Full Papers 2013 - CGF 32-Issue 2

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https://diglib.eg.org/handle/10.2312/13885

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Browsing Full Papers 2013 - CGF 32-Issue 2 by Subject "and systems"

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    Exploring Local Modifications for Constrained Meshes
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Deng, Bailin; Bouaziz, Sofien; Deuss, Mario; Zhang, Juyong; Schwartzburg, Yuliy; Pauly, Mark; I. Navazo, P. Poulin
    Mesh editing under constraints is a challenging task with numerous applications in geometric modeling, industrial design, and architectural form finding. Recent methods support constraint-based exploration of meshes with fixed connectivity, but commonly lack local control. Because constraints are often globally coupled, a local modification by the user can have global effects on the surface, making iterative design exploration and refinement difficult. Simply fixing a local region of interest a priori is problematic, as it is not clear in advance which parts of the mesh need to be modified to obtain an aesthetically pleasing solution that satisfies all constraints. We propose a novel framework for exploring local modifications of constrained meshes. Our solution consists of three steps. First, a user specifies target positions for one or more vertices. Our algorithm computes a sparse set of displacement vectors that satisfies the constraints and yields a smooth deformation. Then we build a linear subspace to allow realtime exploration of local variations that satisfy the constraints approximately. Finally, after interactive exploration, the result is optimized to fully satisfy the set of constraints. We evaluate our framework on meshes where each face is constrained to be planar.
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    Global Selection of Stream Surfaces
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Esturo, Janick Martinez; Schulze, Maik; Rössl, Christian; Theisel, Holger; I. Navazo, P. Poulin
    Stream surfaces are well-known and widely-used structures for 3D flow visualization. A single surface can be sufficient to represent important global flow characteristics. Unfortunately, due to the huge space of possible stream surfaces, finding the globally most representative stream surface turns out to be a hard task that is usually performed by time-consuming manual trial and error exploration using slight modifications of seed geometries. To assist users we propose a new stream surface selection method that acts as an automatic preprocessing step before data analysis. We measure stream surface relevance by a novel surface-based quality measure that prefers surfaces where the flow is aligned with principal curvature directions. The problem of seed structure selection can then be reduced to the computation of simple minimal paths in a weighted graph spanning the domain. We apply a simulated annealing-based optimization method to find smooth seed curves of globally near-optimal stream surfaces. We illustrate the effectiveness of our method on a series of synthetic and real-world data sets.