[postgis-users] Experience with GDL objects

[Paul Ramsey]

Hi Ricardo,

   The GIS and CAD worlds remain oddly separate. The only "true 3D" 
applications I have seen of GIS is in the geological field, where 
modelling underground structures is done with full 3D objects. 
Interestingly, the people doing that have to often use CAD tools for 
their work. Meanwhile, the CAD people do not seem to care much about 
where thier objects are on the ground. It is enough that they be 
described in a detailed way relative to a reference point. So CAD people 
live in a cartesian world while GIS people live in a spherical (oblate 
spheroid) world.

   I wonder whether an integrated approach is really required for most 
applications.  For many apps, using GIS tools to navigate to an object 
of interest, then getting a CAD view of the particular object, seems 
like a straight forward amalgam.

   I haven't seen any CAD / PostGIS tie-ins in the 3D space. I am not 
sure what the best data model would be, frankly. Like many map layers, 
detailed 3D objects would be very scale dependant. Effective 
presentation of the data at multiple scales would require simplification 
of the features, and proxying with other features.

   The vterrain.org site has some integrated terrain + buildings going 
on. I think that vterrain might be the best long term open source front 
end to the problem. But I am not sure precisely what the problem is. :) 
If it is the creation of a seamless multi-scale model of the world, then 
that is the long term vterrain goal.

Paul

Mireles Ricardo wrote:
> I am seeking to understand the relationship between GIS technologies
> (namely PostGIS) and GDL objects.
> 
> Recently I saw a presentation of web-delivered 3D modeling of
> buildings using GDL objects.
> 
> GDL stands for Geometric Description Language, and comes out of the
> GraphiSoft ArchiCAD world (see
> http://www.gdlalliance.com/Parametric/GDL.html ).
> 
> With the right set-up (browser, plug-ins, etc.) a web-page with GDL
> objects looks alot like TerrainServer, or ArcView 3D Analyst.
> 
> Here is some static examples (screenshots): 
> http://onuma.com/VRIS/Objects/Schools.html
> 
> It seems like GDL, is an "open" standard, but I'm not sure.
> 
> What other technologies/stratregies are similar? Has anyone here seen
> GDL tied into GIS/PostGIS somewhere?


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      | Paul Ramsey
      | Refractions Research
      | Email: pramsey at refractions.net
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