Hello Bart,
I must be missing something obvious I guess, but for me it isn't obvious (yet).
Not quite obvious, I would say, but something you could have found out
by using the debugger or looking at the OSG code for the functions
you're calling. Both are tools you should learn to use when you develop
with third-party libraries, especially open source ones like OSG.
You don't need to create a new camera. In fact, in creating a new camera
and replacing the view's camera with yours AFTER the
view->setUpViewOnSingleScreen(x) line, you're effectively destroying the
graphics context that the setUpView...() function created for you. And
your own camera has no graphics context, so you see a black screen.
When you create an osgViewer::View, it creates an osg::Camera for you,
with appropriate settings. When you call view->setUpView...(), it
creates a graphics context and sets it on the view's camera. Creating
your own camera and setting it on the view basically voids all that work
that was done for you.
So just remove the lines:
osg::Camera* camera = new osg::Camera;
...
view->setCamera(camera);
for both your views, and whenever you used the camera variable, use
view->getCamera() instead.
I'm not sure why you say that just setting a manipulator on the view did
not give a black screen. Running your code with the
setCameraManipulator(Tman) line uncommented, I still get a black screen
in the second view, as I would expect. The camera manipulator is not
related to the graphics context in any way, it only acts on the camera's
view matrix. If the camera doesn't have a graphics context, you'll get a
black screen whether you have a camera manipulator or not.
What will make a difference is using viewer.run() instead of while
!viewer.done()) viewer.frame(); . The former is a shortcut for doing
quick demos. It will do a few things for you, including setting a camera
manipulator and creating a graphics context that spans all your screens.
So this might have led you to believe that the two were related, but
they're not. It's just that viewer.run() does these two things for
you... But if you don't want to use a camera manipulator, you don't want
viewer.run() anyways.
This kind of thing could be seen in a debugger by the way. By setting a
breakpoint when you create your views, you could have seen that the view
already had a camera as soon as it was created, then that the
setUpView...() function had set a graphics context on that camera, and
then when you assigned your own camera you could have seen that it had
no graphics context.
Finally, for future reference, if you want someone to actually compile
and run your code, it's much more helpful to include a complete file,
with all necessary headers etc that you know compiles, rather than copy
and paste some code (even if it's almost complete). It just provides a
lower barrier for people to help you easily... For example, here's a
source file ready to be compiled that shows what I'm talking about
above. You should see the cow on both screens. (note I've commented out
checking the arguments for -2, so I can test without any command line
arguments, again make it easy for people to help you...)
Hope this helps,
J-S
--
______________________________________________________
Jean-Sebastien Guay jean-sebastien.g...@cm-labs.com
http://www.cm-labs.com/
http://whitestar02.webhop.org/
#include <osgDB/ReadFile>
#include <osg/Group>
#include <osgViewer/CompositeViewer>
#include <osgViewer/View>
#include <osgGA/TrackballManipulator>
int main(int argc, char** argv)
{
osg::ArgumentParser arguments(&argc, argv);
osg::Group* scene = new osg::Group();
osg::Node* groundNode = NULL;
osg::Node* tankNode = NULL;
groundNode = osgDB::readNodeFile("cow.osg");
scene->addChild(groundNode);
osgGA::TrackballManipulator* Tman = new osgGA::TrackballManipulator;
// construct the viewer.
osgViewer::CompositeViewer viewer(arguments);
//if (arguments.read("-2"))
{
// view one
{
//osg::Camera* camera = new osg::Camera; //
don't create a new camera
osgViewer::View* view = new osgViewer::View;
osg::Camera* camera = view->getCamera(); // use the
view's existing camera instead.
view->setName("View one");
viewer.addView(view);
view->setUpViewOnSingleScreen(0);
view->setSceneData(scene);
// Get the scene bounding sphere
osg::BoundingSphere bsph = scene->getBound();
// Look at the center of the scene
osg::Vec3 lookAt = bsph.center();
// Place eye at an appropriate distance 'south' of the look-at point
osg::Vec3 eyef = lookAt + osg::Vec3(0,-1,0) * bsph.radius() * 3.5f;
// Set camera view matrix
camera->setViewMatrixAsLookAt(eyef, lookAt, osg::Vec3(0,0,1));
//view->setCamera(camera);
}
// view two
{
//osg::Camera* camera = new osg::Camera; //
don't create a new camera
osgViewer::View* view = new osgViewer::View;
osg::Camera* camera = view->getCamera(); // use the
view's existing camera instead.
view->setName("View two");
viewer.addView(view);
view->setUpViewOnSingleScreen(1);
view->setSceneData(scene);
// Get the scene bounding sphere
osg::BoundingSphere bsph = scene->getBound();
// Look at the center of the scene
osg::Vec3 lookAt = bsph.center();
// Place eye at an appropriate distance 'south' of the look-at point
osg::Vec3 eyef = lookAt + osg::Vec3(0,-1,0) * bsph.radius() * 1.5f;
// Set camera view matrix
camera->setViewMatrixAsLookAt(eyef, lookAt, osg::Vec3(0,0,1));
//view->setCamera(camera);
//view->setCameraManipulator(Tman);
}
}
viewer.realize();
while(!viewer.done())
{
viewer.frame();
}
}
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