//finder s, med hensyntagende til de periodiske grænse betingelser hvor s er A->B
void getS(struct position A, struct position B, struct float3 *s)
{
	getR(A, B, s);
	s->x = s->x - floor((s->x + sysSizeHalf) / sysSize) * sysSize;
 
	s->y = s->y - floor((s->y + sysSizeHalf) / sysSize) * sysSize;
 
	s->z = s->z - floor((s->z + sysSizeHalf) / sysSize) * sysSize;
}
 
void getR(struct position A, struct position B, struct float3 *r)
{
	r->x = B.x - A.x;
	r->y = B.y - A.y;
	r->z = B.z - A.z;
	return;
}