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Grad-PU

arXiv | Project Page | Code

This is the official PyTorch implementation of our paper "Grad-PU: Arbitrary-Scale Point Cloud Upsampling via Gradient Descent with Learned Distance Functions" (CVPR 2023).

Abstract

Most existing point cloud upsampling methods have roughly three steps: feature extraction, feature expansion and 3D coordinate prediction. However, they usually suffer from two critical issues: (1) fixed upsampling rate after one-time training, since the feature expansion unit is customized for each upsampling rate; (2) outliers or shrinkage artifact caused by the difficulty of precisely predicting 3D coordinates or residuals of upsampled points. To adress them, we propose a new framework for accurate point cloud upsampling that supports arbitrary upsampling rates. Our method first interpolates the low-res point cloud according to a given upsampling rate. And then refine the positions of the interpolated points with an iterative optimization process, guided by a trained model estimating the difference between the current point cloud and the high-res target. Extensive quantitative and qualitative results on benchmarks and downstream tasks demonstrate that our method achieves the state-of-the-art accuracy and efficiency.

Installation

  • Install the following packages
python==3.7.11
torch==1.7.1
CUDA==11.0
numpy==1.21.2
open3d==0.9.0.0
einops==0.3.2
scikit-learn==1.0.1
tqdm==4.62.3
h5py==3.6.0
  • Install the built-in libraries
cd models/Chamfer3D
python setup.py install
cd ../pointops
python setup.py install
  • Compile the evaluation_code for metric calculation (optional)

To calculate the CD, HD and P2F metrics, you need to install the CGAL library (please follow the PU-GAN repo) and virtual environment of PU-GCN (please follow the PU-GCN repo) first. And then you also need to compile the evaluation_code folder.

cd evaluation_code
bash compile.sh

These commands are tested on an ubuntu 16.04 system.

Data Preparation

First download the PU-GAN (train set, test mesh) and PU1K datasets, then unzip them and put them into the data/PU-GAN/train folder, data/PU-GAN folder and data/PU1K folder repestively. Since the PU-GAN dataset only provides mesh files for test, we first generate test point clouds by Poisson disk sampling.

  • PU-GAN test point cloud generation
# 4X, generated files will be saved at ./data/PU-GAN/test_pointcloud/input_2048_4X by default
python prepare_pugan.py --input_pts_num 2048 --gt_pts_num 8192
# 16X, generated files will be saved at ./data/PU-GAN/test_pointcloud/input_2048_16X by default
python prepare_pugan.py --input_pts_num 2048 --gt_pts_num 32768
# 5X, generated files will be saved at ./data/PU-GAN/test_pointcloud/input_2048_5X by default
python prepare_pugan.py --input_pts_num 2048 --gt_pts_num 10240

where input_pts_num denotes the point number of input low-res point cloud, gt_pts_num denotes the point number of ground truth high-res point cloud, and you can modify these two arguments to obtain various upsampling rates or input sizes.

You can also use the noise_level argument to generate the noisy low-res input.

# 4X, noise_level=0.01, generated files will be saved at ./data/PU-GAN/test_pointcloud/input_2048_4X_noise_0.01 by default
python prepare_pugan.py --input_pts_num 2048 --gt_pts_num 8192 --noise_level 0.01

The final file structure of data folder is shown as follow:

data  
├───PU-GAN
│   ├───test # test mesh file
│   ├───test_pointcloud # generated test point cloud file
│   │     ├───input_2048_16X
│   │     ├───input_2048_4X
│   │     ├───input_2048_4X_noise_0.01
│   │     ...
│   └───train
│   │     └───PUGAN_poisson_256_poisson_1024.h5
└───PU1K
│   ├───test
│   │     ├───input_1024
│   │     ├───input_2048
│   │     ...
│   └───train
│   │     └───pu1k_poisson_256_poisson_1024_pc_2500_patch50_addpugan.h5

Quick Start

We have provided the pretarined models in the pretrained_model folder, so you can directly use them to reproduce the results.

  • PU-GAN
# 4X, upsampled point clouds will be saved at ./pretrained_model/pugan/test/4X
python test.py --dataset pugan --test_input_path ./data/PU-GAN/test_pointcloud/input_2048_4X/input_2048/ --ckpt_path ./pretrained_model/pugan/ckpt/ckpt-epoch-60.pth --save_dir 4X --up_rate 4
# 16X, upsampled point clouds will be saved at ./pretrained_model/pugan/test/16X
python test.py --dataset pugan --test_input_path ./data/PU-GAN/test_pointcloud/input_2048_16X/input_2048/ --ckpt_path ./pretrained_model/pugan/ckpt/ckpt-epoch-60.pth --save_dir 16X --up_rate 16
# 5X, upsampled point clouds will be saved at ./pretrained_model/pugan/test/5X
python test.py --dataset pugan --test_input_path ./data/PU-GAN/test_pointcloud/input_2048_5X/input_2048/ --ckpt_path ./pretrained_model/pugan/ckpt/ckpt-epoch-60.pth --save_dir 5X --up_rate 5

The upsampled point clouds are saved at ./pretrained_model/pugan/test/save_dir. Then you can utilize the following commands to calculate metrics.

# take 4X upsampled results for example
cd evaluation_code
python write_eval_script.py --dataset pugan --upsampled_pcd_path ../pretrained_model/pugan/test/4X/
bash eval_pugan.sh

Later you need to shift to the virtual environment and code folder of PU-GCN, and then run the evaluate.py script of PU-GCN repo.

Note: the evaluate.py script isn't compatible with our environment.

python evaluate.py --pred path_to_upsampled_point_clouds --gt path_to_ground_truth_high-res_point_clouds --save_path calculated_metrics_save_path

You should fill the pred, gt and save_path arguments of evaluate.py script accordingly. And finally you can get the evaluation.csv and finalresult.text files in the save_path folder.

  • PU1K
# 4X, upsampled point clouds will be saved at ./pretrained_model/pu1k/test/4X
python test.py --dataset pu1k --test_input_path ./data/PU1K/test/input_2048/input_2048/ --ckpt_path ./pretrained_model/pu1k/ckpt/ckpt-epoch-60.pth --save_dir 4X --up_rate 4

Similarly, you can utilize the following commands to calculate the metrics for the PU1K dataset.

# take 4X upsampled results for example
cd evaluation_code
python write_eval_script.py --dataset pu1k --upsampled_pcd_path ../pretrained_model/pu1k/test/4X
bash eval_pu1k.sh
# first shift to the virtual environment of PU-GCN, and then run the evaluate.py script 
python evaluate.py --pred path_to_upsampled_point_clouds --gt path_to_ground_truth_high-res_point_clouds --save_path calculated_metrics_save_path

You should fill the pred, gt and save_path arguments of evaluate.py script accordingly. And finally you can get the evaluation.csv and finalresult.text files in the save_path folder.

Note: If you want to use different input files, checkpoints, upsampling rates, etc, you should modify those aforementioned arguments accordingly.

Training

If you want to train our model by yourself, you can try the following commands.

  • PU-GAN
python train.py --dataset pugan
  • PU1K
python train.py --dataset pu1k

The checkpoints and log files will be saved at ./output/experiment_id/ckpt and ./output/experiment_id/log folders respectively. And for evaluation, you can refer to the Quick Start section.

Acknowledgments

Our code is built upon the following repositories: PU-GCN, PU-GAN and PAConv. Thanks for their great work.

Citation

If you find our project is useful, please consider citing us:

@InProceedings{He_2023_CVPR,
    author    = {He, Yun and Tang, Danhang and Zhang, Yinda and Xue, Xiangyang and Fu, Yanwei},
    title     = {Grad-PU: Arbitrary-Scale Point Cloud Upsampling via Gradient Descent with Learned Distance Functions},
    booktitle = {Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
    year      = {2023}
}