[postgis-devel] [PostGIS] #973: ST_GetFaceGeometry - don't intercept the UniverseFace

PostGIS trac at osgeo.org
Tue May 24 06:45:20 PDT 2011

#973: ST_GetFaceGeometry - don't intercept the UniverseFace
 Reporter:  aperi2007  |       Owner:  strk         
     Type:  defect     |      Status:  assigned     
 Priority:  medium     |   Milestone:  PostGIS 2.0.0
Component:  topology   |     Version:  trunk        
 Keywords:             |  

Comment(by aperi2007):

 Replying to [comment:7 strk]:
 > Great, in this case I'll proceed in that direction.
 > Does it say anything similar for ST_GetFaceEdges ?

 the ISO specs don't want to exception for ST_GetFaceEdge when calling with

 The explanation is in the ISO specs:

 They say:

 >ST_GetFaceEdges: for the provided topology-name and face ID, returns a
 table containing the
 >integer edge IDs for the edges which bound the face, in counterclockwise
 order. Edge IDs will be
 >negated in the query result if the face is right of the edge when looking
 in the direction of the edge
 >from start to end node.

 ST_GetFaceEdge formerly don't return the geometry but instead it return
 the Edges delimiting the Face.
 Even the UniverseFace has some edges to delimiting it.
 They are simply the edges that has the LEFT_FACE = 0 OR RIGHT_FACE = 0.

 So the

 select ST_GetFaceEdges('toponame', 0)

 will return the result of
 something like

 select edge_id from 'toponame'.edge_data where ( (LEFT_FACE=0) OR

 I guess a bit more complex because it should be in counterclockwise

Ticket URL: <http://trac.osgeo.org/postgis/ticket/973#comment:8>
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