Adaptation of virtual human animation and representation for MPEG

While level of detail (LoD) methods for the representation of 3D models are efficient and established tools to manage the trade-off between speed and quality of the rendering, LoD for animation has not yet been intensively studied by the community, and especially virtual humans animation has not been focused in the past. Animation, a major step for immersive and credible virtual environments, involves heavy computations and as such, it needs a control on its complexity to be embedded into real-time systems. Today, it becomes even more critical and necessary to provide such a control with the emergence of powerful new mobile devices and their increasing use for cyberworlds. With the help of suitable middleware solutions, executables are becoming more and more multi-platform. However, the adaptation of content, for various network and terminal capabilities—as well as for different user preferences, is still a key feature that needs to be investigated. It would ensure the adoption of ‘‘Multiple Target Devices Single Content’’ concept for virtual environments, and it would in theory provide the possibility of such virtual worlds in any possible condition without the need for multiple content. It is on this issue that we focus, with a particular emphasis on 3D objects and animation. This paper presents some theoretical and practical methods for adapting a virtual human’s representation and animation stream, both for their skeleton-based body animation and their deformation-based facial animation, we also discuss practical details to the integration of our methods into MPEG-21 and MPEG-4 architectures. r 2004 Elsevier Ltd. All rights reserved.