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Metaball Madness: The Rigging of an Implicit Surface Character
Mesh-free character rig for Elio's implicit-surface liquid supercomputer, giving animators full fidelity control over a rigged shader while preserving renderability.
Abstract
We present a novel character rigging solution developed for OOOOO, a liquid supercomputer in Pixar’s Elio. OOOOO’s design and desired movement necessitated reimagining our conventional way of articulating characters and she became Pixar’s first mesh-free character rig. We developed a system that allowed our animators full fidelity control over what is essentially a rigged shader while ensuring downstream renderability. [Luo et al. 2025] The system’s architecture supports a hierarchical arrangement of implicit surface primitives and operators, allowing for complex transformations while preserving normal animation paradigms and offers unprecedented flexibility in character animation.
How to read this
- Category
- Method / production case study: rigging an implicit-surface character
- Contributions
- A mesh-free character rigging solution for OOOOO, a liquid supercomputer in Pixar's Elio, described as Pixar's first mesh-free rig.
- A system giving animators full-fidelity control over what is essentially a rigged shader while preserving downstream renderability.
- An architecture supporting a hierarchical arrangement of implicit-surface primitives and operators, enabling complex transformations within normal animation paradigms.
- Context
- Draws on implicit-surface skin deformation work such as Implicit Skinning (Vaillant et al.), repurposing implicit primitives from skinning into a full animatable rig.Builds on: Implicit Skinning: Real-Time Skin Deformation with Contact Modeling
- Correctness
- Demonstrated on a single bespoke Elio character rather than a general system, so it is production-proven for that case; a reader should keep in mind the approach is tailored to a liquid/implicit-surface design and its reuse on other characters is not the claim.
- Clarity
- Accessible as a case study; a first pass conveys the rigged-shader concept, a second pass clarifies the primitive/operator hierarchy.
- How to read it
- Focus on how implicit primitives and operators map to familiar animation controls while staying renderable; a second pass pays off mainly if you build implicit-surface rigs yourself.
Built upon by
Nothing yet.
Related work
- Eyes Without a Face: Integrating Detached Facial Features into Pixar's Character Pipeline 2023 / SIGGRAPH
- Shaping the Elements: Curvenet Animation Controls in Pixar's Elemental 2023 / SIGGRAPH
- Making Souls: Methods and a Pipeline for Volumetric Characters 2020 / SIGGRAPH
- Mobilizing Mocap, Motion Blending, and Mayhem: Rig Interoperability for Crowd Simulation on Incredibles 2 2018 / SIGGRAPH
Keywords
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