[osg-users] VPB generating terrain for multiple data files

Robert Osfield robert.osfield at gmail.com
Thu Jul 10 07:27:30 PDT 2008


Hi J-S,

A third option might be to modify osgdem so it allows for non zero
default elevation. However, even this is a bit of stop gap.

Ideally should have data throughout your model to define all the
heights you require, if you have holes then all you can come if with
is an acceptable fudge for what this missing data might be.  Perhaps
the easist way to provide this fudge would be to create a single dummy
DEM that covers the entire region and matches the elevations of the
tiles you have.  The actual data would then act is a high res inserts
to this base level DEM.

Robert.

On Thu, Jul 10, 2008 at 1:52 PM, Jean-Sébastien Guay
<jean-sebastien.guay at cm-labs.com> wrote:
> Hello,
>
> I am generating a terrain database using osgdem. I have three source data
> files (GeoTiffs which have correct geospatial information), and I would like
> to generate a single terrain database from all three.
>
> These three files define parts of the ocean floor which are separate, and
> which have some space between them. The heights in these files is around
> -365m. osgdem creates flat (blank) geometry between the tiles, which is what
> I want, but the problem is that it creates this geometry at Z=0. So the
> terrain database looks like:
>
> (data)    (no data)    (data)
>       _______________                Z = 0
>      |               |
>      |               |
> ______|               |_________      Z = -365
>
>
> (viewed from the side)
>
> Are there any ways to fix this? I can think of two off the top of my head:
>
> * Translate all the terrain heights up by about 365 meters, so that
> everything is near Z=0, then generate the terrain, and at run-time translate
> it back down by 365 meters.
> * Use a "fake" tile of data that would encompass the whole terrain and would
> be at about -365 meters everywhere, and then the three data files I have
> would be additional data (higher-res overlays, as I have seen used in some
> terrain database).
>
> Are there any other options? I think the second option is better, but I
> would appreciate others' points of view on this.
>
> Thanks,
>
> J-S
> --
> ______________________________________________________
> Jean-Sebastien Guay    jean-sebastien.guay at cm-labs.com
>                               http://www.cm-labs.com/
>                        http://whitestar02.webhop.org/
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