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

Jean-Sébastien Guay jean-sebastien.guay at cm-labs.com
Thu Jul 10 05:52:15 PDT 2008


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.


Jean-Sebastien Guay    jean-sebastien.guay at cm-labs.com

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