[GRASS-user] Create 3d models of buildings for use in Google Earth

[Hamish]

Intengu Technologies wrote:
> I have seen the following posts,
> http://grass.itc.it/pipermail/grassuser/2006-May/034214.html and
> http://grass.itc.it/pipermail/grass-dev/2006-June/023820.html
> 
> I have access to orthorectifed high res imagery of towns and would
> like to start creating 3d models of buildings - would actually prefer
> to automate this process as much as possible.
> I do not have access to polygons of buildings with height.

you need to extract building footprints as 2D polygons then assign a
height to each.

idea:
- load imagery into GRASS.
- run a edge detection filter over imagery to automatically make polygons.
   (?? I'm unsure of which module to use, other than custom r.mfilter)
- v.clean to remove small areas (false positives)
- v.digit with ortho image as backdrop for more cleaning (delete non-
   buildings)
- add a "stories" column to 2D polygon vector
- give data or start as all as one column
- v.extrude as in above URL.


> Once models are created they will be viewed on GoogleEarth.

from above URL:
 v.out.ogr format=KML type=face


GRASS 3D vector building NVIZ screenshots:
  http://grass.ibiblio.org/grass61/screenshots/vector.php
  http://bambi.otago.ac.nz/hamish/grass/screenshots/nyc3d_nviz3_midtown.png


Hamish