question: public double signed_distance ( PlaPointFloat p_point ) { double dx = point_b . v_x - point_a . v_x ; double dy = point_b . v_y - point_a . v_y ; double det = dy * ( p_point . v_x - point_a . v_x ) - dx * ( p_point . v_y - point_a . v_y ) ; double length = Math . sqrt ( dx * dx + dy * dy ) ; return det / length ; }
target:  Returns the signed distance of this line from p_point. The result will be positive, if the line is on the left of p_point, else negative.