Conference Paper

Spacetime Vertex Constraints for Dynamically-based Adaptation of Motion-Captured Animation.

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Abstract

We present a novel technique for editing motion captured animation. Our iterative solver produces physicallyplausible adaptated animations that satisfy alterations in foot and hand contact placement with the animated character's surroundings. The technique uses a system of particles to represent the poses and mass distribution of the character at sampled frames of the animation. Constraints between the vertices within each frame enforce the skeletal structure, including joint limits. Novel constraints extending over vertices in several frames enforce the aggregate dynamics of the character, as well as features such as joint acceleration smoothness. We demonstrate adaptation of several animations to altered foot and hand placement.

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... This approach, while possessing the ability to edit different motions, is limited to off-line calculations, as well as the ability to reconstruct only similar motions. Similar to the proposed solution that is presented within this paper, O'Brien et al. [ODC11] proposed a method for handling character's posture based on points, formulating a spacetime optimisation problem that solves altered character motion by using a set of constraints. Boulic et al. [BMT94] proposed a general Inverse Kinetics approach, for controlling the CoM, where the constraint related to the position of the CoM is treated as in any other task; their solutions are solved dif-ferentially, using a special-purpose Jacobian matrix that relates differential changes in the joint coordinates to differential changes in the Cartesian coordinates of the CoM. ...
... [SKG03] where the mass distribution consistent is estimated with reference motions, known to be physically correct. Another similar solution proposed by O'Brien et al. [ODC11] where the CoM of the virtual character is used to represent the poses of the character at sampled frames of the animation. Those, techniques even if can provide desirable results, seems to be limited especially in the case where the generated motion is not resulting from a single motion sequence but from a combination of various integrated motions. ...
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... Although previous approaches about spacetime optimization show a wide variety of high quality movements can be synthesized by spacetime constraints, the high computational costs make it difficult to be applied to interactive or realtime applications. O'Brien et al. [O'Brien et al. 2011] represents the body by a series of vertices instead of segments to accelerate the optimization process. We also use such a representation to improve the performance. ...
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advantage and that copies show this notice on the fi rst page or initial screen of a display along with the full citation. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, to redistribute to lists, or to use any component of this work in other works requires prior specifi c permission and/or a fee. Permissions may be requested from Publications Dept. Abstract Character animation in video games—whether manually key-framed or motion captured—has traditionally relied on codifying skeletons early in a game's development, and creating animations rigidly tied to these fixed skeleton morphologies. This paper in-troduces a novel system for animating characters whose morpholo-gies are unknown at the time the animation is created. Our au-thoring tool allows animators to describe motion using familiar posing and key-framing methods. The system records the data in a morphology-independent form, preserving both the animation's structural relationships and its stylistic information. At runtime, the generalized data are applied to specific characters to yield pose goals that are supplied to a robust and efficient inverse kinematics solver. This system allows us to animate characters with highly varying skeleton morphologies that did not exist when the anima-tion was authored, and, indeed, may be radically different than any-thing the original animator envisioned.
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