We present an approach to define shape deformations by constructing and interactively modifying C¹ continuous time-dependent divergence-free vector fields. The deformation is obtained by a path line integration of the mesh vertices. This way, the deformation is volume-preserving, free of (local and global) self-intersections, feature preserving, smoothness preserving, and local. Different modeling metaphors support the approach which is able to modify the vector field on-the-fly according to the user input. The approach works at interactive frame rates for moderate mesh sizes, and the numerical integration preserves the volume with a high accuracy.

Figure 1: The idle CAMEL becomes a boxer with the help of MOCAP data and our mesh deformation system. In this paper, we present a multigrid technique for efficiently deforming large surface and volume meshes. We show that a previous least-squares formulation for distortion minimization reduces to a Laplacian system on a general graph structure for which we derive an analytic expression. We then describe an efficient multigrid algorithm for solving the relevant equations. Here we develop novel prolongation and restriction operators used in the multigrid cycles. Combined with a simple but effective graph coarsening strategy, our algorithm can outperform other multigrid solvers and the factorization stage of direct solvers in both time and memory costs for large meshes. It is demonstrated that our solver can trade off accuracy for speed to achieve greater interactivity, which is attractive for manipulating large meshes. Our multigrid solver is particularly well suited for a mesh editing environment which does not permit extensive precomputation. Experimental evidence of these advantages is provided on a number of meshes with a wide range of size. With our mesh deformation solver, we also successfully demonstrate that visually appealing mesh animations can be generated from both motion capture data and a single base mesh even when they are inconsistent.

Figure 1: A complex model (left) consisting of 108 components is analyzed and 250 intelligent wires (in green) are extracted. Editing a few wires induces a new wire configuration (in blue) and leads to the result on the right. Man-made objects are largely dominated by a few typical features that carry special characteristics and engineered meanings. Stateof-the-art deformation tools fall short at preserving such characteristic features and global structure. We introduce iWIRES, a novel approach based on the argument that man-made models can be distilled using a few special 1D wires and their mutual relations. We hypothesize that maintaining the properties of such a small number of wires allows preserving the defining characteristics of the entire object. We introduce an analyze-and-edit approach, where prior to editing, we perform a light-weight analysis of the input shape to extract a descriptive set of wires. Analyzing the individual and mutual properties of the wires, and augmenting them with geometric attributes makes them intelligent and ready to be manipulated. Editing the object by modifying the intelligent wires leads to a powerful editing framework that retains the original design intent and object characteristics. We show numerous results of manipulation of man-made shapes using our editing technique.

We present an algorithm that generates natural and intuitive deformations via direct manipulation for a wide range of shape representations and editing scenarios. Our method builds a space deformation represented by a collection of affine transformations organized in a graph structure. One transformation is associated with each graph node and applies a deformation to the nearby space. Positional constraints are specified on the points of an embedded object. As the user manipulates the constraints, a nonlinear minimization problem is solved to find optimal values for the affine transformations. Feature preservation is encoded directly in the objective function by measuring the deviation of each transformation from a true rotation. This algorithm addresses the problem of “embedded deformation ” since it deforms space through direct manipulation of objects embedded within it, while preserving the embedded objects ’ features. We demonstrate our method by editing meshes, polygon soups, mesh animations, and animated particle systems.

Most real world objects consist of non-uniform materials; as a result, during deformation the bending and shearing are distributed non-uniformly and depend on the local stiffness of the material. In the virtual environment there are three prevalent approaches to model deformation: purely geometric, physically driven, and skeleton based. This paper proposes a new approach to model deformation that incorporates non-uniform materials into the geometric deformation framework. Our approach provides a simple and intuitive method to control the distribution of the bending and shearing throughout the model according to the local material stiffness. Thus, we are able to generate realistic looking, material-aware deformations at interactive rates. Our method works on all types of models, including models with continuous stiffness gradation and non-articulated models such as cloth. The material stiffness across the surface can be specified by the user with an intuitive paint-like interface or it can be learned from a sequence of sample deformations. 1

We present a novel multi-scale representation and acquisition method for the animation of high-resolution facial geometry and wrinkles. We first acquire a static scan of the face including reflectance data at the highest possible quality. We then augment a traditional marker-based facial motion-capture system by two synchronized video cameras to track expression wrinkles. The resulting model consists of high-resolution geometry, motion-capture data, and expression wrinkles in 2D parametric form. This combination represents the facial shape and its salient features at multiple scales. During motion synthesis the motion-capture data deforms the high-resolution geometry using a linear shell-based mesh-deformation method. The wrinkle geometry is added to the facial base mesh using nonlinear energy optimization. We present the results of our approach for performance replay as well as for wrinkle editing.

Figure 1: A clay elephant statue (left) was modeled using sketch-based implicit-surface modeling software. Then, a lapped base texture and 25 feature textures were extracted from 22 images taken with a digital camera and composited on the surface. Photography, image creation, and texture positioning was completed in under an hour. A method is described for texturing surfaces using decals, images placed on the surface using local parameterizations. Decal parameterizations are generated with a novel O(N logN) discrete approximation to the exponential map which requires only a single additional step in Dijkstra’s graph-distance algorithm. Decals are dynamically composited in an interface that addresses many limitations of previous work. Tools for image processing, deformation/feature-matching, and vector graphics are implemented using direct surface interaction. Exponential map decals can contain holes and can also be combined with conformal parameterization to reduce distortion. The exponential map approximation can be computed on any point set, including meshes and sampled implicit surfaces, and is relatively stable under resampling. The decals stick to the surface as it is interactively deformed, allowing the texture to be preserved even if the surface changes topology. These properties make exponential map decals a suitable approach for texturing animated implicit surfaces.

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Coordinates in 3D admits a quasi-conformal deformation. In (f) the result using Mean Value Coordinates is presented. Note how Green Coordinates nicely preserve the shape of the Ogre’s head. We introduce Green Coordinates for closed polyhedral cages. The coordinates are motivated by Green’s third integral identity and respect both the vertices position and faces orientation of the cage. We show that Green Coordinates lead to space deformations with a shape-preserving property. In particular, in 2D they induce conformal mappings, and extend naturally to quasi-conformal mappings in 3D. In both cases we derive closed-form expressions for the coordinates, yielding a simple and fast algorithm for cage-based space deformation. We compare the performance of Green Coordinates with those of Mean Value Coordinates and Harmonic Coordinates and show that the advantage of the shape-preserving property is not achieved at the expense of speed or simplicity. We also show that the new coordinates extend the mapping in a natural analytic manner to the exterior of the cage, allowing the employment of partial cages. 1

In this paper, we propose novel GPU accelerated algorithms for interactive point-based rendering (PBR) and high-quality shading of transparent point surfaces. By introducing the concept of deferred blending we are able to formulate the smooth point interpolation problem as an image compositing post-processing task. Consequently, our new PBR algorithm does not suffer from an extra visibilitysplatting pre-render pass, for conservative e–z-buffer visibility culling, as this is eventually performed together with the smooth point interpolation during image compositing. Moreover, this new deferred blending concept enables hardware accelerated transparent PBR with combined effects of multi-layer transparency, refraction, specular reflection, and per-fragment shading. Deferred blending is based on a separation of the point data into not self-overlapping minimal independent groups, a multi-target rendering pass and an image compositing post-processing stage. We present different grouping algorithms for off-line and on-line processing. For basic opaque surface rendering and simple transparency effects, our novel algorithm only needs a single geometry rendering pass. For high-quality transparent image synthesis one extra rendering pass is sufficient. Besides transparency, per-fragment reflective and refractive multi-layer effects (e.g. environment mapping) are supported in our algorithm.