rotate_coords.osl

shader rotate_coords
  (
    point In = P,
    vector Axis = vector(0, 0, 1),
    float Angle = 0,
    point Origin = point(0, 0, 0),
    output point Out = P
  )
  /* simpler alternative to Blender’s Vector-Mapping node
    that only does rotation. */
  {
    float wq = cos(Angle / 2);
    vector vq = sin(Angle / 2) * normalize(Axis);
  /* [vq, wq] is now the rotation quaternion */
    vector v1 = cross(vq, In - Origin) + wq * (In - Origin) + vq;
    float w1 = wq - dot(In - Origin, vq);
    Out = cross(vq, v1) + wq * v1 - w1 * vq + Origin;
  } /*rotate_coords*/