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Phace: Physics-based Face Modeling and Animation
Alexandru Eugen Ichim, Petr Kadlecek, Ladislav Kavan, Mark Pauly
Simulates facial expressions via nonlinear energies modeling passive flesh, active muscles, and rigid bone; supports inertia, skin sliding, and collision handling.
Abstract
We present a novel physics-based approach to facial animation. Contrary to commonly used generative methods, our solution computes facial expressions by minimizing a set of non-linear potential energies that model the physical interaction of passive flesh, active muscles, and rigid bone structures. By integrating collision and contact handling into the simulation, our algorithm avoids inconsistent poses commonly observed in generative methods such as blendshape rigs. A novel muscle activation model leads to a robust optimization that faithfully reproduces complex facial articulations. We show how person-specific simulation models can be built from a few expression scans with a minimal data acquisition process and an almost entirely automated processing pipeline. Our method supports temporal dynamics due to inertia or external forces, incorporates skin sliding to avoid unnatural stretching, and offers full control of the simulation parameters, which enables a variety of advanced animation effects. For example, slimming or fattening the face is achieved by simply scaling the volume of the soft tissue elements. We show a series of application demos, including artistic editing of the animation model, simulation of corrective facial surgery, or dynamic interaction with external forces and objects.
How to read this
- Category
- Method: physics-based face modeling and animation
- Contributions
- Phace, a physics-based facial animation method that computes expressions by minimizing nonlinear potential energies over passive flesh, active muscles, and rigid bone
- A novel muscle activation model plus integrated collision and contact handling that avoids the inconsistent poses common to generative blendshape rigs
- Person-specific simulation models built from a few expression scans via a near-automatic pipeline, with temporal dynamics, skin sliding, and editing effects such as scaling soft-tissue volume
- Context
- Builds on personalized anatomical body modeling (Kadlecek et al., Reconstructing Personalized Anatomical Models for Physics-based Body Animation), bringing a physics-simulation alternative to generative blendshape facial animation.Builds on: Reconstructing Personalized Anatomical Models for Physics-based Body Animation
- Correctness
- Person-specific models are built from only a few expression scans; readers should note the realism depends on the simulation parameters and the quality of those scans, and physics-based solving is generally heavier and harder to direct than blendshape evaluation.
- Clarity
- Conceptually clear but technically dense; a first pass conveys the simulate-instead-of-blend idea, a second and likely third pass are needed for the energy formulation and activation model.
- How to read it
- Read first for why physical simulation avoids blendshape artifacts; do a careful second pass on the energy terms and muscle activation model if you plan to build or evaluate a physics-based face rig.
Related work
- An Implicit Physical Face Model Driven by Expression and Style 2023 / SIGGRAPH Asia
- SoftDECA: Computationally Efficient Physics-Based Facial Animations 2023 / MIG
- BlendForces: A Dynamic Framework for Facial Animation 2016 / CGF
- Lessons from the Evolution of an Anatomical Facial Muscle Model 2017 / DigiPro
Keywords
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