linefit

linefit is a ground segmentation algorithm for 3D point clouds. This repo we setup a python binding for the original C++ code and push to pypi for easy installation through pip install linefit.

Author: C++ code from Lorenz Wellhausen, nanobind by Qingwen Zhang.

Running on macOS, Windows and Linux, with Python Version >= 3.8.

Available in:

📜 Change Log:

• 2024-07-03: Speed up nanobind np.array <-> std::vector<Eigen:: Vector3d> conversion and also NOMINSIZE in make. Speed difference: 0.1s -> 0.01s. Based on discussion here.
• 2024-02-15: Initial version.

0. Setup

Choose one of the following options to install the package (recommended to use Option A pip install linefit):

Option A: Install from pypi pip install linefit

Option B: Clone this repo and run following to build:

cmake -B build && cmake --build build
pip install .
python3 -c 'import linefit; print("success")'

1. Run the example

After installation, you can run the example by, it will directly show a default effect of demo data.

python example.py

A window will pop up and show the ground segmentation result.

Parameter description

TL;DR: tune the sensor_height to offset the ground point z to 0. Others are optional for better performance. If you are interested in the details, please read the following.

Parameters are set in assets/config.toml

This algorithm works on the assumption that you known the height of the sensor above ground. Therefore, you have to adjust the sensor_height to your robot specifications, otherwise, it will not work.

The default parameters should work on the KITTI dataset.

Ground Condition

• sensor_height Sensor height above ground.
• max_dist_to_line maximum vertical distance of point to line to be considered ground.
• max_slope Maximum slope of a line.
• min_slope Minimum slope of a line.
• max_fit_error Maximum error a point is allowed to have in a line fit.
• max_start_height Maximum height difference between new point and estimated ground height to start a new line.
• long_threshold Distance after which the max_height condition is applied.
• max_height Maximum height difference between line points when they are farther apart than long_threshold.
• line_search_angle How far to search in angular direction to find a line. A higher angle helps fill "holes" in the ground segmentation.

Segmentation

• r_min Distance at which segmentation starts.
• r_max Distance at which segmentation ends.
• n_bins Number of radial bins.
• n_segments Number of angular segments.

Other

• n_threads Number of threads to use.

Acknowledgement & Citation

The original C++ code is from the repo we forked: lorenwel/linefit_ground_segmentation.

The original methods are described in the following paper:

@inproceedings{himmelsbach2010fast,
  title={Fast segmentation of 3d point clouds for ground vehicles},
  author={Himmelsbach, Michael and Hundelshausen, Felix V and Wuensche, H-J},
  booktitle={Intelligent Vehicles Symposium (IV), 2010 IEEE},
  pages={560--565},
  year={2010},
  organization={IEEE}
}

More python binding examples can be found in our other project:

• dufomap: a dynamic awareness mapping framework. Remove dynamic points in a raw map.
• dztimer: a breakout timer for python code.