[postgis-tickets] [PostGIS] #3771: MultiLineStringZ not working when as first argument for ST_Intersection

[PostGIS]

#3771: MultiLineStringZ not working when as first argument for ST_Intersection
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 Reporter:  WaltDixie                            |      Owner:  pramsey
     Type:  defect                               |     Status:  new
 Priority:  medium                               |  Milestone:  Management
                                                 |  2.0
Component:  postgis                              |    Version:  2.2.x
 Keywords:  intersection, multilinestring, 2.5D  |
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 On POSTGIS 2.2, using geos, multilinestringZ aren't handled as expected
 when used as first argument in ST_Intersection.

 Compare sect1bad to sect1best, sect2bad to sect2best in the following
 query:


 {{{
 SELECT li, ST_NumGeometries(geoma),ST_NumGeometries(geomb),
 ST_AsText(ST_Intersection(ST_GeometryN(geoma,li),ST_Force3D(ST_Force2D(geomb))))
 as sect1best,
 ST_AsText(ST_intersection(geoma,ST_Force3D(ST_Force2D(geomb)))) as
 sect1bad,
 ST_AsText(ST_Intersection(ST_Force3D(ST_Force2D(ST_GeometryN(geoma,li))),geomb))
 as sect2best  ,
  ST_AsText(ST_Intersection(ST_Force3D(ST_Force2D(geoma)),geomb)) as
 sect2bad

 FROM
 ( SELECT
 ST_GeomFromText('MULTILINESTRING Z ((0 0 10,0 1 11),(0 1 11, 0 10 20))')
 as geoma,
 ST_GeomFromText('MULTILINESTRING Z ((0 0 5,0 2 9),(0 2 9, 0 3 11))') as
 geomb
 ) data
 CROSS JOIN LATERAL generate_series(1,ST_NumGeometries(geoma)) li(li)
 }}}

 GEOS 3D intersection should lead to the average Z-coordinate at each node
 of the intersection. This is correctly handled in the 'best' cases, where
 the first argument is split into its component LineStringZ segments.
 However, in the 'bad' cases, where the first argument is a
 MultiLineStringZ, the 'inner' node does not have the average Z-coordinate
 but rather retains its original value.
 Clearly this functionality can be avoided by splitting the first argument
 in its component geometries, but somehow this is not handled by default by
 the function.

--
Ticket URL: <https://trac.osgeo.org/postgis/ticket/3771>
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