Geometry Processing with Neural Fields

Pytorch implementation for the NeurIPS 2021 paper (project page):

Geometry Processing with Neural Fields

Guandao Yang, Serge Belongie, Bharath Hariharan, Vladlen Koltun

Introduction

Most existing geometry processing algorithms use meshes as the default shape representation.
Manipulating meshes, however, requires one to maintain high quality in the surface discretization.
For example, changing the topology of a mesh usually requires additional procedures such as remeshing. This paper instead proposes the use of neural fields for geometry processing. Neural fields can compactly store complicated shapes without spatial discretization. Moreover, neural fields are infinitely differentiable, which allows them to be optimized for objectives that involve higher-order derivatives. This raises the question: can geometry processing be done entirely using neural fields? We introduce loss functions and architectures to show that some of the most challenging geometry processing tasks, such as deformation and filtering, can be done with neural fields. Experimental results show that our methods are on par with the well-established mesh-based methods without committing to a particular surface discretization.

Installation

This repository provides a Anaconda environment, and requires NVIDIA GPU to run the optimization routine. The code is tested in CUDA 10.2, ubuntu 16.04. The environment can be set-up using the following commands:

conda env create -f environment.yml
conda activate NFGP

Dataset

We offer pre-processed dataset for reproducing the experimental results in the paper. The instruciton is in section Download Dataset. If you want to run experiment for your own shape, you need to prepare data in the following two steps:

1. Create SDF samples for the shape (See section Create SDF Samples)
2. Train a neural field to fit those samples (See section Create Input Neural Fields).
3. Depending on the tasks, create the user specified input. For deofmration task, please refer to section Create Deformation Handles. For sharpening and smoothing, you can directly set it through the configuration file or the hyper-parameter.

Download Dataset

You can find the dataset in the following Google drive folder: Google Drive. Alternatively, you can also download data using the following command:

# Download data to train Neural Fields
wget https://geometry-processing-with-neural-fields.s3.us-east-2.amazonaws.com/nf_data.zip
unzip nf_data.zip

# Download the deformation Data
wget https://geometry-processing-with-neural-fields.s3.us-east-2.amazonaws.com/deform_data.zipA
unzip deform_data.zip

We also provide pretrained neural fields for convenience:

wget https://geometry-processing-with-neural-fields.s3.us-east-2.amazonaws.com/nf_pretrained.zip
unzip nf_pretrained.zip

Create SDF Samples

Following command creates SDF ground truth samples for obtaining the Neural Fields that approximates the SDF of the shape.

python scripts/prep_sdf_data.py <mesh_file_name> --out_path data/<mesh_file_name>

# Example
python scripts/prep_sdf_data.py armidillo.obj --out_path data/armidillo

The data preprocessing pipeline will sample 5M points uniformly withint [-1, 1]^3 and another 5M near surface (i.e . surface plus a Gaussian with standard deviation of 0.1). We then use the mesh_to_sdf package to compute the SDF of the points. These points will be saved to following files:

• <out_path>/mesh.obj : a copy of the original mesh.
• <out_path>/sdf.npy : a numpy file that contains the sampled points, their SDF, and the original mesh.

Note that this pipeline works the best with watertight mesh. This processing pipeline takes about 5 - 10 minutes to finish for a mesh with 30k faces.

Create Input Neural Fields

Once you've obtained the sdf.npy file in the previous subsection, you can use those data to train a neural field:

python train.py configs/recon/create_neural_fields.yaml --hparams data.path=<your_sdf.npy>

You can also create your own config following the examples in folder configs/recon.

Create Deformation Handles

Please see notebooks/deformation-handles-*.ipynb for examples.

Smoothing and Sharpening

To run our methods on the smoothing or sharpening task, you can use the following configurations:

# Armadillo
python train.py configs/filtering/filtering_Armadillo_beta0.yaml  # smoothing
python train.py configs/filtering/filtering_Armadillo_beta2.yaml  # sharpening
# Noisy sphere
python train.py configs/filtering/filtering_HalfNoisySphere_beta0.yaml # smoothing
python train.py configs/filtering/filtering_HalfNoisySphere_beta2.yaml # sharpening
# Noisy torus
python train.py configs/filtering/filtering_NoisyTorus_beta0.yaml # smoothing
python train.py configs/filtering/filtering_NoisyTorus_beta2.yaml # sharpening

You can change the value of beta by adding --hparams trainer.beta=<yourbeta>. To run it on a different shape, you need to change the models.decoder to load the appropriate neural fields.

Deformation

To run the deformation experiments, you can use the following configurations:

# Jolteon
python train.py configs/deformation/jolteon_jump_s1e-1_b1e-3.yaml
python train.py configs/deformation/jolteon_nosedown_s1e-1_b1e-3.yaml

To change the amount of bending or stretching resistent, you can change the value of trainer.loss_stretch.weight and trainer.loss_bend,weught by adding --hparams trainer.loss_stretch.weight=<new_weight> or --hparams trainer.loss_bend.weight=<new_weight>

To visualize the results, you can use the notebook notebooks/visualize-deformation.ipynb.

Citation

If you find our paper or code useful, please cite us:

@inproceedings{yang2021geometry,
  title={Geometry Processing with Neural Fields},
  author={Yang, Guandao and Belongie, Serge and Hariharan, Bharath and Koltun, Vladlen},
  booktitle={Thirty-Fifth Conference on Neural Information Processing Systems},
  year={2021}
}

Acknowledgement

Guandao’s PhD was supported in part by a research gift from Magic Leap and a donation from NVIDIA. We want to thank Wenqi Xian, Professor Steve Marschner, and members of Intel Labs for providing insightful feedback for this project.