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## #351 Create polyline from existing segments bug

open-accepted
nobody
5
2013-02-08
2012-09-17
krzych
No

I want to create polyline from existing segments.
Segments are like in attached dxf. One is 360 degree arc second is line which endpoint is snapped to arc endpoint.
When I try to create polyline and select line as entity arc disappears.
When I try to create it and select arc as entity polyline is created but arc moves and appears in different position. It's coordinates changes.

## Discussion

• krzych
2012-09-17

Attachments

• krzych
2012-09-17

It also fails to create offset for case attached in dxf.

• Rallaz
2012-09-19

This is not a bug.

The real problem is "360 degrees arc is not allowed"
for work you need split the arc in two pieces.

A polyline are a sequence of vertex with "bulge".
Without bulge are lines with it arcs, and bulge are:
tangent of ( included arc / 4 ), then an 180 degrees arc have a bulge of:
tan(180/4) = tan(45)= 1 => Ok.
360 degrees arc: tan(360/90)= tan(90) = infinite.
A computer only reaches to MAXDOUBLE that is much less than infinite.

The other problem are:
center are in a perpendicular of line from start to end vertex
because v1 == v2 chord length is 0, impeding calculate the correct perpendicular

• krzych
2012-09-19

I see. I must try to figure out doing it other way. Splitting arc in two pieces is not good solution for me.

• Dongxu Li
2013-02-08

• status: open --> open-accepted