[osg-users] Setting camera Viewmatrix with TrackBallManipulator Matrix gives nothing but black screen

[Bart Jan Schuit]

Hi,

I'm trying to setup some cameras without a manipulator. When I assign a Trackballmanipulator on the vies, I get the cow projected on the screen. But as soon as I manually setup the cameras, I get a completely black screen.
I extract eye, center and up from Tman (Trackballmanipulator) by Tman->getMatrix().lookat(eye, center, up).

This gives some nice coordinates, but when I put these in a camera without a manipulator like Tman, I just get a black screen. What am I doing wrong here?

Code:

int main( int argc, char **argv )
{

// use an ArgumentParser object to manage the program arguments.
osg::ArgumentParser arguments(&argc,argv);

osg::Group* scene = new osg::Group();
osg::Node* groundNode = NULL;
groundNode = osgDB::readNodeFile("cow.osg");

scene->addChild(groundNode);

osgViewer::CompositeViewer viewer(arguments);

if (arguments.read("-2"))
{

// view one
{

osg::Vec3d eye = osg::Vec3d(0,0,250);
osg::Vec3d center = osg::Vec3d(0,0,250);
osg::Vec3d up = osg::Vec3d(0,0,-1);
osg::Quat rotation;
osg::Matrixd viewmat;

osg::Camera* camera = new osg::Camera;
osgViewer::View* view = new osgViewer::View;
view->setName("View one");
viewer.addView(view);
//camera->setProjectionMatrix( osg::Matrix::ortho2D(0,512,0,512) ); //not doing anything
//camera->setReferenceFrame( osg::Transform::ABSOLUTE_RF );
//camera->setViewMatrix( osg::Matrix::identity() );
view->setCameraManipulator(Tman);
//Tman->setAutoComputeHomePosition(false);
view->setUpViewOnSingleScreen(0);
view->setSceneData(scene);
//view->setCamera(camera);

}

// view two
{
osg::Matrixd viewmat;
osg::Camera* camera = new osg::Camera;
osgViewer::View* view = new osgViewer::View;
view->setName("View two");
viewer.addView(view);
view->setUpViewOnSingleScreen(1);
view->setSceneData(scene);
//view->setCamera(camera);
view->setCameraManipulator(Tman);
view->setName("right");
osg::Vec3d eye = osg::Vec3d(0,0,25);
osg::Vec3d center = osg::Vec3d(0,0,25);
osg::Vec3d up = osg::Vec3d(0,0,-1);
}
}
viewer.realize();

while(!viewer.done())
{

osg::Vec3d eye = osg::Vec3d(0,0,50);
osg::Vec3d center = osg::Vec3d(0,0,50);
osg::Vec3d up = osg::Vec3d(0,0,-1);
Tman->setHomePosition(eye,center,up); //not working. Doesn't matter how I set eye, center etc.
viewer.frame();
}
}

------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=34890#34890

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[Trajce (Nick) Nikolov]

if this is your code (with all the comments) then here is what you should do:

- forget about your osg::Camera* camera = new Camera; // there is already a Camera attached to the View

- use view.getCamera()->setProjectionMatrixAsPerspective(45,1,1,1000);

- no need to attach any CameraManipulator if you want to set the view matrix by your own (although that is the purpose of the CameraManipulator, to change the view matrix - probably you do it this way when you get more familiar with the code)

- in your loop you do viewer.getView(0)->getCamera()->setViewMatrixAsLookAt(eye,center,up)

-Nick