SNARF: Differentiable Forward Skinning for Animating Non-rigid Neural Implicit Shapes
OPEN ACCESS
Loading...
Author / Producer
Date
2021
Publication Type
Conference Paper
ETH Bibliography
yes
Citations
Altmetric
OPEN ACCESS
Data
Rights / License
Abstract
Neural implicit surface representations have emerged as a promising paradigm to capture 3D shapes in a continuous and resolution-independent manner. However, adapting them to articulated shapes is non-trivial. Existing approaches learn a backward warp field that maps deformed to canonical points. However, this is problematic since the backward warp field is pose dependent and thus requires large amounts of data to learn. To address this, we introduce SNARF, which combines the advantages of linear blend skinning (LBS) for polygonal meshes with those of neural implicit surfaces by learning a forward deformation field without direct supervision. This deformation field is defined in canonical, pose-independent, space, enabling generalization to unseen poses. Learning the deformation field from posed meshes alone is challenging since the correspondences of deformed points are defined implicitly and may not be unique under changes of topology. We propose a forward skinning model that finds all canonical correspondences of any deformed point using iterative root finding. We derive analytical gradients via implicit differentiation, enabling end-to-end training from 3D meshes with bone transformations. Compared to state-of-the-art neural implicit representations, our approach generalizes better to unseen poses while preserving accuracy. We demonstrate our method in challenging scenarios on (clothed) 3D humans in diverse and unseen poses.
Permanent link
Publication status
published
Editor
Book title
2021 IEEE/CVF International Conference on Computer Vision (ICCV)
Journal / series
Volume
Pages / Article No.
11574 - 11584
Publisher
IEEE
Event
18th International Conference on Computer Vision (ICCV 2021)
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
Gestures and body pose
Organisational unit
03979 - Hilliges, Otmar (ehemalig) / Hilliges, Otmar (former)