ProtoMotions: Physics-based Character Animation

“Primitive or fundamental types of movement that serve as a basis for more complex motions.”

• What is this?
• Installation guide
• Training built-in agents
• Evaluating your agent
• Building your own agent/environment

What is this?

This codebase contains our efforts in building interactive physically-simulated virtual agents. It supports both IsaacGym and IsaacSim.

Changelog

v1.0

Public release!

Important:
This codebase builds heavily on Hydra and OmegaConfig.
It is recommended to familiarize yourself with these libraries and how config composition works.

Installation

This codebase supports both IsaacGym and IsaacSim. You can install one or both and the simulation backend is selected via the configuration file.

First run git lfs fetch --all to fetch all files stored in git-lfs.

IsaacGym

1. Install IsaacGym, install using python 3.8.
2. Once IG and PyTorch are installed, from the repository root install the Phys-Anim package and its dependencies with:

pip install -e .
pip install -e isaac_utils
pip install -e poselib

Set the PYTHON_PATH env variable (not really needed, but helps the instructions stay consistent between sim and gym).

alias PYTHON_PATH=python

Potential Issues

If you have python errors:

export LD_LIBRARY_PATH=${CONDA_PREFIX}/lib/

If you run into memory issues -- try reducing the number of environments by adding to the commandline num_envs=1024

IsaacSim

Important:
IsaacSim integration on-going. Some features may not work yet.

1. Install IsaacSim
2. Set PYTHON_PATH

For Linux: alias PYTHON_PATH=~/.local/share/ov/pkg/isaac-sim-*/python.sh
For Windows: doskey PYTHON_PATH=C:\Users\user\AppData\Local\ov\pkg\isaac_sim-*\python.bat $*
For IsaacSim Docker: alias PYTHON_PATH=/isaac-sim/python.sh

3. Once IsaacSim is installed - from the repository root install the Physical Animation package and its dependencies with:

PYTHON_PATH -m pip install -e .
PYTHON_PATH -m pip install -e isaac_utils
PYTHON_PATH -m pip install -e poselib

Training Your Agent

Backbone and Robot selection

If you are using IsaacGym use the flag +backbone=isaacgym. For IsaacSim use +backbone=isaacsim. Then select the robot you are training. For example, the SMPL humanoid robot is +robot=smpl. The code currently supports:

Robot	Description
smpl	SMPL humanoid
smplx	SMPL-X humanoid
amp	Adversarial Motion Priors humanoid
sword_and_shield	ASE sword and shield character
h1	Unitree H1 humanoid with end-effector and head joints made visible

Provided Algorithms

MaskedMimic

In the first stage, you need to train a general motion tracker. At each step, this model receives the next K future poses. The second phase trains the masked mimic model to reconstruct the actions of the expert tracker trained in the first stage.

1. Train full body tracker: Run PYTHON_PATH phys_anim/train_agent.py +exp=full_body_tracker +robot=smpl +backbone=isaacgym motion_file=<motion file path>
2. Find the checkpoint of the first phase. The next training should point to that folder and not the checkpoint.
3. Train MaskedMimic: Run PYTHON_PATH phys_anim/train_agent.py +exp=masked_mimic +robot=smpl +backbone=isaacgym motion_file=<motion file path> gt_actor_path=<path to phase 1 folder>
4. Inference: For an example of user-control, run PYTHON_PATH phys_anim/eval_agent.py +robot=smpl +backbone=isaacgym +opt=[masked_mimic/tasks/user_control] motion_file=<motion file path> checkpoint=<path to maskedmimic checkpoint>

add force_flat_terrain=True to use a default flat terrain (this reduces loading time).

Full body motion tracking

This model is the first stage in training MaskedMimic. Refer to the MaskedMimic section for instructions on training this model.

AMP

Adversarial Motion Priors (AMP, arXiv) trains an agent to produce motions with similar distributional characteristics to a given motion dataset. AMP can be combined with a task, encouraging the agent to solve the task with the provided motions.

1. Run PYTHON_PATH phys_anim/train_agent.py +exp=amp motion_file=<path to motion file>.
2. Choose your robot, for example +robot=amp.
3. Set +backbone=isaacgym or +backbone=isaacsim to choose the backbone.

Path Following

One such task for AMP is path following. The character needs to follow a set of markers. To provide AMP with a path following task, similar to PACER, run the experiment +exp=path_follower.

ASE

Adversarial Skill Embeddings (ASE, arXiv) trains a low-level skill generating policy. The low-level policy is conditioned on a latent variable z. Each latent variable represents a different motion. ASE requires a diverse dataset of motions, as opposed to AMP that can (and often should) be trained on a single (or small set of motions) motion.

Run PYTHON_PATH phys_anim/train_agent.py +exp=ase motion_file=<path to motion dataset>

In order to train the sword-and-shield character, as in the original paper:

1. Git clone ASE
2. Download the data from ASE
3. Point the motion_file path to the dataset descriptor file dataset_reallusion_sword_shield.yaml (from the ASE codebase)
4. Use the robot +robot=sword_and_shield

Terrain

ProtoMotions handles the terrain generation in all experiments. By default we create a flat terrain that is large enough for all humanoids to spawn with comfortable spacing between them. This is similar to the classic env_spacing in IsaacGym. By add the flag +terrain=complex, the simulation will add an irregular terrain and normalize observations with respect to the terrain beneath the character. By default this terrain is a combination of stairs, slopes, gravel and also a flat region. To make the controller aware of the terrain we add the terrain observations using the flag +terrain=terrain_obs. It is recommended to use an experiment file and add these flags in there. See phys_anim/config/exp/masked_mimic.yaml for an example.

During inference you can force a flat, and simple, terrain (similar to the default IsaacGym ground plane), by force_flat_terrain=True or by overriding the terrain type using +terrain=flat. This is useful for inference, if you want to evaluate a controller (where the saved config defines a complex terrain) on a flat and simple terrain.

Scenes

Similar to the motion library, we introduce SceneLib. This scene-management library handles spawning scenes across the simulated world. Scenes can be very simple, but can also be arbitrarily complex. The simplest scenes are a single non-movable object, for example from the SAMP dataset. Complex scenes can have one-or-more objects and these objects can be both non-movable and also moveable. Each object has a set of properties, such as the position within the scene, and also a motion file that defines the motion of the object when performing motion-tracking tasks.

For more information, refer to the example YAML files in the data/yaml_files folder.

Logging

By default, all experiments are logged using tensorboard. You can also log using Weights and Biases by adding the flag +opt=wdb.

Evaluation/Visualization

To evaluate the trained agent

1. Find the checkpoint. results/<experiment name>/lightning_logs/version_<number>
2. Evaluate using PYTHON_PATH phys_anim/eval_agent.py +robot=<robot> +backbone=<backend> motion_file=<path to motion file> checkpoint=results/<experiment name>/lightning_logs/version_<number>/last.ckpt.
3. By setting headless=False it will also render (live visualization) the evaluation.

We provide a set of pre-defined keyboard controls.

Key	Description
J	Apply physical force to all robots (tests robustness)
L	Toggle recording video from viewer. Second click will save frames to video
;	Cancel recording
U	Update inference parameters (e.g., in MaskedMimic user control task)

Code structure, how can I build my own stuff?

The code is split into the standard env-agent RL dichotomy.

Agents

The agent code (located in phys_anim/agents) controls the logic of the agent. For example, ASE, implemented within the InfoMax class, inherits the following tree: PPO -> AMP -> InfoMax.

Environments

The agent training code is agnostic to the backbone simulative environment. This is not true for the environment.

The environment code is located in phys_anim/envs. The first folder defines the environment type, for example amp. Within each environment folder we have common.py which contains all the core logic for the environment, and isaacgym.py, isaacsim.py, etc... which contain the simulator specific code (e.g., IsaacGym API calls).

Configurations

This repo is aimed to be versatile and fast to work with. Everything should be configurable, and elements should be composable by combining configs. For example, the opt folder contains a collection of config options. Some of them are:

• wdb: Log using Weights and Biases.
• disable_discriminator: Disabling AMP discriminator for classes inheriting from AMP.
• legged-robot: Configurations for legged robots (e.g., Unitree H1).
• record_motion: Record motions (states) to a file.
• record_video: Record videos to a file.

Data

Training the agents requires using mocap data. The motion_file parameter receives either an .npy file, for a single motion, or a .yaml for an entire dataset of motions. Keep in mind that scene-based information is only extracted from the .yaml files, making them a requirement for such tasks.

We provide 4 example motions to get you started:

• AMP humanoid: phys_anim/data/motions/amp_humanoid_walk.npy
• AMP + sword and shield humanoid: phys_anim/data/motions/amp_sword_and_shield_humanoid_walk.npy
• SMPL humanoid: phys_anim/data/motions/smpl_humanoid_walk.npy
• SMPL-X humanoid: phys_anim/data/motions/smplx_humanoid_walk.npy
• H1 (with head and hands): phys_anim/data/motions/h1_punch.npy

The data processing pipeline follows the following procedure:

1. Download the data.
2. Convert AMASS to Isaac (PoseLib) format.
3. Create a YAML file with the data information (filename, FPS, textual labels, etc...).
4. Package (pre-process) the data for faster loading.

Motions can be visualized via kinematic replay by running PYTHON_PATH phys_anim/scripts/play_motion.py <motion file> <backbone isaacgym/isaacsim> <robot type>.

Download Data

1. Download the SMPL v1.1.0 parameters and place them in the data/smpl/ folder. Rename the files basicmodel_neutral_lbs_10_207_0_v1.1.0, basicmodel_m_lbs_10_207_0_v1.1.0.pkl, basicmodel_f_lbs_10_207_0_v1.1.0.pkl to SMPL_NEUTRAL.pkl, SMPL_MALE.pkl and SMPL_FEMALE.pkl.
2. Download the SMPL-X v1.1 parameters and place them in the data/smpl/ folder. Rename the files to SMPLX_NEUTRAL.pkl, SMPLX_MALE.pkl and SMPLX_FEMALE.pkl.
3. Download the AMASS dataset.
4. Download the SAMP dataset.

Convert the motions to MotionLib format

1. Run python data/scripts/convert_amass_to_isaac.py <path_to_AMASS_data> set --humanoid-type=smplx if using SMPL-X.
2. Run python data/scripts/convert_samp_to_isaac.py <path_to_SAMP_data> set --humanoid-type=smplx if using SMPL-X.
3. Copy the converted SAMP data to the AMASS data directory. SAMP-filtered.yaml requires it in the samp-smpl/ sub-folder and SAMP-X-filtered.yaml in the samp-smplx/ sub-folder.

YAML files

You can create your own YAML files for full-control over the process.

Create your own YAML files

Example pre-generated YAML files are provided in `data/yaml_files`. To create your own YAML file, follow these steps:

1. Download the textual labels, index.csv, train_val.txt, and test.txt` from the HML3D dataset.
2. Run python data/scripts/create_motion_fps_yaml.py and provide it with the path to the extracted AMASS (or AMASS-X) data. This will create a .yaml file with the true FPS for each motion. If using AMASS-X, provide it with the flags --humanoid-type=smlx and --amass-fps-file that points to the FPS file for the original AMASS dataset (e.g. data/yaml_files/motion_fps_smpl.yaml).
3. Run python data/scripts/process_hml3d_data.py <yaml_file_path> --relative-path=<path_to_AMASS_data> set --occlusion-data-path=data/amass/amassx_occlusion_v1.pkl, --humanoid-type=smplx and --motion-fps-path=data/yaml_files/motion_fps_smplx.yaml if using SMPL-X.
4. To also include flipped motions, run python data/scripts/create_flipped_file.py <path_to_yaml_file_from_last_step>. Keep in mind that SMPL-X seems to have certain issues with flipped motions. They are not perfectly mirrored.
5. To include the SAMP data, run python data/scripts/merge_amass_with_samp.py <path_to_amass_yaml_file_from_last_step> <path_to_samp_yaml_file> <path_to_combined_output_file>. An example SAMP file can be found in data/yaml_files/SAMP-filtered.yaml or SAMP-X-filtered.yaml for SMPL-X.

Alternatively, you can use the pre-generated YAML files in data/yaml_files.

Package the data for faster loading

Run python data/scripts/package_motion_lib.py <path_to_yaml_file> <path_to_AMASS_data_dir> <output_pt_file_path> set --humanoid-type=smplx if using SMPL-X. Add the flag --create-text-embeddings to create text embeddings (for MaskedMimic).

Citation

This codebase builds upon prior work from NVIDIA and external collaborators. Please adhere to the relevant licensing in the respective repositories. If you use this code in your work, please consider citing our works:

@inproceedings{tessler2024masked,
  title={MaskedMimic: Unified Physics-Based Character Control Through Masked Motion},
  author={Tessler, Chen and Guo, Yunrong and Nabati, Ofir and Chechik, Gal and Peng, Xue Bin},
  booktitle={ACM Transactions On Graphics (TOG)},
  year={2024},
  publisher={ACM New York, NY, USA}
}

@inproceedings{tessler2023calm,
  title={CALM: Conditional adversarial latent models for directable virtual characters},
  author={Tessler, Chen and Kasten, Yoni and Guo, Yunrong and Mannor, Shie and Chechik, Gal and Peng, Xue Bin},
  booktitle={ACM SIGGRAPH 2023 Conference Proceedings},
  pages={1--9},
  year={2023},
}

Also consider citing these prior works that helped contribute to this project:

@inproceedings{juravsky2024superpadl,
  title={SuperPADL: Scaling Language-Directed Physics-Based Control with Progressive Supervised Distillation},
  author={Juravsky, Jordan and Guo, Yunrong and Fidler, Sanja and Peng, Xue Bin},
  booktitle={ACM SIGGRAPH 2024 Conference Papers},
  pages={1--11},
  year={2024}
}

@inproceedings{luo2024universal,
    title={Universal Humanoid Motion Representations for Physics-Based Control},
    author={Zhengyi Luo and Jinkun Cao and Josh Merel and Alexander Winkler and Jing Huang and Kris M. Kitani and Weipeng Xu},
    booktitle={The Twelfth International Conference on Learning Representations},
    year={2024},
    url={https://openreview.net/forum?id=OrOd8PxOO2}
}

@inproceedings{Luo2023PerpetualHC,
    author={Zhengyi Luo and Jinkun Cao and Alexander W. Winkler and Kris Kitani and Weipeng Xu},
    title={Perpetual Humanoid Control for Real-time Simulated Avatars},
    booktitle={International Conference on Computer Vision (ICCV)},
    year={2023}
}            

@inproceedings{rempeluo2023tracepace,
    author={Rempe, Davis and Luo, Zhengyi and Peng, Xue Bin and Yuan, Ye and Kitani, Kris and Kreis, Karsten and Fidler, Sanja and Litany, Or},
    title={Trace and Pace: Controllable Pedestrian Animation via Guided Trajectory Diffusion},
    booktitle={Conference on Computer Vision and Pattern Recognition (CVPR)},
    year={2023}
} 

@inproceedings{hassan2023synthesizing,
  title={Synthesizing physical character-scene interactions},
  author={Hassan, Mohamed and Guo, Yunrong and Wang, Tingwu and Black, Michael and Fidler, Sanja and Peng, Xue Bin},
  booktitle={ACM SIGGRAPH 2023 Conference Proceedings},
  pages={1--9},
  year={2023}
}

References and Thanks

This project repository builds upon the shoulders of giants.

• IsaacGymEnvs for reference IsaacGym code. For example, terrain generation code.
• OmniIsaacGymEnvs for reference IsaacSim code.
• DeepMimic our full body tracker (Mimic) can be seen as a direct extension of DeepMimic.
• ASE/AMP for adversarial motion generation reference code.
• PACER for path generator code.
• PADL/SuperPADL for initial code structure with PyTorch lightning
• PHC for AMASS preprocessing and conversion to Isaac (PoseLib) and reference on working with SMPL robotic humanoid.
• SMPLSim for SMPL and SMPL-X simulated humanoid.
• OmniH2O and PHC-H1 for AMASS to Isaac H1 conversion script.
• rl_games for reference PPO code.

Also special thanks to

• Kelly Guo for the constant help with IsaacGym/Sim!
• Evgeny Tumanov for ASE IsaacSim reference code.

Dependencies

This project uses the following packages:

• PyTorch, LICENSE
• PyTorch Lightning, LICENSE
• IsaacGym, LICENSE
• IsaacSim, LICENSE
• SMPLSim, LICENSE