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Abstract: Neural Radiance Field (NeRF) has achieved remarkable results in synthesizing photo-realistic novel views with implicit function representations. However, NeRF significantly degrades when only a few views are available. To address this problem, existing few-shot NeRF methods impose sparsity and continuity regularizations on geometry (e.g., density and depth), or exploit high-level semantics to guide the learning of NeRF. Although these methods reduce degradation in few-shot scenarios, they still struggle to synthesize photo-realistic novel views due to insufficient 3D constraints. To complement the lack of 3D information, we present a new Sparse-view NeRF (SparseNeRF) framework that effectively exploits robust depth priors from a large pre-trained depth model. Since the depth estimation of large pre-trained depth models is coarse, we propose a local depth ranking constraint on NeRF such that the expected depth ranking of the NeRF is consistent with that of the pre-trained depth model in local patches. To preserve spatial continuity of the estimated depth of NeRF, we further propose a spatial continuity constraint such that the expected depth continuity of NeRF is consistent with that of the pre-trained depth model. With the distilled depth priors of large pre-trained depth models, SparseNeRF outperforms all of the state-of-the-art few-shot NeRF methods. Extensive experiments on the LLFF and DTU benchmarks show the effectiveness and superiority of SparseNeRF. Code and models will be released.

1. Prerequisites

• Linux or macOS
• Python 3.6.13
• NVIDIA GPU + CUDA cuDNN(10.1)
• OpenCV

2. Installation

We recommend using the virtual environment (conda) to run the code easily.

git clone https://github.com/Wanggcong/SparseNeRF.git
cd SparseNeRF

conda create -n sparsenerf python=3.6.13
conda activate sparsenerf
pip install -r requirements.txt

Download jax+cuda (jaxlib-0.1.68+cuda101-cp36) wheels from this link

wget https://storage.googleapis.com/jax-releases/cuda101/jaxlib-0.1.68+cuda101-cp36-none-manylinux2010_x86_64.whl

Install the downloaded file:

pip install jaxlib-0.1.68+cuda101-cp36-none-manylinux2010_x86_64.whl

Install pytorch and related packages for pretrained depth models

conda install pytorch==1.7.1 torchvision==0.8.2 torchaudio==0.7.2 cudatoolkit=10.1 -c pytorch
pip install timm

Install ffmpeg for composing videos

pip install imageio-ffmpeg

3. Dataset

Download DTU dataset

• Download the DTU dataset from the official website, "Rectified (123 GB)" and "SampleSet (6.3 GB)"
• Data: extract "Rectified (123 GB)"
• Poses: extract "SampleSet/MVS\ Data/Calibration/cal18/" from "SampleSet (6.3 GB)"
• Masks: download masks (used for evaluation only) from this link

Download LLFF dataset

• Download LLFF from the official download link.

Pre-process datasets

• Get depth maps
• For both LLFF and DTU, please set the variables $root_path, $benchmark, and $dataset_id in get_depth_map.sh, and run:

sh scripts/get_depth_map.sh

4. Training

4.1 Training on LLFF

Please set the variables in train_llff3.sh, and run:

sh scripts/train_llff3.sh

4.2 Training on DTU

Please set the variables in train_dtu3.sh, and run:

sh scripts/train_dtu3.sh

5. Test

5.1 Evaluate PSNR and SSIM

Please set the variables (the same as train_llff3.sh and train_dtu3.sh) in eval_llff3.sh or eval_dtu3, and run:

sh scripts/eval_llff3.sh

or

sh scripts/eval_dtu3.sh

5.2 (optional) Render videos

Please set the variables (the same as train_llff3.sh and train_dtu3.sh) in render_video_llff3.sh or render_video_dtu3, and run:

sh scripts/render_video_llff3.sh

or

sh scripts/render_video_dtu3.sh

5.3 (optional) Compose videos

Please set the variables in get_video.sh, and run:

sh get_video.sh

5.4 (optional) Tensorboard for visualizing training if necessary.

tensorboard --logdir=./out/xxx/ --port=6006

If it raises errors, see Q2 of FQA

6. To-Do

• Training code
• Inference model
• Clean Code
• Colab Demo

7. Citation

If you find this useful for your research, please cite the our paper.

@inproceedings{wang2022sparsenerf,
   author    = {Wang, Guangcong and Chen, Zhaoxi and Loy, Chen Change and Liu, Ziwei},
   title     = {SparseNeRF: Distilling Depth Ranking for Few-shot Novel View Synthesis},
   booktitle = {Under review},   
   year      = {2022},
  }

or

Guangcong Wang, Zhaoxi Chen, Chen Change Loy, and Ziwei Liu. SparseNeRF: Distilling Depth Ranking for Few-shot Novel View Synthesis, Under review.

8. Related Links

RegNeRF: Regularizing Neural Radiance Fields for View Synthesis from Sparse Inputs, CVPR, 2022

StyleLight: HDR Panorama Generation for Lighting Estimation and Editing, ECCV 2022.

Relighting4D: Neural Relightable Human from Videos, ECCV 2022

9. Acknowledgments

This code is based on the RegNeRF and DPT codebases.

10. FAQ

We will summarize frequently asked questions at this link FAQ.