Flexible Motion In-betweening with Diffusion Models

The official PyTorch implementation of the paper "Flexible Motion In-betweening with Diffusion Models".

For more details, visit our project page.

News

📢 21/June/24 - First release.

Bibtex

If you find this code useful in your research, please cite:

@article{cohan2024flexible,
  title={Flexible Motion In-betweening with Diffusion Models},
  author={Cohan, Setareh and Tevet, Guy and Reda, Daniele and Peng, Xue Bin and van de Panne, Michiel},
  journal={arXiv preprint arXiv:2405.11126},
  year={2024}
}

Getting started

This code was developed on Ubuntu 20.04 LTS with Python 3.7, CUDA 11.7 and PyTorch 1.13.1.

1. Setup environment

Install ffmpeg (if not already installed):

sudo apt update
sudo apt install ffmpeg

For windows use this instead.

2. Install dependencies

This codebase shares a large part of its base dependencies with GMD. We recommend installing our dependencies from scratch to avoid version differences.

Setup virtual env:

python3 -m venv .env_condmdi
source .env_condmdi/bin/activate
pip uninstall ffmpeg
pip install spacy
python -m spacy download en_core_web_sm
pip install git+https://github.com/openai/CLIP.git

Download dependencies:

Text to Motion

bash prepare/download_smpl_files.sh
bash prepare/download_glove.sh
bash prepare/download_t2m_evaluators.sh

Unconstrained

bash prepare/download_smpl_files.sh
bash prepare/download_recognition_unconstrained_models.sh

2. Get data

There are two paths to get the data:

(a) Generation only wtih pretrained text-to-motion model without training or evaluating

(b) Get full data to train and evaluate the model.

a. Generation only (text only)

HumanML3D - Clone HumanML3D, then copy the data dir to our repository:

cd ..
git clone https://github.com/EricGuo5513/HumanML3D.git
unzip ./HumanML3D/HumanML3D/texts.zip -d ./HumanML3D/HumanML3D/
cp -r HumanML3D/HumanML3D diffusion-motion-inbetweening/dataset/HumanML3D
cd diffusion-motion-inbetweening
cp -a dataset/HumanML3D_abs/. dataset/HumanML3D/

b. Full data (text + motion capture)

[Important !] Following GMD, the representation of the root joint has been changed from relative to absolute. Therefore, you need to replace the original files and run GMD's version of motion_representation.ipynb and cal_mean_variance.ipynb provided in ./HumanML3D_abs/ instead to get the absolute-root data.

HumanML3D - Follow the instructions in HumanML3D, then copy the result dataset to our repository:

cp -r ../HumanML3D/HumanML3D ./dataset/HumanML3D

3. Download the pretrained models

Download the model(s) you wish to use, then unzip and place them in ./save/.

Our models are all trained on the HumanML3D dataset.

Conditionally trained on randomly sampled frames and joints (CondMDI)

Conditionally trained on randomly sampled frames

Unconditionally (no keyframes) trained

Motion Synthesis

Text to Motion - Without spatial conditioning

This part is a standard text-to-motion generation.

Generate from test set prompts

using the unconditioned model

python -m sample.synthesize --model_path ./save/condmdi_uncond/model000500000.pt --num_samples 10 --num_repetitions 3

using the conditional model

python -m sample.conditional_synthesis --model_path ./save/condmdi_randomframes/model000750000.pt --edit_mode uncond --num_samples 10 --num_repetitions 3

• You can use --no_text to sample from the conditional model without text conditioning.

Generate from a single prompt

using the unconditioned model

python -m sample.synthesize --model_path ./save/condmdi_uncond/model000500000.pt --num_samples 10 --num_repetitions 1 --text_prompt "a person is exercising and jumping"

using the conditional model

python -m sample.conditional_synthesis --model_path ./save/condmdi_randomframes/model000750000.pt --edit_mode uncond --num_samples 10 --num_repetitions 3 --text_prompt "a person is exercising and jumping"

Text to Motion - With keyframe conditioning

Generate from a single prompt - condition on keyframe locations

using the uncoditioned model

python -m sample.edit --model_path ./save/condmdi_uncond/model000500000.pt --edit_mode benchmark_sparse --transition_length 5 --num_samples 10 --num_repetitions 3 --imputate --stop_imputation_at 1 --reconstruction_guidance --reconstruction_weight 20 --text_condition "a person throws a ball"

• You can remove --text_condition to generate samples conditioned only on keyframes (not text).

using the conditional model

python -m sample.conditional_synthesis --model_path ./save/condmdi_randomframes/model000750000.pt --edit_mode benchmark_sparse --transition_length 5 --num_samples 10 --num_repetitions 3 --text_prompt "a person throws a ball"

Generate from test set prompts - condition on keyframe locations

using the conditional model

python -m sample.conditional_synthesis --model_path ./save/condmdi_randomframes/model000750000.pt --edit_mode benchmark_sparse --transition_length 5 --num_samples 10 --num_repetitions 3

• You can use --no_text to sample from the conditional model without text conditioning.

(In development) Using the --interactive flag will start an interactive window that allows you to choose the keyframes yourself. The interactive pattern will override the predefined pattern.

Useful flags for spatial conditioning:

• --edit_mode to indicate the type of spatial condition.
• --imputation to use imputation/inpainting for inference-time conditioning.
  • stop_imputation_at to indicate the diffusion step to stop replacement. Default is 0.
• --reconstruction_guidance to use reconstruction guidance for inference-time conditioning.
  • --reconstruction_weight to indicate the reconstruction guidance weight ($w_r$ in Algorithm 3)

You may also define:

• --device id.
• --seed to sample different prompts.
• --motion_length (text-to-motion only) in seconds (maximum is 9.8[sec]).
• --progress to save the denosing progress.

Running those will get you:

• results.npy file with text prompts and xyz positions of the generated animation
• sample##_rep##.mp4 - a stick figure animation for each generated motion. You can stop here, or render the SMPL mesh using the following script.

Render SMPL mesh

To create SMPL mesh per frame run:

python -m visualize.render_mesh --input_path /path/to/mp4/stick/figure/file

This script outputs:

• sample##_rep##_smpl_params.npy - SMPL parameters (thetas, root translations, vertices and faces)
• sample##_rep##_obj - Mesh per frame in .obj format.

Notes:

• The .obj can be integrated into Blender/Maya/3DS-MAX and rendered using them.
• This script is running SMPLify and needs GPU as well (can be specified with the --device flag).
• Important - Do not change the original .mp4 path before running the script.

Notes for 3d makers:

• You have two ways to animate the sequence:
  1. Use the SMPL add-on and the theta parameters saved to sample##_rep##_smpl_params.npy (we always use beta=0 and the gender-neutral model).
  2. A more straightforward way is using the mesh data itself. All meshes have the same topology (SMPL), so you just need to keyframe vertex locations. Since the OBJs are not preserving vertices order, we also save this data to the sample##_rep##_smpl_params.npy file for your convenience.

Training

Our model is trained on the HumanML3D dataset.

Conditional Model

python -m train.train_condmdi --keyframe_conditioned

• You can ramove --keyframe_conditioned to train a unconditioned model.
• Use --device to define GPU id.

Evaluate

All evaluation are done on the HumanML3D dataset.

Text to Motion - With keyframe conditioning

• Takes about 20 hours (on a single GPU)
• The output of this script for the pre-trained models (as was reported in the paper) is provided in the checkpoints zip file.
• For each prompt, 5 keyframes are sampled from the ground truth motion. The ground locations of the root joint in those frames are used as conditions.

on the unconditioned model

python -m eval.eval_humanml_condmdi --model_path ./save/condmdi_uncond/model000500000.pt --edit_mode gmd_keyframes --imputate --stop_imputation_at 1

• Above prompt evaluates the inference-time imputation for keyframe conditioning.

on the conditional model

python -m eval.eval_humanml_condmdi --model_path ./save/condmdi_randomframes/model000750000.pt --edit_mode gmd_keyframes --keyframe_guidance_param 1.

Acknowledgments

We would like to thank the following contributors for the great foundation that we build upon: GMD, MDM, guided-diffusion, MotionCLIP, text-to-motion, actor, joints2smpl, MoDi.

License

This code is distributed under an MIT LICENSE.

Note that our code depends on other libraries, including CLIP, SMPL, SMPL-X, PyTorch3D, and uses datasets that each have their own respective licenses that must also be followed.