[GRASS-user] NVIZ - problem display 3D polygon (v.extrude polygons)

[Markus Neteler]

On Sat, Aug 6, 2011 at 9:24 PM, DelphineJB <del_cadarn at hotmail.com> wrote:
> Bonjour,
>
> I do apologise for this problem it must have been posted before but I
> couldn't get an answer in the archive.
>
> I am having problems to see vectors I have added height to with v.extrude .
> The trick is that I am actually using the e.g. given in NETELER, M and H.
> MITASOVA /Open Source GIS a GRASS GIS Approach/ with the North Carolina
> sample data. So in theory, this example should really be working...
>
> Here is what I did
>
> g.region rast=el_D792_6m -p
>
> v.extract P079215 out=bldg_resid_a where="layer='BLDG_RESID_BL'"
> v.extract P079215 out=bldg_cmcl_a where="layer='BLDG_COMMER_BL'"

There was an omission in that part of the book:

http://www.grassbook.org/errata_menu3rd.php

You need to convert the vector types first.

> v.extrude -t bldg_resid_a out=bldg_resid_a_3d height=10 elev=el_D792_6m
> v.extrude -t bldg_cmcl_a out=bldg_cmcl_a_3d height=15 elev=el_D792_6m
>
> g.region rural_1m -p
> nviz elev_lid792_1m col=ortho_2001_t792_1m
> vect=bldg_resid_a_3d,bldg_cmcl_a_3d
>
> I am using Grass 6.4.1 with the python GUI on Windows 7
>
> Now the infamous result is just some line on what should be the height of
> the building, like if NVIZ read it as lines rather than 3D surface...

With the correction, it will work.

Markus