GaussiAnimate

Official repository of the SIGGRAPH Asia 2026 paper GaussiAnimate: Rig Animatable Categories with Level of Dynamics.

GaussiAnimate turns a temporally registered 3D point sequence into a portable skelebone representation: free-form outer bones for expressive deformation, an inner kinematic skeleton for control, and the motion that connects them.

The core library does not assume a particular reconstruction method. Its input can come from a tracked mesh, Dynamic 3D Gaussians, a monocular Gaussian model, or any other system that gives the same material point a stable index over time.

registered points -> skelebone extraction -> skelebones.npz
                                               |
novel inner pose -------------------------> PartMM -> animated points

There are two ways into this repository. Most users only need the first one.

The Python core supports Python 3.8 through 3.11. Use Python 3.10 on Linux for the full research pipeline; this is the environment used for the source-release installation and native-backend checks.

python -m pip install --upgrade pip setuptools wheel
python -m pip install -e .

This installs the data model, I/O, kinematics, BVH export, PartMM, and the experiment configuration tools. Geometry extraction has two native dependencies and is installed separately below.

Install only the extras you need; the base package does not install PyTorch.

Gaussian training and rendering still use their upstream CUDA environments and rasterizers; these extras do not replace those installations. SMPL/SMPL-X model files and datasets must be obtained separately.

The canonical input is one registered point trajectory, stored as sequence.npz. Every frame must contain the same material points in the same order.

gaussianimate /path/to/sequence.npz --validate-only

For the AMA T_samba example below, validation reports:

{
  "schema_version": 1,
  "frames": 175,
  "points_per_frame": 9971,
  "fps": 30.0,
  "registration_assumed": true,
  "faces": 19938,
  "dtype": "float64"
}

Validation is inexpensive and catches the most common mistakes before SSDR or surface processing begins. The complete array contract is documented under Input Contract.

The repository includes both small native backends: a focused CGAL curve skeleton executable and a lightweight pyssdr binding around the Dem Bones headers. Install their system headers once:

# Ubuntu
sudo apt-get install build-essential cmake libcgal-dev libeigen3-dev python3-dev libx11-6 libgl1 git fonts-dejavu-core libegl1 libegl-mesa0

# macOS
brew install cmake cgal eigen

Then build and verify both backends with one command:

bash scripts/install_geometry.sh

The script installs the Python geometry extra, compiles pyssdr into the selected Python environment, and installs curve_skeleton under .native/bin/. To build only one backend:

bash scripts/install_geometry.sh --pyssdr-only
bash scripts/install_geometry.sh --curve-only

The Python package supports NumPy 1.x (numpy<1.26); the installer rejects NumPy 2 before loading the pinned pybind11 binding. You can override the Python, install prefix, or module directory through the script's documented flags. Run bash scripts/install_geometry.sh --help for the complete list.

The core example uses all 175 registered frames of AMA T_samba, not a generated fixture or a cached skeleton. The meshes come from the official AMA project page; the T_samba meshes archive is about 39.5 MB. After extraction, arrange the files as GA_AMA_ROOT/T_samba/meshes/mesh_*.obj. Point the runner at your local copy:

export GA_AMA_ROOT=/path/to/AMA
python -m skelebone.examples.ama outputs/ama_skelebone

gaussianimate /path/to/sequence.npz outputs/my_asset \
  --mesh /path/to/rest_mesh.ply \
  --visualize

The mesh is optional, but a supplied mesh must be watertight. When no mesh is provided and the registered faces are open, GaussiAnimate uses Poisson only to create a temporary watertight proxy required by CGAL curve skeletonization. SSDR always runs on the original registered point sequence; the Poisson mesh does not replace the input geometry, reconstruction result, skinning target, or exported animated points.

The public hand-off is intentionally small:

outputs/my_asset/
├── skelebones.npz       complete representation consumed by PartMM
├── motion.bvh           portable inner-skeleton motion
├── manifest.json        dimensions, configuration, and artifact paths
├── skelebone.png        optional inspection figure
├── ssdr/                outer-bone decomposition
├── curve_skeleton/      canonical curve and surface correspondence
├── skinning_curve_skeleton/
└── kinematic_tree/      hierarchy and temporal tracking

If the command finishes, downstream code normally needs only skelebones.npz. The remaining directories make each geometric step inspectable and reproducible.

Non-rigid surfaces need two different kinds of structure. A small set of free rigid motions can reproduce cloth, fur, and soft deformation well, but those motions are awkward to edit. A conventional joint hierarchy is easy to control, but cannot express the same surface dynamics by itself.

GaussiAnimate keeps both and binds them explicitly:

The distinction matters in code. J inner joints and B outer bones are not required to have the same count: poses are stored over J, while skinning weights and free-form transforms are stored over B.

save_point_sequence writes the canonical schema:

Registration is the essential assumption: point n must refer to the same material point in every frame. A changing point count or independently sampled frames are not valid inputs.

Orientation and physical units may be chosen freely as long as they stay consistent. Scale still matters, however: extraction includes absolute distance controls such as --joint-merge-distance 0.08. Normalize unusually large or small assets, or tune the distance parameters for their scale.

For Gaussian inputs, points is typically the time series of Gaussian means. Optional per-point colors, opacity, scales, rotations, SH coefficients, and source IDs are retained in point_attributes; extraction operates on means. See the Gaussian and point-cloud guide.

The stable bundle contains no pickled Python objects and can be loaded with NumPy or the public helper:

The bundle also records relative paths to intermediate artifacts so that a result can be inspected without coupling consumers to the pipeline internals.

The high-level API mirrors the command line:

from skelebone import extract_skelebones

result = extract_skelebones(
    "sequence.npz",
    "outputs/my_asset",
    mesh="rest_mesh.ply",  # optional
)

bundle = result.bundle
print(bundle.skeleton.num_joints)
print(bundle.num_bones)
print(result.bundle_path)

The public surface is small on purpose:

• DynamicPointSequence, Skeleton, PoseSequence, and SkeleboneBundle define the representations.
• save_point_sequence, load_point_sequence, save_bundle, and load_bundle provide portable NPZ I/O.
• extract_skelebones is the end-to-end extraction entry point.
• forward_kinematics, fit_pose_to_joint_positions, and export_bvh expose reusable kinematic operations.
• PartMMConfig, PartMotionMatcher, and animate live in partmm.

Lower-level research interfaces for SSDR, surface preparation, curve extraction, joint detection, and tracking are available under skelebone.extraction.

partmm/ is a standalone NumPy package: it can be copied directly into another project without skelebone or the experiment code. See the standalone guide for the direct-array contract and the real VTO T-shirt example.

A novel pose is another portable NPZ:

Create, edit, or import that pose and run:

gaussianimate-animate \
  outputs/my_asset/skelebones.npz \
  novel_pose.npz \
  animation.npz

animation.npz contains:

• points [Q,N,3]
• bone_transforms [Q,B,4,4]
• joint_positions [Q,J,3]
• retrieved source-frame indices for each skeleton part
• scalar fps

Prepare the T-shirt from the official data and SMPL model, then generate a shared-scale temporal preview:

python -m pip install -e '.[visualization]'
python -m partmm.examples.quickstart outputs/partmm_tshirt_demo \
  --bundle resources/partmm/example

The preview shows the SMPL query skeleton, SSDR outer bones, and animated T-shirt.

For the optional pose editor:

python -m pip install -e '.[gui]'
gaussianimate-edit outputs/my_asset/skelebones.npz --output novel_pose.npz

GaussiAnimate/
├── skelebone/                  core representations and extraction pipeline
│   └── extraction/             SSDR, mesh, curve, joint, and tracking stages
├── partmm/                     standalone PartMM, example, visualization, and pose editor
├── experiments/
│   ├── engine/                 config composition, stages, cache, and reports
│   ├── methods/                shared protocol and artifact contracts
│   ├── mesh/                   VTO and DeformingThings4D
│   ├── monocular_gaussian/     monocular Gaussian experiments
│   ├── multiview_gaussian/     D3DGS human experiments
│   └── reproductions/          frozen evidence from related local codebases
├── pyproject.toml              package metadata and command-line entry points
└── THIRD_PARTY_NOTICES.md      upstream code, data, and license boundaries

If you are changing the representation, begin with skelebone/types.py and skelebone/io.py.

python -m pip install build
python -m build

The source archive includes the native backends, scripts, configs, licenses, and README previews. The wheel contains the public Python packages and their declared resources. Datasets, checkpoints, local environments and generated experiment runs are excluded from both Git and release archives.

If GaussiAnimate is useful in your work, please cite:

@article{wang2026gaussianimate,
  title   = {GaussiAnimate: Reconstruct and Rig Animatable Categories with Level of Dynamics},
  author  = {Wang, Jiaxin and Lyu, Dongxin and Cai, Zeyu and Dou, Zhiyang and Lin, Cheng and Chen, Anpei and Xiu, Yuliang},
  journal = {arXiv preprint arXiv:2604.08547},
  year    = {2026}
}

The public Python packages are released under the MIT License. External tools, datasets, pretrained models, and recovered research artifacts retain their own terms. Review THIRD_PARTY_NOTICES.md before redistributing experiment resources.