#351 Create polyline from existing segments bug

open-accepted
nobody
actions (81)
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
    krzych
    2012-09-17

     
    Attachments
  • krzych
    krzych
    2012-09-17

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

     
  • Rallaz
    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
    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
    Dongxu Li
    2013-02-08

    • status: open --> open-accepted