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This paper develops an efficient, physically based shape manipulation technique. It defines a 3D model with profile curves, and uses spine curves generated from the profile curves to control the motion and global shape of 3D models. Profile and spine curves are changed into profile and spine wires by specifying proper material and geometric properties together with external forces. The underlying physics is introduced to deform profile and spine wires through the closed form solution to ordinary differential equations for axial and bending deformations. With the proposed approach, global shape changes are achieved through manipulating spine wires, and local surface details are created by deforming profile wires. A number of examples are presented to demonstrate the applications of our proposed approach in shape manipulation. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Animating an articulated 3D character requires the specification of its interior skeleton structure which defines how the skin surface is deformed during animation. Currently this task is to a large extent accomplished manually, which consumes a large amount of animators' time. This paper presents an automatic rigging method making use of a new geometry entity called the 3D silhouette. The first step is to extract a coarse 3D curve skeleton and some skeletal joints of a character. This curve skeleton is then refined with a perpendicular silhouette. According to the connectivity of the skeletal joints, the hierarchical animation skeleton is finally constructed. By avoiding complicated computation such as voxelization and pruning, this method is simple and efficient, much faster than existing methods. It proves very useful for quick animation production, with applications including games design and prototype graphical systems. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Skin sliding is the phenomenon of the skin moving over underlying layers of fat, muscle and bone. Due to the complex interconnections between these separate layers and their differing elasticity properties, it is difficult to model and expensive to compute. We present a novel method to simulate this phenomenon at real-time by remeshing the surface based on a parameter space resampling. In order to evaluate the surface parametrization, we borrow a technique from structural engineering known as the force density method (FDM)which solves for an energy minimizing form with a sparse linear system. Our method creates a realistic approximation of skin sliding in real-time, reducing texture distortions in the region of the deformation. In addition it is flexible, simple to use, and can be incorporated into any animation pipeline. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper we present a physically motivated technique for the deformation of animated characters, called the bar-net driven skinning. We use a bar-network (bar-net) as a deforming mechanism. This technique can be used similarly to a conventional skinning tool, but can also make a skin surface behave in a physically plausible manner due to the inherent physical properties of the network. A bar-net is a structure commonly used in structural engineering. Its shape depends on the structural and material properties and the forces acting upon it. Computing the rest shape of an arbitrary bar-net is a time-consuming non-linear problem. In order to speed up the computation and also for such a bar-net to be used intuitively to help computer animation, we have defined a set of properties that a desirable bar-net should satisfy. This allows a bar-net shape finding problem to be solved using linear equations. We adopt a two-layer structure for the representation of a skin surface, including a coarse mesh and a fine mesh. To deform a skin surface, we couple a bar-net to its coarse mesh, which in turn deforms the fine mesh when the coupled bar-net is deformed. The fine surface mesh can be of different forms, including Nurbs, subdivision surfaces and polygons. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The skeleton driven skinning technique is still the most popular method for animating deformable human and creature characters. Albeit an industry de facto due to its computational performance and intuitiveness, it suffers from problems like collapsing elbow and candy wrapper joint. To remedy these problems, one needs to formulate the non-linear relationship between the skeleton and the skin shape of a character properly, which however proves mathematically very challenging. Placing additional joints where the skin bends increases the sampling rate and is an ad hoc way of approximating this non-linear relationship. In this paper, we propose a method that is able to accommodate the inherent non-linear relationships between the movement of the skeleton and the skin shape. We use the so-called curve skeletons along with the joint-based skeletons to animate the skin shape. Since the deformation follows the tangent of the curve skeleton and also due to higher sampling rates received from the curve points, collapsing skin and other undesirable skin deformation problems are avoided. The curve skeleton retains the advantages of the current skeleton driven skinning. It is easy to use and allows full control over the animation process. As a further enhancement, it is also fairly simple to build realistic muscle and fat bulge effect. A practical implementation in the form of a Maya plug-in is created to demonstrate the viability of the technique. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

As skin shape depends on the underlying anatomical structure, the anatomy-based techniques usually afford greater realism than the traditional skeleton-driven approach. On the downside, however, it is against the current animation workflow, as the animator has to model many individual muscles before the final skin layer arrives, resulting in an unintuitive modelling process. In this paper, we present a new anatomy-based technique that allows the animator to start from an already modelled character. Muscles having visible influence on the skin shape at the rest pose are extracted automatically by studying the surface geometry of the skin. The extracted muscles are then used to deform the skin in areas where there exist complex deformations. The remaining skin areas, unaffected or hardly affected by the muscles, are handled by the skeleton-driven technique, allowing both techniques to play their strengths. In order for the extracted muscles to produce realistic local skin deformation during animation, muscle bulging and special movements are both represented. Whereas the former ensues volume preservation, the latter allows a muscle not only to deform along a straight path, but also to slide and bend around joints and bones, resulting in the production of sophisticated muscle movements and deformations. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]