supporting 3D Printed Cavities
    (The Eurographics Association, 2018) Hornus, Samuel; Lefebvre, Sylvain; Diamanti, Olga and Vaxman, Amir
    Additive manufacturing technologies fabricate objects layer by layer, adding material on top of already solidified layers. A key challenge is to ensure that there is always material below, for otherwise added material simply falls under the effect of gravity. This is a critical issue with most technologies, and with fused filament in particular. In this work we investigate how to compute as large as possible empty cavities which boundaries are self-supporting. Our technique is based on an iterated carving algorithm, that is fast to compute and produces nested sets of inner walls. The walls have exactly the minimal printable thickness of the manufacturing process everywhere. Remarkably, our technique is out-of-core, sweeping through the model from the top down. Using our approach, we can print large objects using as little as a single filament thickness for the boundary, providing one order of magnitude reduction in print time and material use while guaranteeing printability.
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    Topology Optimization for Computational Fabrication
    (The Eurographics Association, 2017) Wu, Jun; Aage, Niels; Lefebvre, Sylvain; Wang, Charlie; Adrien Bousseau and Diego Gutierrez
    Additive manufacturing (AM) and topology optimization (TO) form a pair of complementary techniques in transforming digital models into physical replicas: AM enables a cost-effective fabrication of geometrically complex shapes, while TO provides a powerful design methodology for generating optimized models, which are typically complex from a geometric perspective. The potential of both techniques has recently been explored in graphics, resulting in fantastic applications especially regarding structural and aesthetic properties of fabricated models. In this tutorial, we start from the fundamentals of AM and TO, and proceed to advanced TO techniques which steer the optimization process, i.e., taking into account the manufacturing as well as aesthetic appearance.
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    By-example Synthesis of Curvilinear Structured Patterns
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Zhou, Shizhe; Lasram, Anass; Lefebvre, Sylvain; I. Navazo, P. Poulin
    Many algorithms in Computer Graphics require to synthesize a pattern along a curve. This is for instance the case with line stylization, to decorate objects with elaborate patterns (chains, laces, scratches), or to synthesize curvilinear features such as mountain ridges, rivers or roads. We describe a simple yet effective method for this problem. Our method addresses the main challenge of maintaining the continuity of the pattern while following the curve. It allows some freedom to the synthesized pattern: It may locally diverge from the curve so as to allow for a more natural global result. This also lets the pattern escape areas of overlaps or fold-overs. This makes our method particularly well suited to structured, detailed patterns following complex curves. Our synthesizer copies tilted pieces of the exemplar along the curve, following its orientation. The result is optimized through a shortest path search, with dynamic programming. We speed up the process by an efficient parallel implementation. Finally, since discontinuities may always remain we propose an optional post-processing step optimally deforming neighboring pieces to smooth the transitions.