a b s t r a c tDue to its intrinsic complexity, full-body postural input has been mostly limited to off-line motion capture and to on-line puppetry of a virtual character with little interaction with its environment (e.g. floor). The motion capture technology is now mature enough to envision the on-line full-body postural control of virtual mannequins involved in precise reaching tasks. We have investigated such tasks for mannequins of differing body heights in comparison to that of the system user. Such broad-range avatar control is relevant for virtual prototyping in various industrial sectors as a single person is responsible for evaluating a virtual prototype for a full range of potential end-users. In the present paper we report on two scaling strategies that can be enforced in such a context of height-differing avatar control. Both scaling strategies have been evaluated in a wide-range reach study both in front of a stationary immersive display and with an HMD. A comparison is also made with a baseline scenario, which exploits a simple rigid shape (i.e. a proxy), to assess the specific influence of controlling a complex articulated avatar.

No abstract

Transjugular intrahepatic portosystemic shunt formation (TIPS) is an effective treatment for portal hypertension [LaBerge 1995]. The procedure requires the insertion of a needle through the liver to connect the hepatic and portal veins. This operation is traditionally guided by fluoroscopic images that do not show the location of the target veins during needle insertion. We propose to provide the clinician an interactive, three-dimensional (3D), stereo display so that the position and orientation of the clinician's needle can be seen relative to the target vasculature intraoperatively. This paper describes the visualizations we are providing for intraoperative guidance.

No abstract

Interactive control of a virtual character through full body movement has a wide range of applications. However, there is a need for systems that accurately reproduce the motion of a performer while accounting for surrounding obstacles. We propose an approach based on a Prioritized Inverse Kinematics constraint solver. Several markers are placed on the user's body. A set of kinematic constraints make the virtual character track these markers. At the same time, we monitor the instantaneous displacements of a set of geometric primitives, called observers, attached to different parts of the virtual character. When an observer enters the influence area of an obstacle, its motion is damped by means of automatically created preventive constraints. The IK solver satisfies both maker and preventive constraints simultaneously, yielding postures of the virtual character that remain close to those of the user, while avoiding collisions with the virtual environment. Our performance measurements show the maturity of the IK technology for real-time full-body interactions.