LieGroupsPy

Functions for the Lie Algebra group SE(2) and SE(3)

$$ SE(2) = \begin{bmatrix} R_{11} & R_{12} & t_1 \\ R_{21} & R_{22} & t_2 \\ 0 & 0 & 1 \end{bmatrix} $$

where:

• ( $\mathbf{R} \in SO(2) $) is the rotation matrix.
• ( $\mathbf{t} \in \mathbb{R}^2 $) is the translation vector.

$$ SE(3) = \begin{bmatrix} R_{11} & R_{12} & R_{13} & t_1 \\ R_{21} & R_{22} & R_{23} & t_2 \\ R_{31} & R_{32} & R_{33} & t_3 \\ 0 & 0 & 0 & 1 \end{bmatrix} $$

where:

• ( $\mathbf{R} \in SO(3) $) is the rotation matrix.
• ( $\mathbf{t} \in \mathbb{R}^3 $) is the translation vector.

This representation is commonly used in robotics and computer vision for rigid body transformations.

Install

To install the library run: pip install lie_groups_py

Development

0. Install Poetry
1. make init to create the virtual environment and install dependencies
2. make format to format the code and check for errors
3. make test to run the test suite
4. make clean to delete the temporary files and directories
5. poetry publish --build to build and publish to https://pypi.org/project/lie_groups_py/

Usage

"""Basic docstring for my module."""

import matplotlib.pyplot as plt
import numpy as np
from loguru import logger

from lie_groups_py.se3 import SE3, interpolate_se3


def main() -> None:
    """Run a simple demonstration."""
    pose_0 = SE3(
        xyz=np.array([0.0, 0.0, 0.0]),
        rot=np.eye(3),
    )
    logger.info(pose_0)

    pose_1 = SE3(
        xyz=np.array([[2.0], [2.0], [8.0]]),
        yaw_pitch_roll=(np.pi / 2, np.pi / 4, np.pi / 8),
    )

    pose_interp = interpolate_se3(pose_0, pose_1, t=0.5)

    # plot the results
    fig = plt.figure()
    ax = fig.add_subplot(111, projection="3d")
    pose_0.plot(ax)
    pose_1.plot(ax)
    pose_interp.plot(ax)
    plt.axis("equal")
    ax.set_xlabel("x-axis")
    ax.set_ylabel("y-axis")
    ax.set_zlabel("z-axis")
    plt.tight_layout()
    plt.show()


if __name__ == "__main__":
    main()