Thanks Robert. I was hoping what seemed to be the simplest solution would work. I'll pursue a little further, particularly in the TXP plug-in. Is there a way to force specific LOD's to load (particularly the highest)?
I think the shader solution is probably the best and would actually lead into some other work that I'd like to do. Unfortunately, I really don't know anything about shaders. So, I've got quite a bit of learning to do before I can attempt. chuck > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:osg-users- > [EMAIL PROTECTED] On Behalf Of Robert Osfield > Sent: Thursday, March 06, 2008 1:04 PM > To: OpenSceneGraph Users > Subject: Re: [osg-users] osgSim::HeightAboveTerrain and osgintersection > > 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.or g _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
