Morphology independent motion retrieval and control

This paper addresses the problem of selecting and adapting a motion in order to make a virtual human interact with a user in real-time. We describe a method that is able to retrieve the most appropriate motion in interactive environments where both the constraints and the character's morphology are not known in advance. The method described here is based on a morphology-independent representation of motion to perform fast motion retargetting and retrieval. Because the size of the database is not infinite, even the best candidate motion may not satisfy precisely all the imposed constraints. As a second step of the algorithm, the selected motion is locally adapted in order to accurately satisfy these constraints. This adaptation allows dealing with a large set of possible movements even if no candidate in the database exactly fits the constraints. In this paper, we propose a method to select an appropriate motion in a small database in order to reduce precomputation, search and manual editing time. To us, an appropriate motion should deal with the morphology of the character and unpredictable constraints imposed in real-time by the user. Indeed, the size of an avatar is not always known in advance in VR applications and the environment induces many adaptations of its original captured motion. In this work, we illustrate our method on a kung-fu fighter that has to kick and punch targets that are interactively displaced. 75 kung-fu motions were performed by 4 actors and will be used by virtual fighters with different sizes and proportions. We so allow the morphology of the virtual fighter to change during the simulation. The method will adapt the animation according to this new character. The target is driven by a real-time motion capture system which tracks the position of the head of the user in an immersive environment. This example demonstrates the ability of our method to deal with average-size databases in an interactive application without requiring long preprocessing.