/// <summary>
/// Mirrors a heading rotation (z-forward) across a plane
/// </summary>
/// <param name="origHeading">the rotation to mirror</param>
/// <param name="planeNormal">the normal of the plane across which to mirror the rotation</param>
/// <returns>the mirrored rotation</returns>
static public Quaternion MirrorHeading(Quaternion origHeading, Vector3 planeNormal)
{
	Vector3 origHeadingVec = origHeading * Vector3.forward;
	Vector3 origUpVec = origHeading * Vector3.up;

	if (Vector3.Dot(origHeadingVec, planeNormal) < 0.0f) { planeNormal = -planeNormal; }
	Vector3 newHeadingVec = MirrorVector(origHeadingVec, planeNormal);
	Vector3 newUpVec = MirrorVector(origUpVec, planeNormal);

	return Quaternion.LookRotation(newHeadingVec, newUpVec);
}
#endregion

#region Vector Math

static public Vector3 MirrorVector(Vector3 vector, Vector3 normal)
{
	Vector3 flipVec = normal * Vector3.Dot(vector, normal); // (project the vector onto the normal, then...)
	return vector - (2f * flipVec); // (subtracting 1x gets you v on the plan, subtracting 2x gets you the mirror)
}