Rig-Space Physics

Project Members

Fabian Hahn (Disney Research Zurich)
Sebastian Martin (Disney Research Zurich)
Bernhard Thomaszewski (Disney Research Zurich)
Bob Sumner (Disney Research Zurich)
Stelian Coros (Disney Research Zurich)
Markus Gross (Disney Research Zurich)



A result of our method: given a character rig and a set of keyframes for some of its parameters, our method automatically produces animation curves for the remaining parameters by solving the equations of motion in the space of deformations defined by the rig. The resulting motion is physically plausible, maintains the original artistic intent, and is easily editable.

In animated films, believable and compelling character animation, requires careful consideration of the complex physical forces involved in movement in order to give weight and substance to an otherwise empty and weightless shape. In current animation pipelines, the disconnect between the workflow used by artists (manually keyframing a small set of rig parameters) and the output of physics-based simulations (a high number of independent degree of freedom) limits the effectiveness of physical simulation in the animation pipeline. To date, artists must choose between laboriously keyframing physical effects or employing physics-based tools that offer limited control and may not respect the character’s range of meaningful deformations.

We present a method that brings the benefits of physics-based simulations to traditional animation pipelines. We formulate the equations of motions in the subspace of deformations defined by an animator’s rig. Our framework fits seamlessly into the work-flow typically employed by artists, as our output consists of animation curves that are identical in nature to the result of manual key framing. Artists are therefore capable of exploring the full spectrum between hand-crafted animation and unrestricted physical simulation. To enhance the artist’s control, we provide a method that transforms stiffness values defined on rig parameters to a non-homogeneous distribution of material parameters for the underlying FEM model. In addition, we use automatically extracted high-level rig parameters to intuitively edit the results of our simulations, and also to speed up computation. Our method treats all rigging controls in a unified manner and thus works with skeletons, blend shapes, spatial deformation fields, or any other rigging procedure. Moreover, the output of our system consists of animation keyframes for the rig parameters, making editing convenient for the artist. To demonstrate the effectiveness of our method, we create compelling results by adding rich, secondary motions to coarse input animations.


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Rig-Space Physics
August 5, 2012
Paper File [pdf, 10.46 MB]

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