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osgEphemeris C++ API

An example of building a viewer which include the osgEphemeris::EphemerisModel class is provided in the distribution under src/Viewer. In essence, the osgEphermeris::EphemerisModel is added to the scene graph like any other osg::Node. osgEphemeris::EphemerisModel is the highest level class in the osgEphemeris library and provides the highest level interface for the programmer

The following is main.cpp from the viewer example. 


/* -*-c++-*- OpenSceneGraph - Ephemeris Model Copyright (C) 2006 Don Burns
 *
 * This library is open source and may be redistributed and/or modified under
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * OpenSceneGraph Public License for more details.
*/

#include <osgDB/ReadFile>
#include <osgUtil/Optimizer>
#include <osgProducer/Viewer>

#include <osgEphemeris/EphemerisModel>

int main(int argc, char **argv)
{
    // Parse command line arguments 
    osg::ArgumentParser args( &argc, argv );

    // Set up the viewer
    osgProducer::Viewer viewer(args);
    viewer.setUpViewer(osgProducer::Viewer::STANDARD_SETTINGS);

    // Tell the viewer what to display for a help message
    viewer.getUsage(*args.getApplicationUsage());

    // Load up the models specified on the command line
    osg::ref_ptr<osg::Group> root = new osg::Group;
    osg::ref_ptr<osg::Node> model = osgDB::readNodeFiles(args);
    if( model.valid() )
        root->addChild( model.get() );

    // Define the Ephemeris Model and its radius
    osg::BoundingSphere bs = model->getBound();
    osg::ref_ptr<osgEphemeris::EphemerisModel> ephemerisModel = new osgEphemeris::EphemerisModel;
    ephemerisModel->setSkyDomeRadius( bs.radius()*2 );
    ephemerisModel->setSkyDomeCenter( bs.center() );

    // Optionally, Set the AutoDate and Time to false so we can control it with the GUI
    //ephemerisModel->setAutoDateTime( false );

    // Optionally, uncomment this if you want to move the Skydome, Moon, Planets and StarField with the mouse
    //ephemerisModel->setMoveWithEyePoint(false);

    root->addChild( ephemerisModel.get() );

    osgUtil::Optimizer optimizer;
    optimizer.optimize(root.get());

    // set the scene to render
    viewer.setSceneData(root.get());

    // Realize the viewer
    viewer.realize();
    while( !viewer.done() )
    {
        viewer.sync();
        viewer.update();
        viewer.frame();
    }
    viewer.sync();
    return 0;
}

The following lines set up and add the osgEphemeris::EphemerisModel class: 
    // Define the Ephemeris Model and its radius
    osg::BoundingSphere bs = model->getBound();
    osg::ref_ptr<osgEphemeris::EphemerisModel> ephemerisModel = new osgEphemeris::EphemerisModel;
    ephemerisModel->setSkyDomeRadius( bs.radius()*2 );
    ephemerisModel->setSkyDomeCenter( bs.center() );

    root->addChild( ephemerisModel.get() );

setSkyDomeRadius( bs.radius()*2) and setSkyDomeCenter(bs.center()) is the only real essential call required for practical use of osgEphemeris. All other defaults should result in desired default behavior. Note that we use the bounding sphere of the model loaded on the command line as the parameter for defining the radius of the SkyDome.

Other parameters that can be set at initialization time are AutoDateTime, MoveWithEyepoint, and setting an UpdateCallback. AutoDateTime gets a boolean value and is set with the api thusly,


ephemerisMode->setAutoDateTime( false );

AutoDateTime tells the Ephemeris Model to update the date and time automatically by reading the computer's clock. Thus, the position of the heavenly bodies will reflect the current time as set on the computer. This value is set to true by default. Set this to false if you intend to change the date and time dynamically or by some method other than the current time of the computer's clock.

MoveWithEyePoint gets a boolean value and is set with the API thusly,


ephemerisMode->setMoveWithEyePoint( true );

MoveWithEyePoint tells the Ephemeris Model to keep the skydome and position of the view of the heavenly bodies always centered at the eyepoint. This value is set to true by default. Set this to false if you intend to be able to manipulate the camera to points outside the ephemeris SkyDome. This is useful for debugging or simply getting a sense of the osgEphemeris implementation.

The parameters discussed in this section are settable only at initialization time and remain static for the life of the EphemerisModel class instance. Dynamic changes are discussed in the following sections. Dynamic changes can be set by using a callback method. This UpdateCallack is set statically as well, and is discussed in the next section.

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