[GRASS-user] 3D Buildings

[Thomas Adams]

The following is what Markus wrote on May 18, 2006:


That's pretty easy:

- get 2D building polygons with heights as attribute column (v.in.ogr)
- get DEM (r.in.gdal)
- get orthophoto (r.in.gdal)
- interpolate dem to highres (I used 2m pixels) with r.surf.rst
- extrude 2D buildings to 3D (v.extrude, give building heights attribute
  column as option and 2m DEM as elevation)
- start nviz with 
  nviz dem2m vect=buildings3d col=orthophoto

that's it!



> > If not, is it 
> > possible to use the Trento dataset to create one? One possible use ? if 
> > other details can be worked out ? is to create maps of flood inundation 
> > to show buildings affected by flooding. 
>   

OK, I couldn't resist  :-) 

 http://mpa.itc.it/markus/grass61/demos/rlake/
 -> see at bottom for new screenshot with flooding
    (needs r.lake which is still not in CVS...)


> > I understand one must have the 
> > building data (how was *that* obtained?).
>   

The Trento municipality was going out and digitizing all builings.
Another option is to digitize building footprints from orthophoto
(v.digit) and assign a typical height to each building.

If you are lucky, get 3D DXF buildings and import them with
the recently updated v.in.dxf.


> > This type of presentation is 
> > very effective in capturing the imagination (as it were) of those 
> > possibly affected by flooding.
>   

Fully agreed and done. Except for r.lake everything is in
6.1-CVS.

Only the merge of the flood map with orthophoto could be better
(r.mapcalc will kill the color table, r.patch as well). In February
I did a trick in nviz (see earlier flood screenshots) which I
don't remember today (maybe I loaded the DEM twice or so).


Best,

 Markus


I hope this helps!

Tom


cheg01 at comcast.net wrote:
> I am trying to generate a model very much like the screenshot of Trento on the Grass home page using data for the city of Seattle. I have building outlines and heights in a vector map and accurate elevation data in a raster file. I have used v.extrude to construct the buildings. When I try to plot them in nviz, I get odd disjointed floating surfaces rather than the solid looking 3D objects objects in the Trento example. The extruded vector coverage has only faces, no lines, areas, or centroids. Is that normal? I tried extruding both with and without the "trace" flag set. 
>
> What commands were used to create the beautiful model of Trento? Was it something other than v.extrude and nviz? 
>
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>   


-- 
Thomas E Adams
National Weather Service
Ohio River Forecast Center
1901 South State Route 134
Wilmington, OH 45177

EMAIL:	thomas.adams at noaa.gov

VOICE:	937-383-0528
FAX:	937-383-0033