[postgis-tickets] [PostGIS] #3046: topology.GetRingEdges return wrong ring when edge.next_left/right = edge

[PostGIS]

#3046: topology.GetRingEdges return wrong ring when edge.next_left/right = edge
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  Reporter:  remic     |       Owner:  strk  
      Type:  defect    |      Status:  closed
  Priority:  medium    |   Milestone:        
 Component:  topology  |     Version:  2.1.x 
Resolution:  invalid   |    Keywords:        
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Comment(by remic):

 Again I strongly disagree.
 Of course you walk on the edge side, this is precisely why walking from
 -N or +N shouldn't give the same result (the sign change the direction of
 edge).
 So even when walking always to the left, you should have different
 results.

 In fact, our data structure is a disguised half-edge.

 When you have the correct ring, it is easy to find which edges are
 "isolated" (that is next_left_edge or next_right_edge = edge_id), it is
 simply the edge that are present with both sign in the ring.

 CHeers,
 Rémi-C

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/3046#comment:5>
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