warp.quat\_twist\_angle
=======================

.. currentmodule:: warp._src.lang

.. function:: quat_twist_angle(axis: vec3f, q: quatf) -> float

   .. wp-function-tags::
      :kernel: true
      :python: true
      :differentiable: true
      :source: https://github.com/NVIDIA/warp/blob/release-1.19/warp/_src/math.py#L172-L194

   Return the unsigned twist magnitude in radians of ``q`` around ``axis``.
   
   This discards the sign of the twist, so rotations by ``+theta`` and
   ``-theta`` around ``axis`` return the same value. Use
   :func:`quat_twist_angle_signed` when the direction of rotation around
   ``axis`` matters.
   
   :param axis: Twist axis, with unit length.
   :param q: Rotation quaternion.
   
   :returns: Unsigned twist angle in radians, in ``[0, pi]`` if ``q[3] >= 0`` and
             in ``(pi, 2*pi]`` otherwise, so ``q`` and ``-q`` can return different
             angles even though they represent the same rotation. It is unspecified
             when ``q`` is a rotation of 180 degrees about an axis perpendicular to
             ``axis``.
   :rtype: float