[postgis-tickets] [PostGIS] #2964: ST_OffSetCurve returns EMPTY geometries and other issues

[PostGIS]

#2964: ST_OffSetCurve returns EMPTY geometries and other issues
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  Reporter:  drbullit  |       Owner:  pramsey       
      Type:  defect    |      Status:  closed        
  Priority:  medium    |   Milestone:  PostGIS 2.1.6 
 Component:  postgis   |     Version:  2.1.x         
Resolution:  invalid   |    Keywords:  st_offsetcurve
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Changes (by pramsey):

  * status:  new => closed
  * resolution:  => invalid


Comment:

 The first issue is related directly to the second. An offset curve does
 not just "shift" things (if you want that, maybe look at ST_Affine) it
 produces a line that could be used along with other lines to produce a
 cartographic rendering. For lines that "bend" to the right, the left-hand
 offset will be somewhat longer than the line which will in turn be
 somewhat longer than the right-hand offset.

 Your initial example is offsetting a relatively "short" line by a
 relatively "huge" amount, and since the line is concave in the direction
 you're offsetting it, the offset shrinks away to nothing. Empty. I took
 your example and just started reducing the offset distance until I got an
 answer back. You'll see the picture of it attached.

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/2964#comment:2>
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