[GRASS-user] 3D Buildings

[Jachym Cepicky]

Hi,

cheg01 at comcast.net píše v Pá 19. 10. 2007 v 00:43 +0000:
> 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. 

note: NVIZ has problems with concave shapes, like 

+--+  +--+
|  |  |  |
|  +--+  |
+--------+

you can use paraview for 3D data displaying as well

> The extruded vector coverage has only faces, no
>  lines, areas, or centroids. Is that normal? 

faces are to be understood as "3D areas", their centroids are "kernels".
yes, v.extrude generates only faces

> I tried extruding both
>  with and without the "trace" flag set.

this only causes, that the "roofs" of building will "copy" the
elevation. Otherwise, they remain flat.

>  
> 
> What commands were used to create the beautiful model of Trento? Was it something other than v.extrude and nviz? 
> 

Markus knows more ..
but I would say, something like

1 - prepare map with areas (no lines) of building footprints
2 - each area has to have centroid
3 - update building height in the map attribute table
4 - run v.extrude like 

v.extrude in=building_areas out=builidngs3D elevation=your_dem
hcolumn=height_column_in_attribute_table 

hope it helps

Jachym
-- 
Jachym Cepicky
e-mail: jachym.cepicky at gmail.com
URL: http://les-ejk.cz
GPG: http://www.les-ejk.cz/pgp/jachym_cepicky-gpg.pub

-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Toto je =?UTF-8?Q?digit=C3=A1ln=C4=9B?=
	=?ISO-8859-1?Q?_podepsan=E1?= =?UTF-8?Q?_=C4=8D=C3=A1st?=
	=?ISO-8859-1?Q?_zpr=E1vy?=
Url : http://lists.osgeo.org/pipermail/grass-user/attachments/20071019/33216297/attachment.bin