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An Empirical Rig for Jaw Animation
Empirically derived rig for realistic jaw animation, capturing biomechanical jaw motion from data for use in facial character rigs.
Abstract
In computer graphics the motion of the jaw is commonly modelled by up-down and left-right rotation around a fixed pivot plus a forward-backward translation, yielding a three dimensional rig that is highly suited for intuitive artistic control. The anatomical motion of the jaw is, however, much more complex since the joints that connect the jaw to the skull exhibit both rotational and translational components. In reality the jaw does not move in a three dimensional subspace but on a constrained manifold in six dimensions. We analyze this manifold in the context of computer animation and show how the manifold can be parameterized with three degrees of freedom, providing a novel jaw rig that preserves the intuitive control while providing more accurate jaw positioning. The chosen parameterization furthermore places anatomically correct limits on the motion, preventing the rig from entering physiologically infeasible poses. Our new jaw rig is empirically designed from accurate capture data, and we provide a simple method to retarget the rig to new characters, both human and fantasy.
How to read this
- Category
- Method: an empirically derived jaw rig for facial animation
- Contributions
- Analyzes the jaw's motion as a constrained six-dimensional manifold rather than the usual three-DOF fixed-pivot model
- Parameterizes that manifold with three degrees of freedom, keeping intuitive artistic control while improving positional accuracy
- Places anatomically correct limits to prevent infeasible poses, with a simple method to retarget the rig to new human and fantasy characters
- Context
- Builds on production facial performance capture (e.g. Medusa: A Production-Ready Photoreal Facial Performance Capture System) by using captured data to design a more anatomically faithful jaw rig.Builds on: High-Quality Passive Facial Performance Capture Using Anchor Frames
- Correctness
- Empirically designed from accurate capture data and constrained to physiologically feasible motion; accuracy is therefore tied to the captured subjects, and the retargeting to fantasy characters extrapolates beyond the human anatomy the manifold was derived from, which a reader should keep in mind.
- Clarity
- Clear and well-motivated; a first pass conveys the manifold insight, a second pass clarifies the parameterization.
- How to read it
- First pass for the 6D-manifold insight and the three-DOF parameterization; second pass on the manifold fitting and retargeting if building or improving a facial jaw rig.
Related work
- Direct Manipulation Blendshapes 2010 / TOG
- Sketch-Based Controllers for Blendshape Facial Animation 2015 / Eurographics
- Direct manipulation of blendshapes using a sketch-based interface 2018 / Web3D
- Transposition Based Blendshape Direct Manipulation 2017 / GRAPP
Keywords
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