obj file coordinate is different from what osgearth display

[wu]

obj file coordinate is different from what osgearth display！

i use osgearth  display my pipe (wgs84)

pipe display correct，but  obj Exported is Incorrect。I checked some information but found no reason！

[Boitumelo Ruf]

Have you checked the osgEarth forum: http://forum.osgearth.org/

osgEarth uses an Earth-Centered-Earth-Fixed (ECEF) eucledian coordinate system. Maybe you would need to transform the coordinates inside your .obj file first.

[wu]

my osgearth coordinate system use the wgs84 not ECEF

[Boitumelo Ruf]

Yes, but internally it will transform the wgs84 coordinates to ECEF in order to place them inside the eucledian coordinate system of osg. Look at: http://forum.osgearth.org/LIDAR-data-visualization-td7592224.html

[wu]

Can you provide some ideas? I am a novice for osgearth. I use readNodeFile fnction to read obj  file and display (wgs84), then use writeNodeFile to write obj file then display in cesiumlab.

[Boitumelo Ruf]

So what I have done in reading a point cloud from a .ply file with point coordinate in WGS84 (Lat-Long-Height), is that I iterate over each vertex and convert the coordinates into ECEF format given the functions from osgEarth:

for(uint elementIdx = 0; elementIdx < vertArray->getNumElements(); ++elementIdx)
{
      //--- read current vertex from array

osg::Vec3d llhVert = static_cast<osg::Vec3>((*vertArray)[elementIdx]);

      //--- initialize geopoint
      osgEarth::GeoPoint geoPoint;
      geoPoint = osgEarth::GeoPoint(osgEarth::SpatialReference::get("epsg:4326", "egm96"),
                                    llhVert.x(), llhVert.y(), llhVert.z(),
                                    osgEarth::ALTMODE_ABSOLUTE);

      //--- convert geopoint into ecef point
      osg::Vec3d ecefVert;
      geoPoint.toWorld(ecefVert);

      //--- save vertex
      (*vertArray)[elementIdx] = ecefVert;

}