← ArchivePaper2012

Rig-Space Physics

Fabian Hahn, Sebastian Martin, Bernhard Thomaszewski, Robert W. Sumner, Stelian Coros, Markus Gross

SIGGRAPHDisney Research115 cites2 descendantsRigging CFX

Runs physical simulation directly in the space of an artist rig's parameters, so secondary motion lands on animator-friendly controls.

Open the paper ↗Trace in the lineage graph

Abstract

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 workflow typically employed by artists, as our output consists of animation curves that are identical in nature to the result of manual keyframing. Artists can therefore explore the full spectrum between handcrafted 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. To demonstrate the effectiveness of our method, we create compelling results by adding rich physical motions to coarse input animations. In the absence of artist input, we create realistic passive motion directly in rig space.

How to read this

Category: Method: physics simulation in rig subspace
Contributions: Formulates the equations of motion directly in the subspace of deformations spanned by an animator's rig
Outputs standard animation curves, letting artists blend freely between keyframed and fully simulated motion
Maps rig-parameter stiffness values onto a non-homogeneous FEM material distribution, and uses high-level rig parameters for intuitive editing and speedup
Context: Bridges physics-based FEM simulation and traditional keyframe rigging, projecting dynamics into the animator's control space rather than the full mesh.
Correctness: Demonstrated by adding rich secondary motion to coarse input animations and producing passive motion in the absence of artist input; results live entirely within the rig's expressive range, so motion the rig cannot represent stays out of reach.
Clarity: Accessible in intent; a first pass conveys the rig-space idea, a second pass is needed for the subspace equations of motion and the stiffness-to-material mapping.
How to read it: Focus first on the rig-space formulation and the artist-control story; do a second pass on the subspace EOM and stiffness transform if you intend to implement or evaluate the simulation.

Builds on

Nothing in the archive, this is a starting point.

Built upon by

Complementary Dynamics 2020

Related work

A Unified Approach for Subspace Simulation of Deformable Bodies in Multiple Domains 2015 / TOG
Complementary Dynamics 2020 / SIGGRAPH Asia
FEM Simulation of 3D Deformable Solids: A Practitioner's Guide to Theory, Discretization and Model Reduction 2012 / Course
How the Rig Design Impacts the Animation Process 2021 / DigiPro

Keywords

rig-space physics physically-based simulation finite element method animation rig subspace simulation keyframe animation blend shapes implicit euler integration newton-raphson bfgs schur complement rig-space materials inverse kinematics secondary motion model reduction saint-venant kirchhoff

This page summarises the entry and links to its original source. The archive never hosts or redistributes the publication itself.Show it in the full archive list →