Results 1  10
of
35
Componentwise Controllers for StructurePreserving Shape Manipulation
"... Recent shape editing techniques, especially for manmade models, have gradually shifted focus from maintaining local, lowlevel geometric features to preserving structural, highlevel characteristics like symmetry and parallelism. Such new editing goals typically require a preprocessing shape analy ..."
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Cited by 19 (9 self)
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Recent shape editing techniques, especially for manmade models, have gradually shifted focus from maintaining local, lowlevel geometric features to preserving structural, highlevel characteristics like symmetry and parallelism. Such new editing goals typically require a preprocessing shape analysis step to enable subsequent shape editing. Observing that most editing of shapes involves manipulating their constituent components, we introduce componentwise controllers that are adapted to the component characteristics inferred from shape analysis. The controllers capture the natural degrees of freedom of individual components and thus provide an intuitive user interface for editing. A typical model usually results in a moderate number of controllers, allowing easy establishment of semantic relations among them by automatic shape analysis supplemented with user interaction. We propose a componentwise propagation algorithm to automatically preserve the established interrelations while maintaining the defining characteristics of individual controllers and respecting the userspecified modeling constraints. We extend these ideas to a hierarchical setup, allowing the user to adjust the tool complexity with respect to the desired modeling complexity. We demonstrate the effectiveness of our technique on a wide range of manmade models with structural features, often containing multiple connected pieces. 1.
Fast automatic skinning transformations
 ACM TRANS. GRAPH
"... Skinning transformations are a popular way to articulate shapes and characters. However, traditional animation interfaces require all of the skinning transformations to be specified explicitly, typically using a control structure (a rig). We propose a system where the user specifies only a subset ..."
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Cited by 16 (2 self)
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Skinning transformations are a popular way to articulate shapes and characters. However, traditional animation interfaces require all of the skinning transformations to be specified explicitly, typically using a control structure (a rig). We propose a system where the user specifies only a subset of the degrees of freedom and the rest are automatically inferred using nonlinear, rigidity energies. By utilizing a loworder model and reformulating our energy functions accordingly, our algorithm runs orders of magnitude faster than previous methods without compromising quality. In addition to the immediate boosts in performance for existing modeling and real time animation tools, our approach also opens the door to new modes of control: disconnected skeletons combined with shapeaware inverse kinematics. With automatically generated skinning weights, our method can also be used for fast variational shape modeling.
Spatial Deformation Transfer
, 2009
"... Much effort is invested in generating natural deformations of threedimensional shapes. Deformation transfer simplifies this process by allowing to infer deformations of a new shape from existing deformations of a similar shape. Current deformation transfer methods can be applied only to shapes whic ..."
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Cited by 9 (1 self)
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Much effort is invested in generating natural deformations of threedimensional shapes. Deformation transfer simplifies this process by allowing to infer deformations of a new shape from existing deformations of a similar shape. Current deformation transfer methods can be applied only to shapes which are represented as a single component manifold mesh, hence their applicability to reallife 3D models is somewhat limited. We propose a novel deformation transfer method, which can be applied to a variety of shape representations – tetmeshes, polygon soups and multiplecomponent meshes. Our key technique is deformation of the space in which the shape is embedded. We approximate the given source deformation by a harmonic map using a set of harmonic basis functions. Then, given a sparse set of userselected correspondence points between the source and target shapes, we generate a deformation of the target shape which has differential properties similar to those of the source deformation. Our method requires only the solution of linear systems of equations, and hence is very robust and efficient. We demonstrate its applicability on a wide range of deformations, for different shape representations.
Interactive Surface Modeling using Modal Analysis
"... We propose a framework for deformationbased surface modeling that is interactive, robust and intuitive to use. The deformations are described by a nonlinear optimization problem that models static states of elastic shapes under external forces which implement the user input. Interactive response i ..."
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Cited by 9 (5 self)
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We propose a framework for deformationbased surface modeling that is interactive, robust and intuitive to use. The deformations are described by a nonlinear optimization problem that models static states of elastic shapes under external forces which implement the user input. Interactive response is achieved by a combination of model reduction, a robust energy approximation, and an efficient quasiNewton solver. Motivated by the observation that a typical modeling session requires only a fraction of the full shape space of the underlying model, we use second and third derivatives of a deformation energy to construct a lowdimensional shape space that forms the feasible set for the optimization. Based on mesh coarsening, we propose an energy approximation scheme with adjustable approximation quality. The quasiNewton solver guarantees superlinear convergence without the need of costly Hessian evaluations during modeling. We demonstrate the effectiveness of the approach on different examples including the test suite introduced in [Botsch and Sorkine 2008].
GUIBAS L.: Mapbased exploration of intrinsic shape differences and variability
 ACM Trans. Graph
"... Figure 1: The notion of shape difference defined in this paper provides a way to compare deformations between shape pairs. This allows us to recognize similar expressions of shape A (top row) to those of shape B (bottom row), without correspondences between A and B and without any prior learning pro ..."
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Cited by 8 (1 self)
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Figure 1: The notion of shape difference defined in this paper provides a way to compare deformations between shape pairs. This allows us to recognize similar expressions of shape A (top row) to those of shape B (bottom row), without correspondences between A and B and without any prior learning process. We develop a novel formulation for the notion of shape differences, aimed at providing detailed information about the location and nature of the differences or distortions between the two shapes being compared. Our difference operator, derived from a shape map, is much more informative than just a scalar global shape similarity score, rendering it useful in a variety of applications where more refined shape comparisons are necessary. The approach is intrinsic and is based on a linear algebraic framework, allowing the use of many common linear algebra tools (e.g, SVD, PCA) for studying a matrix representation of the operator. Remarkably, the formulation allows us not only to localize shape differences on the shapes involved, but also to compare shape differences across pairs of shapes, and to analyze the variability in entire shape collections based on the differences between the shapes. Moreover, while we use a map or correspondence to define each shape difference, consistent correspondences between the shapes are not necessary for comparing shape differences, although they can be exploited if available. We give a number of applications of shape differences, including parameterizing the intrinsic variability in a shape collection, exploring shape collections using local variability at different scales, performing shape analogies, and aligning shape collections.
An Efficient Construction of Reduced Deformable Objects
"... Figure 1: Nonlinear simulation of a deformable object with 92 k tets computed at over 120 Hz after about 4 mins of preprocessing. Many efficient computational methods for physical simulation are based on model reduction. We propose new model reduction techniques for the approximation of reduced forc ..."
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Cited by 7 (4 self)
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Figure 1: Nonlinear simulation of a deformable object with 92 k tets computed at over 120 Hz after about 4 mins of preprocessing. Many efficient computational methods for physical simulation are based on model reduction. We propose new model reduction techniques for the approximation of reduced forces and for the construction of reduced shape spaces of deformable objects that accelerate the construction of a reduced dynamical system, increase the accuracy of the approximation, and simplify the implementation of model reduction. Based on the techniques, we introduce schemes for realtime simulation of deformable objects and interactive deformationbased editing of triangle or tet meshes. We demonstrate the effectiveness of the new techniques in different experiments with elastic solids and shells and compare them to alternative approaches.
Poisson Coordinates
"... Abstract—Harmonic functions are the critical points of a Dirichlet energy functional, the linear projections of conformal maps. They play an important role in computer graphics, particularly for gradientdomain image processing and shapepreserving geometric computation. We propose Poisson coordinat ..."
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Cited by 6 (0 self)
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Abstract—Harmonic functions are the critical points of a Dirichlet energy functional, the linear projections of conformal maps. They play an important role in computer graphics, particularly for gradientdomain image processing and shapepreserving geometric computation. We propose Poisson coordinates, a novel transfinite interpolation scheme based on the Poisson integral formula, as a rapid way to estimate a harmonic function on a certain domain with desired boundary values. Poisson coordinates are an extension of the Mean Value coordinates (MVCs) which inherit their linear precision, smoothness, and kernel positivity. We give explicit formulas for Poisson coordinates in both continuous and 2D discrete forms. Superior to MVCs, Poisson coordinates are proved to be pseudoharmonic (i.e., they reproduce harmonic functions on ndimensional balls). Our experimental results show that Poisson coordinates have lower Dirichlet energies than MVCs on a number of typical 2D domains (particularly convex domains). As well as presenting a formula, our approach provides useful insights for further studies on coordinatesbased interpolation and fast estimation of harmonic functions. Index Terms—Poisson integral formula, transfinite interpolation, barycentric coordinates, pseudoharmonic Ç 1
Fisheye video correction
 IEEE Transactions on Visualization and Computer Graphics
, 2011
"... Abstract—Various types of video can be captured with fisheye lenses; their wide field of view is particularly suited to surveillance video. However, fisheye lenses introduce distortion, and this changes as objects in the scene move, making fisheye video difficult to interpret. Current still fisheye ..."
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Cited by 5 (2 self)
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Abstract—Various types of video can be captured with fisheye lenses; their wide field of view is particularly suited to surveillance video. However, fisheye lenses introduce distortion, and this changes as objects in the scene move, making fisheye video difficult to interpret. Current still fisheye image correction methods are either limited to small angles of view, or are strongly content dependent, and therefore unsuitable for processing video streams. We present an efficient and robust scheme for fisheye video correction, which minimizes timevarying distortion and preserves salient content in a coherent manner. Our optimization process is controlled by user annotation, and takes into account a wide set of measures addressing different aspects of natural scene appearance. Each is represented as a quadratic term in an energy minimization problem, leading to a closedform solution via a sparse linear system. We illustrate our method with a range of examples, demonstrating coherent naturallooking video output. The visual quality of individual frames is comparable to those produced by stateoftheart methods for fisheye still photograph correction.
On reconstruction of nonrigid shapes with intrinsic regularization
"... ShapefromX is a generic type of inverse problems in computer vision, in which a shape is reconstructed from some measurements. A specially challenging setting of this problem is the case in which the reconstructed shapes are nonrigid. In this paper, we propose a framework for intrinsic regulariza ..."
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Cited by 3 (1 self)
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ShapefromX is a generic type of inverse problems in computer vision, in which a shape is reconstructed from some measurements. A specially challenging setting of this problem is the case in which the reconstructed shapes are nonrigid. In this paper, we propose a framework for intrinsic regularization of such problems. The assumption is that we have the geometric structure of a shape which is intrinsically (up to bending) similar to the one we would like to reconstruct. For that goal, we formulate a variation with respect to vertex coordinates of a triangulated mesh approximating the continuous shape. The numerical core of the proposed method is based on differentiating the fast marching update step for geodesic distance computation. 1.
WarpCurves: A Tool for Explicit Manipulation of Implicit Surfaces
, 2010
"... We introduce WarpCurves, a technique for interactively manipulating an implicit surface using curvebased spatial deformations. Although implicit surfaces have several advantages in 3D modeling, current workflows are limited by the compositional nature of implicit modeling. Wide classes of surface f ..."
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Cited by 3 (3 self)
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We introduce WarpCurves, a technique for interactively manipulating an implicit surface using curvebased spatial deformations. Although implicit surfaces have several advantages in 3D modeling, current workflows are limited by the compositional nature of implicit modeling. Wide classes of surface features that are easy to create with the direct manipulation tools available for explicit surface representations are difficult to reproduce using volumetric implicit operations. We describe a novel spatial deformation that can be used to approximate direct surface manipulation. With our method an artist first draws a curve on the current surface to indicate the feature regionofinterest. Deformations applied to this handle curve are transferred to the implicit surface via an automaticallyconstructed C² continuous space mapping. Additional curves can be added in a hierarchical manner to create complex shapes. Our technique is implemented as a node in the BlobTree hierarchical implicit volume representation, and hence can be used along with other volumetric nodes (operators) such as blending and CSG. Our results show that surface deformations which would be difficult to reproduce using existing volumetric operations can be quickly constructed using warp curves, making them a valuable addition to the implicit modeling toolbox.