[postgis-tickets] [PostGIS] #3835: ST_StraightSkeleton returns degenerate line segments

[PostGIS]

#3835: ST_StraightSkeleton returns degenerate line segments
----------------------+----------------------------
  Reporter:  wrog     |      Owner:  robe
      Type:  defect   |     Status:  new
  Priority:  medium   |  Milestone:  PostGIS SFCGAL
 Component:  postgis  |    Version:  2.3.x
Resolution:           |   Keywords:
----------------------+----------------------------
Changes (by robe):

 * milestone:  PostGIS 2.3.4 => PostGIS SFCGAL


Comment:

 Okay still seems to be an issue with head.

 Testing with:


 {{{
 POSTGIS="2.4.0dev r15671" PGSQL="100" GEOS="3.7.0dev-CAPI-1.11.0 8fe2ce6"
 SFCGAL="1.3.1" PROJ="Rel. 4.9.1, 04 March 2015" GDAL="GDAL 2.2.1, released
 2017/06/23" LIBXML="2.7.8" LIBJSON="0.12" LIBPROTOBUF="1.2.1" RASTER
 }}}


 {{{

 WITH bt(box) AS (
   SELECT st_makebox2d(st_point(1296000,202400),st_point(1297000,212400))
 )
 SELECT d.path[1], St_astext(d.geom) , ST_Length(d.geom)
 FROM bt, st_dump(
   st_straightskeleton(st_difference(st_buffer(box,2000,2),box))
 ) as d
 WHERE st_startpoint(d.geom) = st_endpoint(d.geom);
 }}}

 I get output:


 {{{
  path |                                   st_astext
 | st_length
 ------+-------------------------------------------------------------------------------+-----------
    17 | LINESTRING(1295198.91236738 201598.91236738,1295198.91236738
 201598.91236738) |         0
    20 | LINESTRING(1295198.91236738 213201.08763262,1295198.91236738
 213201.08763262) |         0
    22 | LINESTRING(1297801.08763262 201598.91236738,1297801.08763262
 201598.91236738) |         0
    23 | LINESTRING(1297801.08763262 213201.08763262,1297801.08763262
 213201.08763262) |         0
 (4 rows)

 }}}


 I've ticketed the issue upstream at
 https://github.com/Oslandia/SFCGAL/issues/143

 and will flag this as a SFCGAL since I don't think it needs fixing in
 PostGIS

--
Ticket URL: <https://trac.osgeo.org/postgis/ticket/3835#comment:2>
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