Function gvr_sys::gvr_get_head_space_from_start_space_rotation

pub unsafe extern fn gvr_get_head_space_from_start_space_rotation(gvr: *const gvr_context,
                                                                  time: gvr_clock_time_point)
                                                                  -> gvr_mat4f

Gets the rotation from start space to head space. The head space is a space where the head is at the origin and faces the -Z direction.

@param gvr Pointer to the gvr instance from which to get the pose. @param time The time at which to get the head pose. The time should be in the future. If the time is not in the future, it will be clamped to now. @return A matrix representation of the rotation from start space (the space where the head was last reset) to head space (the space with the head at the origin, and the axes aligned to the view vector).