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Patch-based Surface Relaxation
Fernando de Goes, William Sheffler, Michael Comet, Alonso Martinez, Aimei Kutt
Transfers a desired edge-loop patch layout from a reference mesh to deformed meshes via decal-map-weighted relaxation, used on Bao and Incredibles 2.
Abstract
From rigging to post-simulation cleanups, surface relaxation is a widely used procedure in feature animation. Over the years, Pixar has experimented with several techniques for this task, mostly based on variants of Laplacian smoothing. Notably, none of existing approaches are suited to reproduce the patch layout of a baseline mesh. This is of particular interest for modeling the span of edge flows, or for restoring the rest configuration of a mesh under large deformations. To achieve this goal, we developed a new patch-aware relaxation method for general polygonal meshes. Our approach encompasses three main contributions. We first introduce a weighting scheme that uses local decal maps to encode the structure of edge flows formed by the desirable patch layout. We then propose an update rule that transfers a reference patch arrangement to a deformed mesh. To control volume preservation, we also present a surface-constrained regime that exploits decal maps to slide points within the surface. We demonstrate the effectiveness and versatility of our tool with a series of examples from Pixar's short Bao and feature film Incredibles 2.
How to read this
- Category
- Method: a patch-aware mesh surface relaxation technique
- Contributions
- A weighting scheme using local decal maps to encode the desired patch layout and edge flows
- An update rule that transfers a reference patch arrangement onto a deformed mesh
- A surface-constrained regime exploiting decal maps to slide points for volume preservation
- Context
- Extends classic Laplacian-style smoothing used in feature animation, adding patch-layout awareness that prior relaxation variants did not reproduce.
- Correctness
- Demonstrated on examples from Pixar's Bao and Incredibles 2; as a production-motivated tool, its effectiveness depends on having a meaningful reference patch layout and well-authored decal maps, which a reader should keep in mind.
- Clarity
- Reasonably accessible if you know Laplacian smoothing; a first pass conveys the patch-transfer goal, a second pass clarifies the weighting and update rules.
- How to read it
- First pass for the motivation (reproducing edge-loop layout under deformation) and the three contributions; do a second pass on the decal-map weighting and update rule if you need to reimplement the relaxation.
Builds on
Nothing in the archive, this is a starting point.
Related work
- Implicit Skinning: Real-Time Skin Deformation with Contact Modeling 2013 / SIGGRAPH
- Delta Mush: Smoothing Deformations While Preserving Detail 2014 / DigiPro
- Character Rigging, Deformations, and Simulations in Film and Game Production 2011 / SIGGRAPH Courses
- Harmonic Coordinates for Character Articulation 2007 / SIGGRAPH
Keywords
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