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VolRecon

Code of paper 'VolRecon: Volume Rendering of Signed Ray Distance Functions for Generalizable Multi-View Reconstruction' (CVPR 2023)

Project | arXiv

Abstract: The success of the Neural Radiance Fields (NeRF) in novel view synthesis has inspired researchers to propose neural implicit scene reconstruction. However, most existing neural implicit reconstruction methods optimize per-scene parameters and therefore lack generalizability to new scenes. We introduce VolRecon, a novel generalizable implicit reconstruction method with Signed Ray Distance Function (SRDF). To reconstruct the scene with fine details and little noise, VolRecon combines projection features aggregated from multi-view features, and volume features interpolated from a coarse global feature volume. Using a ray transformer, we compute SRDF values of sampled points on a ray and then render color and depth. On DTU dataset, VolRecon outperforms SparseNeuS by about 30% in sparse view reconstruction and achieves comparable accuracy as MVSNet in full view reconstruction. Furthermore, our approach exhibits good generalization performance on the large-scale ETH3D benchmark.

If you find this project useful for your research, please cite:

@misc{ren2022volrecon,
      title={VolRecon: Volume Rendering of Signed Ray Distance Functions for Generalizable Multi-View Reconstruction}, 
      author={Yufan Ren and Fangjinhua Wang and Tong Zhang and Marc Pollefeys and Sabine Süsstrunk},
      journal={CVPR},
      year={2023}
}

Installation

Requirements

• python 3.8
• CUDA 10.2

conda create --name volrecon python=3.8 pip
conda activate volrecon

pip install -r requirements.txt

Reproducing Sparse View Reconstruction on DTU

• Download pre-processed DTU dataset. The dataset is organized as follows:

root_directory
├──cameras
    ├── 00000000_cam.txt
    ├── 00000001_cam.txt
    └── ...  
├──pair.txt
├──scan24
├──scan37
      ├── image               
      │   ├── 000000.png       
      │   ├── 000001.png       
      │   └── ...                
      └── mask                   
          ├── 000.png   
          ├── 001.png
          └── ...                

Camera file cam.txt stores the camera parameters, which includes extrinsic, intrinsic, minimum depth and depth range interval:

extrinsic
E00 E01 E02 E03
E10 E11 E12 E13
E20 E21 E22 E23
E30 E31 E32 E33

intrinsic
K00 K01 K02
K10 K11 K12
K20 K21 K22

DEPTH_MIN DEPTH_INTERVAL

pair.txt stores the view selection result. For each reference image, 10 best source views are stored in the file:

TOTAL_IMAGE_NUM
IMAGE_ID0                       # index of reference image 0 
10 ID0 SCORE0 ID1 SCORE1 ...    # 10 best source images for reference image 0 
IMAGE_ID1                       # index of reference image 1
10 ID0 SCORE0 ID1 SCORE1 ...    # 10 best source images for reference image 1 
...

• In script/eval_dtu.sh, set DATASET as the root directory of the dataset, set OUT_DIR as the directory to store the rendered depth maps. CKPT_FILE is the path of the checkpoint file (default as our model pretrained on DTU). Run bash eval_dtu.sh on GPU. By Default, 3 images (--test_n_view 3) in image set 0 (--set 0) are used for testing.
• In tsdf_fusion.sh, set ROOT_DIR as the directory that stores the rendered depth maps. Run bash tsdf_fusion.sh on GPU to get the reconstructed meshes in mesh directory.
• For quantitative evaluation, download SampleSet and Points from DTU's website. Unzip them and place Points folder in SampleSet/MVS Data/. The structure looks like:

SampleSet
├──MVS Data
      └──Points

• Following SparseNeuS, we clean the raw mesh with object masks by running:

python evaluation/clean_mesh.py --root_dir "PATH_TO_DTU_TEST" --n_view 3 --set 0

• Get the quantitative results by running evaluation code:

python evaluation/dtu_eval.py --dataset_dir "PATH_TO_SampleSet_MVS_Data"

• Note that you can change --set in eval_dtu.sh and --set during mesh cleaning to use different image sets (0 or 1). By default, image set 0 is used. The average chamfer distance of sets 0 and 1 is what we reported in Table 1.

Evaluation on Custom Dataset

We provide some helpful scripts for evaluation on custom datasets, which consists of a set of images. As discussed in the limitation section, our method is not suitable for very large-scale scenes because of the coarse global feature volume. The main steps are as follows:

• Run COLMAP for sparse reconstruction.
• Use colmap_input.py to convert COLMAP's sparse reconstruction results into the similar format as the datasets that we use. The dataset should be organized as:

root_directory
├──scene_name1
├──scene_name2 
      ├── images                 
      │   ├── 00000000.jpg       
      │   ├── 00000001.jpg       
      │   └── ...                
      ├── cams                   
      │   ├── 00000000_cam.txt   
      │   ├── 00000001_cam.txt   
      │   └── ...                
      └── pair.txt  

This step is mainly to get camera files and view selection (pair.txt). As discussed previously, the view selection will pick out best source views for a reference view, which also helps to further reduce the volume size. The camera file stores the camera parameters, which includes extrinsic, intrinsic, minimum depth and maximum depth:

extrinsic
E00 E01 E02 E03
E10 E11 E12 E13
E20 E21 E22 E23
E30 E31 E32 E33

intrinsic
K00 K01 K02
K10 K11 K12
K20 K21 K22

DEPTH_MIN DEPTH_MAX

• The file code/dataset/general_fit.py is the dataset loader. The parameter self.offset_dist is the distance offset w.r.t. the reference view to generate a virtual viewpoint for rendering, which can be adjusted (set to 25mm by default).
• Use script/eval_general.sh for image and depth rendering.

Training on DTU

• Download pre-processed DTU's training set and Depths_raw (both provided by MVSNet). Then organize the dataset as follows:

root_directory
├──Cameras
├──Rectified
└──Depths_raw

• In train_dtu.sh, set DATASET as the root directory of dataset; set LOG_DIR as the directory to store the checkpoints.

• Train the model by running bash train_dtu.sh on GPU.

Acknowledgement

Part of the code is based on SparseNeuS and IBRNet.