Add SMPL-X (GRAB) and MJCF humanoid importers#20
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GRABImporter: loads a GRAB sequence (SMPL-X body + grasped object + table) into the ModelImporter contract via SMPL-X forward kinematics, with per-finger surface-to-surface contact detection (downsampled hand verts vs object mesh). MJCFImporter: generic MuJoCo MJCF importer (nested body tree; capsule/box/sphere geoms tessellated), used to load the InterMimic SMPL-X humanoid (omomo.xml). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Overview
This PR adds two model importers that bring SMPL-X grasping data and an articulated SMPL-X humanoid into AI4Animation, so captured hand–object interaction can be loaded, visualized, and retargeted within the framework.
The motivating use case: load a GRAB sequence (a subject grasping an object) and reproduce the same grasp on the InterMimic/InterPrior SMPL-X humanoid (
omomo.xml), preserving the per-finger spatial–temporal contact.Demo
Captured SMPL-X (GRAB) grasp (left) vs. the same motion retargeted onto the omomo SMPL-X humanoid (right), camera following the body:
Full-resolution clip:
docs/media/grasp_compare_smplx_omomo.mp4What's added
GRABImporter(ai4animation/Import/GRABImporter.py) — loads a GRAB sequence (SMPL-X body + grasped object + table) into the framework via SMPL-X forward kinematics: the subject body mesh is skinned to the 55 SMPL-X joints, and the object/table are appended as rigid meshes on their captured trajectories. Includes per-finger surface-to-surface contact detection (downsampled hand mesh vertices vs. the object mesh, via a KD-tree) with a soft contact-weight ramp.MJCFImporter(ai4animation/Import/MJCFImporter.py) — a generic MuJoCo MJCF importer that parses the nested<body>tree and tessellates capsule/box/sphere geoms into meshes; used to load the articulated SMPL-X humanoid.Both conform to the existing
ModelImportercontract (JointNames/JointParents/JointMatrices/Meshes/Skin) and were verified to import and instantiate against a clean checkout ofmain.Dependencies
Runtime:
smplx,trimesh,scipy.Co-authored-by: Claude Opus 4.8 noreply@anthropic.com