torch-ngp

A pytorch implementation of instant-ngp, as described in Instant Neural Graphics Primitives with a Multiresolution Hash Encoding.

News: With the CUDA ray marching option for NeRF, we can now:

• converge to a reasonable result in about 1min (50 epochs).
• render a 1920x1080 image in under 1s. (tested on the fox dataset with a TITAN RTX)

For the LEGO dataset, we can reach ~10FPS at 800x800.

(Although the speed is still 2x~5x slower compared to the original implementation.)

SDF	NeRF

Progress

As the official pytorch extension tinycudann has been released, the following implementations can be used as modular alternatives. The performance and speed of these modules are guaranteed to be on-par, and we support using tinycudann as the backbone by the --tcnn flag. Later development will be focused on reproducing the NeRF inference speed.

• Fully-fused MLP
  • basic pytorch binding of the original implementation
• HashGrid Encoder
  • basic pytorch CUDA extension
  • fp16 support
• Experiments
  • SDF
    • baseline
    • better SDF calculation (especially for non-watertight meshes)
  • NeRF
    • baseline
    • ray marching in CUDA.
• Misc.
  • more robust camera (e.g., when rays not intersect with the bounding box)
  • improve performance (e.g., avoid the cat in NeRF forward)

Install

pip install -r requirements.txt

# (optional) install the tcnn backbone
pip install git+https://github.com/NVlabs/tiny-cuda-nn/#subdirectory=bindings/torch

Tested on Ubuntu with torch 1.10 & CUDA 11.3 on TITAN RTX.

Usage

We use the same data format as instant-ngp, e.g., armadillo and fox. Please download and put them under ./data.

First time running will take some time to compile the CUDA extensions.

# SDF experiment
bash scripts/run_sdf.sh

# NeRF experiment (see the shell script for more options)
bash scripts/run_nerf.sh

# use different backbones
python train_nerf.py data/fox/transforms.json --workspace trial_nerf # fp32 mode
python train_nerf.py data/fox/transforms.json --workspace trial_nerf --fp16 # fp16 mode (pytorch amp)
python train_nerf.py data/fox/transforms.json --workspace trial_nerf --fp16 --ff # fp16 mode + FFMLP (this repo's implementation)
python train_nerf.py data/fox/transforms.json --workspace trial_nerf --fp16 --tcnn # fp16 mode + official tinycudann's encoder & MLP

# [NEW] use CUDA to accelerate ray marching 
python train_nerf.py data/fox/transforms.json --workspace trial_nerf --fp16 --ff --cuda_ray # fp16 mode + FFMLP + cuda raymarching

Difference from the original implementation

• Instead of assuming the scene is bounded in the unit box [0, 1] and centered at (0.5, 0.5, 0.5), this repo assumes the scene is bounded in box [-bound, bound], and centered at (0, 0, 0). Therefore, the functionality of aabb_scale is replaced by bound here.
• For the hashgrid encoder, this repo only implement the linear interpolation mode.
• For the voxel pruning in ray marching kernels, this repo doesn't implement the multi-scale density grid (check the mip keyword), and only use one 128x128x128 grid for simplicity. Instead of updating the grid every 16 steps, we update it every epoch, which may lead to slower first few epochs if using --cuda_ray.

Update Logs

• 2.20: cuda raymarching is finally stable now!
• 2.15: add the official tinycudann as an alternative backend.
• 2.10: add cuda_ray, can train/infer faster, but performance is worse currently.
• 2.6: add support for RGBA image.
• 1.30: fixed atomicAdd() to use __half2 in HashGrid Encoder's backward, now the training speed with fp16 is as expected!
• 1.29:
  • finished an experimental binding of fully-fused MLP.
  • replace SHEncoder with a CUDA implementation.
• 1.26: add fp16 support for HashGrid Encoder (requires CUDA >= 10 and GPU ARCH >= 70 for now...).

Acknowledgement

• Credits to Thomas Müller for the amazing tiny-cuda-nn and instant-ngp:

  @misc{tiny-cuda-nn,
      Author = {Thomas M\"uller},
      Year = {2021},
      Note = {https://github.com/nvlabs/tiny-cuda-nn},
      Title = {Tiny {CUDA} Neural Network Framework}
  }
  
  @article{mueller2022instant,
      title = {Instant Neural Graphics Primitives with a Multiresolution Hash Encoding},
      author = {Thomas M\"uller and Alex Evans and Christoph Schied and Alexander Keller},
      journal = {arXiv:2201.05989},
      year = {2022},
      month = jan
  }
  

• The framework of NeRF is adapted from nerf_pl:

  @misc{queianchen_nerf,
      author = {Quei-An, Chen},
      title = {Nerf_pl: a pytorch-lightning implementation of NeRF},
      url = {https://github.com/kwea123/nerf_pl/},
      year = {2020},
  }