Make it Dense: Self-Supervised Geometric Scan Completion of Sparse 3D LiDAR Scans in Large Outdoor Environments

This repository contains the implementation of the following publication:

@article{vizzo2022ral,
  author  = {I. Vizzo and B. Mersch and R. Marcuzzi and L. Wiesmann and J. Behley and C. Stachniss},
  title   = {{Make it Dense: Self-Supervised Geometric Scan Completion of Sparse 3D LiDAR Scans in Large Outdoor Environments}},
  journal = {IEEE Robotics and Automation Letters (RA-L)},
  year    = 2022
}

Overview

A TSDF-based surface model from a single 16-beam LiDAR scan (left) turned into a denser, completed TSDF-based surface model (right) by the learning-based approach proposed in this paper.

Overview of our approach. We first generate a TSDF volume of a single scan. We then apply our geometric scan completion network in a strided fashion, such that missing values are added to the single-scan TSDF, giving a more complete TSDF volume. The predicted TSDF values are then used to update the global TSDF representation using a weighting term η to avoid integrating the same observation twice into the map.

Table of Contents

• Installation
  • Instal OpenVDB
  • Install vdb_to_numpy
  • Install vdbfusion
  • Install make_it_dense
  • Install torch
• Data
• Training
  • Precache
  • Inspecting cached models
  • Train
• Testing
  • Single Scan Test
  • Test Refusion Pipeline

Installation

Instal OpenVDB

You will need to install the library from source, I would also reccomend to use my own fork until I found a solution for #1096, if you have all dependencies installed just:

git clone https://github.com/nachovizzo/openvdb.git -b nacho/fix_background_inactive \
  && cd openvdb \
  && mkdir build && cd build \
  && cmake -DOPENVDB_BUILD_PYTHON_MODULE=ON -DUSE_NUMPY=ON .. \
  && sudo make -j$(nproc) all install 

Install vdb_to_numpy

We need this small library to convert our VDB volumes to numpy arrays, and use the data for training.

git clone https://github.com/PRBonn/vdb_to_numpy \
    && cd vdb_to_numpy \
    && pip install .

Install vdbfusion

We need to install this library from the source, not from the pip package. All the details are in the INSTALL.md, but basically:

git clone https://github.com/PRBonn/vdbfusion.git \
    && cd vdbfusion \
    && pip install .

Install make_it_dense

On the root of this repository do pip install .

Install torch

I do not enforce any particular version of PyTorch, make sure it is not extremely old and that it has CUDA support

Data

We use the KITTI Odometry dataset, download it and place it in the data/ folder. If you don't want to do so, you can also change the path in the config/kitti.yaml file.

Training

To reproduce the results of the paper, you can use sequence 07 from KITTI to train the network

Precache

To speed up training it is recommended to first cache all the vdb-grids, for there is a handy script that will do it for you:

./apps/precache.py -s 07

This will take some time but will save a lot in the future

Inspecting cached models

To make sure everything is OK I would advise you to also inspect the VDB models you generate for training:

./apps/dump_training_data.py -s 07

This will output all the vdbs that will be used for training following this structure:

├── gt
│   ├── gt_tsdf_10
│   ├── gt_tsdf_20
│   └── gt_tsdf_40
└── tsdf

To visually inspect the models, go to one directory and run vdb_view *.vdb, using the arrows you can navigate the OpenVDB visualizer and see all the models.

Train

Training should now be straight-forward:

./apps/train.py --config config/kitti.yaml

Testing

To test the network you can use your trained model or use the default one in models. There are 2 entry points to test the network:

Single Scan Test

To test how the network behaves with just 1 scan (use any point-cloud you wish):

./apps/test_scan.py --cuda  $DATASETS/kitti-odometry/dataset/sequences/00/velodyne/000000.bin 

Test Refusion Pipeline

To test the full pipeline when using a 16-beam LiDAR you can use the following command:

./apps/refusion_pipeline.py --sequence 00 -n 30 --visualize