[osg-users] How to animate the camera in the beginning of the program, then pass it to the controller?

OpenSceneGraph Users osg-users at lists.openscenegraph.org
Mon May 18 17:29:29 PDT 2020

I'm showing a large map over a terrain. In the beginning the user sees the 
whole map from above (call it "position 0"). I want to create an animation 
before that, with the camera approaching the terrain from very far, up to 
the initial position (position 0). Only then the user will be able to 
control the camera with mouse and keyboard. The camera will also slow down 
as it approaches. The whole animation only needs to last 1 or 2 seconds.

I've tried following the first example of chapter 5 from osgCookbook (by 
Rui Wang & Xuelei Qian). My code is:

    osg::Quat quad0;
    controller->setTransformation(osg::Vec3(lonC,latC,800), quad0 ); // 
lonC and latC are central coordinates of the map. This works without the 
    // Animating the camera
    osg::ref_ptr<osgAnimation::FloatLinearChannel> ch = new 
    ch->setName( "euler" );
    ch->setTargetName( "CamAnimCallback" );
    osgAnimation::FloatKeyframeContainer* kfs = 
    kfs->clear(); // why is this needed?
    kfs->push_back( osgAnimation::FloatKeyframe(0.0, 800) ); // from up 
    kfs->push_back( osgAnimation::FloatKeyframe(1.0, 80) ); // down until 
it gets close to the map
    osg::ref_ptr<osgAnimation::Animation> animation = new 
    animation->setPlayMode( osgAnimation::Animation::ONCE );
    animation->addChannel( ch.get() );
    osg::ref_ptr<osgAnimation::UpdateMatrixTransform> updater = new 
    updater->getStackedTransforms().push_back( new 
osgAnimation::StackedTranslateElement("euler", osg::Vec3(lonC,latC,800)) ); 
// initial position
    osg::ref_ptr<osgAnimation::BasicAnimationManager> manager = new 
    manager->registerAnimation( animation.get() );
    osgViewer::ViewerBase::Cameras cameras;
    osg::Camera* camera = cameras[0];
    camera->setUpdateCallback( updater.get() );
    root->setUpdateCallback( manager.get() );

Then I tried to call the animation right before the main loop, and also 
after viewer.frame (running only once, due to "splash", that begins as true)

        if( splash )
            manager->playAnimation( animation.get() );
            splash = false;

However, nothing worked. Any ideas or an example that does something like 


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