# Dxf Polyline Bulge

• The bulge is the tangent of 1/4 of the included angle for the arc between the selected vertex and the next vertex in the polyline's vertex list. A negative bulge value indicates that the arc goes clockwise from the selected vertex to the next vertex. A bulge of 0 indicates a straight segment, and a.
• Polyline (don’t confuse with 2D polyline and 3D polyline) Vertices (Bulge attribute is supported) Draw color. Saved as DWG/DXF Element.
• The bulge factor is located with group code 42. If a segment does not have an arc, the bulge factor is zero. When there is an arc in the segment, the value seen with group code 42 is the result of calculating the tangent value of one quarter of the included angle.

## How do use the 'Bulge' from a polyline The curvature of a Polyline Arc segment is defined using a quantity known as bulge. The curve from the straight line (chord) joining the two vertices of the segment. Mac parallel free. It is defined as the ratio of the arc sagitta (versine) to half the length of the chord between the two vertices; this ratio is equal to the tangent of a quarter of the included arc. Polylines: Radius-Bulge Turnaround The dxf representation of LWPOLYLINEs represents arcs using the end points of the arc and a bulge factor which is the tangent of a quarter of the central angle of the arc (see this previous post). We want to interchange between the radius and the bulge factor (both ways). Let's pull up the earlier diagram.

## How do use the 'Bulge' from a polyline

Hi,  I'm trying to write a small export utility in VB to write the coordinates of a polyline to a text file and I'm tripping on the the bulge.
On a polyline, Autocad reports coordinates and a Bulge on a vertex. I need to convert this to an arc item, and my application supports a constructor with the following arguments:
1. Centre of arc

## Dxf Polyline Bulge

2. Start angle 3. End Angle