[Qgis-developer] 3D Points

Matthew Denno mgdenno at gmail.com
Sun Dec 27 21:15:00 EST 2009

Hi Marco,

Thanks for your input.  I took a look at your code in
qgstininterpolator.cpp.  That looks like a pretty good way to do it,
but is not exactly what I was hoping for.  It would be nice if we
could access the z-coordinate with QgsPoint.  I know there has been
some discussion of this on the list in the past; maybe I will have to
look into this more.  Maybe I will switch over to using a code similar
to yours instead of using OGR which does have access to the
z-coordinate but is not part of the QGIS API.  In fact, the code I am
working on is very similar to yours; it adds points/lines to a
Delaunay triangulation (CGAL library) which supports exact arithmetic.
 Anyway, thanks again.


On Sun, Dec 27, 2009 at 7:33 AM, Marco Hugentobler <marco at hugis.net> wrote:
> Hi Matthew
> There is already support for 3D points. I'm using it e.g. in the interpolation
> plugin / analysis library to do interpolation from 2.5D shapefiles. I haven't
> tried it with postgis, but suppose that it works too.
> But afaik, you cannot access the z-coordinate with QgsPoint. You need to check
> if the geometry is a 2.5D type and parse the WKB to get it (see e.g.
> qgstininterpolator.cpp:204)
> Point3D is a point type in the interpolation code. But it comes originally
> from external code, so cannot be used together with the core classes.
> Regards,
> Marco
> Am Samstag, 26. Dezember 2009 15.36:03 schrieb Matthew Denno:
>> Just a quick question because I am curious.  Is the next version (1.4)
>>  going to have support for 3D points?  I see a Point3D class in the
>>  documentation. Right now my app uses OGR dirctly for this but I didn't
>>  want to do it that way.  Also, what is the difference between a Point25D
>>  and Point3D?
>> Matt
> --
> Dr. Marco Hugentobler
> HUGIS - GIS programming and consulting
> Webereistr. 66
> CH-8134 Zürich
> marco at hugis.net
> http://homepage.hispeed.ch/hugis/
> Technical Advisor QGIS Project Steering Committee

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