[postgis-devel] Dropped DM (Time) dimension with intersections

[Martin Davis]

Not me... the 3D elves must have snuck this one into GEOS   8^)

Obe, Regina wrote:
>
> Chris,
> That was a bit of a trick question :)  It tells me ST_ConvexHull is 
> not ignoring the z-index.
>
>  I was puzzled that convex hull supports 3-d is all since it is a GEOS 
> function and I was under the impression no GEOS functions support 
> 3-d.  But looking at the code, looks like it is one of those ones that 
> somebody snuck in 3d support though I haven't compared with JTS code 
> base to be sure.  Maybe Martin can comment.
>
> Thanks,
> Regina
>
> -----Original Message-----
> From: postgis-devel-bounces at postgis.refractions.net on behalf of Chris 
> Hodgson
> Sent: Tue 10/7/2008 2:10 PM
> To: PostGIS Development Discussion
> Subject: Re: [postgis-devel] Dropped DM (Time) dimension with 
> intersections
>
> I think the answer is, nobody really knows, but it seemed to make as
> much sense as possible given the operation being requested. If it
> doesn't work for your use case then feel free to make a solid argument
> for why we should give a different result and provide a robust method to
> calculate it :-)
>
> Chris
>
>
> Obe, Regina wrote:
> > Which begs the question - what exactly does this tell me?
> > 
> > SELECT
> > ST_AsEWKT(ST_ConvexHull(ST_Collect(ST_GeomFromEWKT('LINESTRING(1 2 3,3
> > 4 5, 3 6 7)'), ST_MakePoint(0, 2, 0))));
> > Result
> > "POLYGON((0 2 0,3 6 7,3 4 5,1 2 3,0 2 0))"
> > 
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-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022