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

.. function:: warp._src.lang.quat_twist_angle_signed(axis: vec3f, q: quatf) -> float

   .. hlist::
      :columns: 8

      * Kernel
      * Differentiable

   Return the signed twist angle of ``q`` around ``axis``.
   
   Unlike :func:`quat_twist_angle`, this preserves the sign of the twist, so
   rotations by ``+theta`` and ``-theta`` around ``axis`` return opposite
   values.
   
   The result follows the quaternion branch supplied by ``q``. Since ``q`` and
   ``-q`` represent the same orientation but different quaternion branches,
   they may produce signed angles that differ by ``2*pi``.
   
   :param axis: Twist axis. Expected to be normalized by the caller.
   :param q: Input quaternion in ``(x, y, z, w)`` layout.
   
   :returns: Signed twist angle in radians in ``[-2*pi, 2*pi]``.
   :rtype: float