Hi Chuck, osgSim:HeightAboveTerrain or osgSim:ElevationSlice might be of interest, the later is the one I'd use as it give you the whole data. But... both of these query for the heights res tiles, which won't be aligned to the terrain at all LOD levels soo... it won't actually work that well for a general runtime database.
As for the specifics of what its not working with a TXP database I can't say - the osgSim classes as explicitly designed to handle paged database so in theory should work just fine. Perhaps the fact that the TXP plugin does some funky management of PagedLOD levels to try and restrict how far apart adjacent tiles can be in LOD level is the cause. One would need to go through with a debugger to be sure. Either way if you want a visual grid on your paged terrain I don't think computing intersections and generating polygons will cut it due to the nature of elevation changes as LOD levels pop in. The best approach you could try would be to compute the intersections on the fly as tiles a loaded in via a custom Registry::ReadCallback - this would use the PlaneIntersector to get the intersections with each new loaded subgraph. However, the approach I'd use would be a custom shader that computes the position in space of each fragment on the terrain and decides to render different colours depending in the fragment was closest enough to a grid interval or not. Such a shader would work with any type of terrain and would be pretty light weight. Robert. On Thu, Mar 6, 2008 at 5:50 PM, Cole, Charles E. (LARC-B702)[GENEX SYSTEMS] <[EMAIL PROTECTED]> wrote: > I'm trying to use the osgSim::HeightAboveTerrain class to compute > terrain heights at various points within a TXP database. The intent is > to get an array of Vec3d's such that I can create a grid pattern using > osg::Geometry that (coarsely) represents the database (I tried the > OverlayNode and other examples, but the textures just didn't work for > me). > > In my code, I basically create a osgSim::HeightAboveTerrain object, then > loop through various points laterally offset from the terrain's center > point (as determined by the bounding sphere). With each point, I call > the 'computeHeightAboveTerrain' method using the terrain node (read in > using osgDB::readNodeFile) and the computed point to get the height > above the terrain. Unfortunately, all of the calls return the same > height. The terrain is of a mountainous region, so the actual terrain > height varies considerably from point to point. > > As a check, I ran the osgintersection example using the TXP database. > For this example, it also returns a constant height (and the same height > that I receive in my code). > > Any suggestions on why a constant height is returned? Are there steps > that I'm missing? I searched the mailing list archives and couldn't > find any discussions related to my problem. BTW, The TXP database is a > paged LOD database with a Z-up orientation. > > TIA. > > chuck > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
