[postgis-devel] ST_Buffer in 3D supporting Z

[Paragon Corporation]

Sam,
 
Sam,
Not to my knowledge.  There are a couple of hurdles we need to jump before
that step.
 
The big one:
 
GEOS is predominantly 2-D engine:  PostGIS buffer and many other functions
piggy -back on that.
 
so the big question is whether to expand GEOS to handle new 3d types thus
deviating more from its JTS roots or use another engine like Boost or CGAL.
The other option is just to build into PostGIS core, but not sure how much
effort is involved there.
 
Olivier is working on much of the 3D stuff and many of the PostGIS core dev
are having a code sprint in Paris.
 
I think there is still space left if you want to chat up with them and you
can make the trip.
 
http://trac.osgeo.org/postgis/wiki/DevWikiEvent
 
Hope that helps,
Regina
http://www.postgis.us
 
 
 


  _____  

From: postgis-devel-bounces at postgis.refractions.net
[mailto:postgis-devel-bounces at postgis.refractions.net] On Behalf Of Sam
Hariton
Sent: Tuesday, May 01, 2012 4:06 PM
To: postgis-devel at postgis.refractions.net
Subject: [postgis-devel] ST_Buffer in 3D supporting Z


Is anyone looking at adding the ability for st_buffer to keep Z coordinates
as well for 3-dimensional spaces?  If so, I'd like to help.

The Postgis 2.0 docs state:  This function ignores the third dimension (z)
and will always give a 2-d buffer even when presented with a 3d-geometry.

Right now 




select st_astext(st_buffer(geomfromEWKT('POINT(0 0 0)'),1));


Generates a flat Polygon/Circle of radius 1 (completely dropping the z
dimension):

 POLYGON((1 0,0.980785280403231 -0.195090322016128,0.923879532511287
-0.382683432365089,0.831469612302546 -0.555570233019602,0.707106781186548
-0.707106781186547,0.555570233019603 -0.831469612302545,0.382683432365091
-0.923879532511286,0.19509032201613 -0.98078528040323,1.61554255216634e-15
-1,-0.195090322016126 -0.980785280403231,-0.382683432365088
-0.923879532511288,-0.555570233019601 -0.831469612302546,-0.707106781186546
-0.707106781186549,-0.831469612302544 -0.555570233019604,-0.923879532511286
-0.382683432365092,-0.98078528040323 -0.195090322016131,-1
-3.23108510433268e-15,-0.980785280403231
0.195090322016125,-0.923879532511288
 0.382683432365086,-0.831469612302547 0.555570233019599,-0.70710678118655
0.707106781186545,-0.555570233019606 0.831469612302543,-0.382683432365094
0.923879532511285,-0.195090322016132 0.98078528040323,-3.73640463187386e-15
1,0.195090322016125 0.980785280403231,0.382683432365087
0.923879532511288,0.5555702330196 0.831469612302547,0.707106781186545
0.70710678118655,0.831469612302544 0.555570233019604,0.923879532511286
0.382683432365092,0.98078528040323 0.19509032201613,1 0))

Whereas, if it had z support it should actually generate a Polyhedral
Surface/Sphere of radius 1 centered on (0 0 0)


 - Sam


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