[BUG report] matrix_to_euler_angles [arg: degrees]

Omniverse Isaac Sim
1

Isaac Sim Version

4.2.0

Isaac Lab Version (if applicable)

1.2

Operating System

Ubuntu 20.04

in “_isaac_sim/exts/omni.isaac.core/omni/isaac/core/utils/rotations.py” has the following funcion :

matrix_to_euler_angles(mat: np.ndarray, degrees: bool = False, extrinsic: bool = True) → np.ndarray

but the argument “degrees” will not work, when it works out pitch = ± pi / 2

2

Could you share a minimal reproducible example that demonstrates the problem? This will greatly assist in diagnosing and resolving the issue.

3

Hi, I think it’s obviously. In the source code:

def matrix_to_euler_angles(mat: np.ndarray, degrees: bool = False, extrinsic: bool = True) -> np.ndarray:
    """Convert rotation matrix to Euler XYZ extrinsic or intrinsic angles.

    Args:
        mat (np.ndarray): A 3x3 rotation matrix.
        degrees (bool, optional): Whether returned angles should be in degrees.
        extrinsic (bool, optional): True if the rotation matrix follows the extrinsic matrix
                   convention (equivalent to ZYX ordering but returned in the reverse) and False if it follows
                   the intrinsic matrix conventions (equivalent to XYZ ordering).
                   Defaults to True.

    Returns:
        np.ndarray: Euler XYZ angles (intrinsic form) if extrinsic is False and Euler XYZ angles (extrinsic form) if extrinsic is True.
    """
    if extrinsic:
        if mat[2, 0] > _POLE_LIMIT:
            roll = np.arctan2(mat[0, 1], mat[0, 2])
            pitch = -np.pi / 2
            yaw = 0.0
            return np.array([roll, pitch, yaw])

        if mat[2, 0] < -_POLE_LIMIT:
            roll = np.arctan2(mat[0, 1], mat[0, 2])
            pitch = np.pi / 2
            yaw = 0.0
            return np.array([roll, pitch, yaw])

        roll = np.arctan2(mat[2, 1], mat[2, 2])
        pitch = -np.arcsin(mat[2, 0])
        yaw = np.arctan2(mat[1, 0], mat[0, 0])
        if degrees:
            roll = math.degrees(roll)
            pitch = math.degrees(pitch)
            yaw = math.degrees(yaw)
        return np.array([roll, pitch, yaw])
    else:
        if mat[0, 2] > _POLE_LIMIT:
            roll = np.arctan2(mat[1, 0], mat[1, 1])
            pitch = np.pi / 2
            yaw = 0.0
            return np.array([roll, pitch, yaw])

        if mat[0, 2] < -_POLE_LIMIT:
            roll = np.arctan2(mat[1, 0], mat[1, 1])
            pitch = -np.pi / 2
            yaw = 0.0
            return np.array([roll, pitch, yaw])
        roll = -math.atan2(mat[1, 2], mat[2, 2])
        pitch = math.asin(mat[0, 2])
        yaw = -math.atan2(mat[0, 1], mat[0, 0])

        if degrees:
            roll = math.degrees(roll)
            pitch = math.degrees(pitch)
            yaw = math.degrees(yaw)
        return np.array([roll, pitch, yaw])

if pitch = ± pi / 2, the function will directly return, and will not go to the “if degrees” branch.