Bulge (optional; default is 0). The bulge is the tangent of one fourth the included angle for an arc segment, made negative if the arc goes clockwise from the start point to the endpoint. A bulge of 0 indicates a straight segment, and a bulge of 1 is a semicircle
tan (90/4) = tan (22.5 deg) = 0.414
tan (180/4) = tan (45 deg) = 1