pytransform3d.rotations.compact_axis_angle

pytransform3d.rotations.compact_axis_angle(a)

Compute 3-dimensional axis-angle from a 4-dimensional one.

In the 3-dimensional axis-angle representation, the 4th dimension (the rotation) is represented by the norm of the rotation axis vector, which means we map \(\left( \hat{\boldsymbol{\omega}}, \theta \right)\) to \(\boldsymbol{\omega} = \theta \hat{\boldsymbol{\omega}}\).

This representation is also called rotation vector or exponential coordinates of rotation.

Parameters:

aarray-like, shape (4,)

Axis of rotation and rotation angle: (x, y, z, angle).

Returns:

aarray, shape (3,)

Axis of rotation and rotation angle: angle * (x, y, z) (compact representation).