public void GetDeltaA(float deltaC)
{
Vector2 va = ap.position - m.position;
Vector2 vb = bp.position - m.position;
//float zunit = FVector2.Cross(va,vb);
float zunit = deltaC;
Vector2 deltaA = FVector2.CrossUnitZ(va, zunit) * Mathf.Abs(deltaC) / 2f;
Vector2 deltaB = FVector2.CrossUnitZ(vb, -zunit) * Mathf.Abs(deltaC) / 2f;
DebugExtension.DebugArrow(ap.position, deltaA);
DebugExtension.DebugArrow(bp.position, deltaB);
}