# Data-Driven Physical Face Inversion

## TL;DR

This paper introduces a simple finite element simulation method for facial animation, along with a novel technique to automatically recover actor-specific physical parameters from minimal 3D head pose data, enabling realistic and personalized face simulations.

## Contribution

It presents a new approach to recover physical face parameters using minimal data, improving the realism and ease of tuning in physical face animation methods.

## Key findings

- The method accurately matches real actor face motion.
- Recovered parameters enable realistic, actor-specific face simulations.
- Analysis of spatial material layouts improves simulation quality.

## Abstract

Facial animation is one of the most challenging problems in computer graphics, and it is often solved using linear heuristics like blend-shape rigging. More expressive approaches like physical simulation have emerged, but these methods are very difficult to tune, especially when simulating a real actor's face. We propose to use a simple finite element simulation approach for face animation, and present a novel method for recovering the required simulation parameters in order to best match a real actor's face motion. Our method involves reconstructing a very small number of head poses of the actor in 3D, where the head poses span different configurations of force directions due to gravity. Our algorithm can then automatically recover both the gravity-free rest shape of the face as well as the spatially-varying physical material stiffness such that a forward simulation will match the captured targets as closely as possible. As a result, our system can produce actor-specific, physical parameters that can be immediately used in recent physical simulation methods for faces. Furthermore, as the simulation results depend heavily on the chosen spatial layout of material clusters, we analyze and compare different spatial layouts.