Chris 'Xenon' Hanson wrote:
> On 9/14/2011 7:55 AM, Ethan Fahy wrote:
>
> > To answer my own question, yes, the code snippet that I posted does work
> > and allows me to attach an object to the terrain using lat lon elevation.
> > The next step is to be able to place an object on the terrain by only
> > giving it a lat lot and having it figure out the elevation automatically...
> >
>
> http://eckhart.stderr.org/doc/openscenegraph-doc/openscenegraph/classosgSim_1_1HeightAboveTerrain.html
>
> Use that to query the terrain elevation at a given location.
>
Thanks! Just to document my method for anyone else that stumbles upon this:
I read in a terrain.ive file that was converted using osgdem with the
--geocentric flag (mandatory step). In order to gain access to the ellipsoid
model in the terrain.ive file, I did this:
Code:
osg::CoordinateSystemNode* terrainTemp =
dynamic_cast<osg::CoordinateSystemNode*> (terrain);
osg::ref_ptr<osg::EllipsoidModel> ellipsoid =
terrainTemp->getEllipsoidModel();
Then I wrote this function that accepts a lat lon in degrees plus the terrain:
Code:
double GetHeightOnTerrain(double lat, double lon, osg::CoordinateSystemNode*
terrain)
{
double X,Y,Z;
double maxElevation = 100000.0;//arbitrarily large number way above terrain
[meters]
terrain->getEllipsoidModel()->convertLatLongHeightToXYZ(osg::DegreesToRadians(lat),
osg::DegreesToRadians(lon),
maxElevation, X,Y,Z);
double hat =
osgSim::HeightAboveTerrain::computeHeightAboveTerrain(terrain,osg::Vec3(X,Y,Z),
-1);
return (maxElevation - hat);
}
When I want to get a terrain height from a lat lon, I do this:
Code:
//Find Terrain Elevation Based on Lat Lon
float treeLat = 50.0;
float treeLon = 50.0;
// Place Tree on Ellipsoid Model Based on Lat Lon
double treeAltitude = GetHeightOnTerrain(treeLat, treeLon, terrainTemp);
osg::ref_ptr<osg::MatrixTransform> treePlacer = new
osg::MatrixTransform();
osg::Matrixd treePosition;
ellipsoid->computeLocalToWorldTransformFromLatLongHeight(osg::DegreesToRadians(treeLat),osg::DegreesToRadians(treeLon),
treeAltitude, treePosition);
treePlacer->setMatrix(treePosition);
The treePlacer can be attached to the root alongside the terrain itself, then
the tree object can be attached to the treePotision as a child in order to
position the tree on the terrain.
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=42797#42797
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