Advanced animation framework for virtual character within the MPEG-4 standard

The paper presents an advanced animation framework for virtual characters within the MPEG-4 standard. The bone-based animation (BBA) specifications are described and it is shown how they extend the MPEG-4 face and body animation (FBA) specifications. Specifically, the scene graph concept, the BBA nodes related to bone and muscle modeling, the animation parameters and the compression capabilities are successively addressed and discussed within a specific application related to a sign language communication system.

1. INTRODUCTION

Virtual character (VC) animation is a well-known issue in 3D related applications, especially because of the desire to use human being-like avatars in virtual or hybrid environments. Contributing to the MPEG-4 standard Version 2, the activities of the Synthetic and Natural Hybrid Coding (SNHC) Group [11] address the animation of human avatars - so-called Face and Body Animation (FBA) - by specifying 1) the avatar modeling representation, and 2) the animation parameter representation and compression. With Similar objectives in term of low-bitrate streamed animation, the SNHC group has currently adopted the specifications of the so-called Bone-based Animation (BBA) framework [18] making it possible to realistically animate any kind of articulated VC. Animation Framework eXtension (AFX) extends the 3D· related technologies of MPEG-4 Version 2 and addresses new ones such as subdivision surfaces, volume representation, view dependent texture and mesh transmission.