Subdivision Surfaces in Character Animation (original) (raw)

Modeling subdivision control meshes for creating cartoon faces

Proceedings International Conference on Shape Modeling and Applications, 2001

Modeling three-dimensional faces on the computer has been an interesting yet challenging problem. This paper presents a method for creating cartoon faces by using a subdivision scheme. We use set-operations for conceptual design of subdivision control meshes. To ensure the quality of the control mesh, we have eliminated high valenced extraordinary vertices since smoothness of the surface decreases with valence. In addition, we have limited the number of extraordinary vertices to eliminate ripples. We have also ensured an even structure around extraordinary vertices (The size of each quadrilateral in subdivided meshes are roughly similar). We have also developed a user-friendly interface to sculpt the control mesh. Using this interface we have been able to create a variety of cartoon faces.

Efficient substitutes for subdivision surfaces

ACM SIGGRAPH 2009 Courses on - SIGGRAPH '09, 2009

This course provides an introduction to Approximate Subdivision Surfaces, an overview of the most recent theoretical results and their implementations on the current and next-generation GPUs, and a demonstration of these techniques and their applications in the game and movie industries.

Efficient collision detection for spherical blend skinning

Computer graphics and interactive techniques in Austalasia and South East Asia, 2006

Recently, two algorithms improving the real-time simulation of ar- ticulated models in virtual environments have been published: 1) fast collision detection for linear blend skinning and 2) spherical blend skinning. Both linear and spherical blending solve the skin- ning problem of a skeletally controlled 3D model (e.g., an avatar), but only spherical blending avoids artifacts such as the candy- wrapper.

Skinning Characters using Surface Oriented Free-Form Deformations

2000

Skinning geometry effectively continues to be one of the more challenging and time consuming aspects of character setup. While anatomic and physically based approaches to skinning have been investigated, many skinned objects have no physical equivalents. Geometric approaches, which are more general and provide finer control, are thus predominantly used in the animation industry. Free-form deformations (FFD) are a powerful paradigm for the manipulation of deformable objects. Skinning objects indirectly using an FFD lattice reduces the geometric complexity that needs to be controlled by a skeleton. Many techniques have extended the original box-shaped FFD lattices to more general control lattice shapes and topologies, while preserving the notion of embedding objects within a lattice volume. This paper in contrast, proposes a surface-oriented FFD, where the space deformed by the control surface is defined by a distance function around the surface. Surface-oriented control structures bear a strong visual semblance to the geometry they deform and can be constructed from the deformable geometry automatically. They also allow localization of control lattice complexity and deformation detail, making them ideally suited to the automated skinning of characters. This approach has been successfully implemented within the Maya2.0 animation system.

Stretch it - Realistic smooth skinning

Proceedings - Computer Graphics, Imaging and Visualisation: Techniques and Applications, CGIV'06, 2006

Smooth Skinning is still the most popular method for the animation of deformable human and creature characters. It has became almost an industry standard because of its intuitiveness to use and efficiency to compute. However it suffers from a number of problems, such as the collapsing elbow and candywrapper effect. In this paper, we present a new method, which is able to solve these defects with very little extra stretching computations. The advantage of this method is its compatibility with the current animation workflow. The animator can change the skin weight any way they like and therefore it favours creativity. The aim of our method is trying to retain the realism and computational efficiency at the same time. It is suitable for situations, where real time response is necessary, like computer games. A practical implementation in the form of a Maya plug-in is created to demonstrate the viability of the method.

Locally Interpolating Subdivision Surfaces Supporting Free-Form 2D Deformations

Deformable Avatars, 2001

This paper addresses the application of free-form deformations to arbitrarily shaped 2D textured objects, solving specific problems. Based on subdivision surfaces applied in 2D, our method successfully combines the following features: fluid good-looking movement, both general global and precise local control and explicit discontinuities. Moreover we implemented an extension to the approximating subdivision scherne, providing local interpolation and accurate border control.

Efficient cloth model for dressing animated virtual people

This paper describes a fast technique for dressing virtual humans with different pieces of clothing. The garments are constructed of cutting patterns seamed around the body. The system reads a body file and a cutting pattern file and produces a new dressed body file. The method exploits a mass-spring model of cloth but applies a new velocity modification approach to overcome its super-elasticity. This results in a more realistic cloth simulation with one more control parameter -stretching threshold. Unlike existing systems, which use object-space checks for collision detection, our approach exploits an image-space interference test. Hardware graphics accelerators are used not only for generating depth maps of the body contours but also to interpolate the normal vectors of the body. Responses to collisions are resolved modifying velocities of the cloth vertices and not applying penalty forces or energy fields as in other approaches. As the results section shows the system produces realistic images and makes it possible to sew a garment around a virtual human body in about a second on a mid-range PC.

The Elastic Surface Layer Model for Animated Character Construction

Communicating with Virtual Worlds, 1993

A model is described for creating three-dimensional animated characters. In this new type of layered construction technique, called the elastic surface layer model, a simulated elastically deformable skin surface is wrapped around a traditional kinematic articulated figure. Unlike previous layered models, the skin is free to slide along the underlying surface layers constrained by reaction forces which push the surface out and spring forces which pull the surface in to the underlying layers. By tuning the parameters of the physically-based model, a variety of surface shapes and behaviors can be obtained such as more realistic-looking skin deformation at the joints, skin sliding over muscles, and dynamic effects such as squash-and-stretch and follow-through. Since the elastic model derives all of its input forces from the underlying articulated figure, the animator may specify all of the physical properties of the character once, during the initial character design process, after which a complete animation sequence can be created using a traditional skeleton animation technique. A reasonably complex character at low surface resolution can be simulated at interactive speeds so than an animator can both design the character and animate it in a completely interactive, direct-manipulation environment. Once a motion sequence has been specified, the entire simulation can be recalculated at a higher surface resolution for better visual results. An implementation on a Silicon Graphics Iris workstation is described.

Sphere-Based Modeling, Skinning, and Animation of Characters

2010

Abstract This paper describes a representation for constructing and articulating characters made out of adjacentlyplaced spheres. We discuss a hierarchical structure for storing this representation as well as techniques for animating components of the structure. Finally, we discuss an algorithm for automatically creating triangle meshes (shells) of a sphere-based hierarchy and computing its volume. We present our findings as an interactive application that allows the user to view, create, and animate an articulated creature.