Hi Jeffrey, In the 2.x series of the OSG there is an osgfadetext example that uses a ClusterCullingCallback to cull the text when its on the far side of the earth, and disables depth test when its on the front side - this sounds similar to your needs.
Robert. On 10/16/07, Jeffrey M Short <[EMAIL PROTECTED]> wrote: > > Hi, > > First off I'm using OSG 1.0. > > I am creating an application that has globe viewing features. The user can > add an location object at a given Latitude, Longitude and Altitude. Then a > 3d model and a text label is placed at that location. Both the model node > and the text geode are placed under a MatrixTransform with the matrix set > using the > osg::EllipsoidModel->computeLocalToWorldTransformFromLatLongHeight. The > text uses SCREEN_COORDS as the CharacterSizeMode and uses SCREEN as the > AxisAlignment. > > The problem is that the text is intersects the earth when viewed from > certain viewpoints. I would like to draw the earth first, then draw all > the text, but only draw any particular text geode if and only if the > location is not clipped by the Earth. > > > My first attempt was as follow: > I set the text geode depth test to osg::Depth::ALWAYS. > > I added a custom osg::Drawable::CullCallback to the text geodes. In > the callback's virtual bool cull(osg::NodeVisitor* nv, osg::Drawable* > drawable, osg::State*) const function I got the eye location and the text > location in Earth Centered Cartesian Coordinates. Then if the dot product > of these 2 position vectors is < 0, return true so the text is culled. > > > One problem I encountered here was getting the eye location from > CullVisitor::getEyePoint(). This function seems to return the EyePoint in > local coordinates. I tried using the > osg::computeLocalToWorld(nv->getNodePath()) matrix to transform the > EyePoint to Earth Centered coordinates but that didn't work. I had > transform osg::Vec4(EyePoint, 1) by the inverse of > osg::EllipoidModel::computeLocalToWorldTransformFromXYZ to get the job > done. > > This method works but only when the camera is targeted at the center of the > earth and it only works for locations with 0 altitude (imagine a location > on the "other side" of the Earth from where you are viewing. If the > location has a large enough altitude you could still see it). > > Any suggestions on a better way to accomplish this? > > Thanks > Jeff > > > > Computer Sciences Corporation > Registered Office: 2100 East Grand Avenue, El Segundo California 90245, USA > Registered in USA No: C-489-59 > > ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- > > This is a PRIVATE message. If you are not the intended recipient, please > delete without copying and kindly advise us by e-mail of the mistake in > delivery. > NOTE: Regardless of content, this e-mail shall not operate to bind CSC to > any order or other contract unless pursuant to explicit written agreement > or government initiative expressly permitting the use of e-mail for such > purpose. > ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- > > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
