public static int which_side_pn(double x0, double y0, double nx, double ny, double px, double py){
		int side;
		double dot = nx*(px - x0) + ny*(py - y0);

		if(dot < -ACCY)
			side = PLANE_INSIDE;
		else if(dot > ACCY)
			side = PLANE_OUTSIDE;
		else 
			side = ON_PLANE;
		return side;
	}