[osg-users] _intersectionLimit doesn't seem to be working...

Shayne Tueller shayne.tueller at hill.af.mil
Thu Aug 13 12:29:57 PDT 2015


I appreciate the detailed response and correction. My databases are always geocentric round earth built from source DTED or GeoTiff data.

I guess my problems are two-fold which are performance and correlation.  

I was hoping that the general implementation in OSG would get me there on both counts but it is apparent that I will most likely need to roll my own stuff to get the performance and correlation to where I need it to be.

I'm hoping to still use the some of the OSG infrastructure (e.g. the database pager) since I don't want to develop something from scratch entirely.

At this point, correlation seems to be a much larger problem than performance at this point. I was hoping that when I query for terrain height at a given lat,lon, the OSG would page in the highest LOD which would match closely the height of the source data. Unfortunately this is NOT the case. In most instances, I see height deltas of 30-50 feet between what OSG returns and what the actual source data reports for height! I understand the interpolation schemes  between elevation data will introduce differences but I wouldn't expect that much.

Do you know any way to resolve this problem? Is the highest LOD of an osgTerrain::TerrainTile that much different from the source elevation data for its elevation values? It would appear that it is which is a major problem. I suppose I could try and build a height field database from source data in VPB but I haven't been able to get that to work. Further, can a height field be built as a paged LOD database or is it just flat? How's the performance for a height field database? Not too good compared with an osgTerrain database would be my guess...

If you could answer these questions or provide feedback on the correlation issue, that would be great.


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