MortonNet: Self-Supervised Learning of Local Features in 3D Point Clouds

MortonNet is a self-supervised approach for point cloud processing. MortonNet learns local geometric features for each point. Given a point cloud, our approach creates sequences for each point. These sequences are based on the popular Morton order. With a sequence of N points, MortonNet uses the first N - 1 points and learns to predict the last point. We show how to use MortonNet with the S3DIS Dataset.

Data

We download and prepare the data using the tools provided by Engelmann et. al. available here. To download the dataset fill in this form. Next we process the data and convert to npy files for processing. This code is from Engelmann et. al.:

python prepare_s3dis.py --input_dir path/to/dataset --output_dir path/to/output

Installation

All the required packages are in environment.yml. If you use conda, you can directly run:

conda env create -f environment.yml

If you prefer to use pip or any other alternative, you can create your own requirements file using the packages and versions provided. This code was tested with Python 3.6 in Ubuntu 16.04, running CUDA 9.0 and cuDNN 7.4.1. All the package versions are available in the environment file.

Computing Sequences

Before training MortonNet, you have to compute the sequences to feed in the self-supervised training scheme. To create sequences, run the following:

python tools/create_sequences.py --root_dir path/to/dataset --out_dir path/to/save.dir --phase train/valid/test

Note that the path/to/dataset here corresponds to the path with the npy files. By default this will compute sequences for all the available files. You can specify a file id using the argument --data_idx. For more information about available commands run the --help or -h options.

Training MortonNet

Once the sequences are precomputed, you can train MortonNot with:

python train.py --root_dir path/to/sequences --model_dir path/to/checkpoint/save

There are different ways to configure MortonNet parameters. Possible configurations are in tools/config.py. If you create your own config, you can load it using argument --config_type. You can also specify other parameters like using multi GPUs, batch size, and others. For a full list run the --help or -h options.

Computing features

You can use the trained MortonNet to compute features for any point cloud dataset. The features of every sequence come from the last hidden state of the RNN. Since every point gets 5 sequences during sequence computation, we can merge these features in different ways. We output all 5 features for each point, which can later be concatenated or pooled. To compute features run:

python compute_features.py --root_dir path/to/sequences --best_path path/to/mortonnet/model --out_dir path/to/save/features

Citation

If you find our work helpful, please cite our paper.

@misc{thabet2019mortonnet,
    title={MortonNet: Self-Supervised Learning of Local Features in 3D Point Clouds},
    author={Ali Thabet and Humam Alwassel and Bernard Ghanem},
    year={2019},
    eprint={1904.00230},
    archivePrefix={arXiv},
    primaryClass={cs.CV}
}