Hi Stefan,
On Mon, 2004-11-15 at 11:16, Stefan Hackl wrote:
> Hi all
>
> In my current OSG-project I have to switch between different scenes. 'Cause
> of
> convenience-reasons I'm still using the SSM at the moment.
>
> To me it seemed logically to use the setRoot()-Method of the
> SimpleSceneManager to switch between the different scenes. A simple example
> to illustrate what I tried:
>
> NodePtr scene = makeTorus(.5, 2, 16, 16);
> NodePtr scene2 = makeTorus(.5, 2, 16, 16);
>
> mgr = new SimpleSceneManager;
> mgr->setWindow(gwin);
> mgr->setRoot(scene);
> mgr->setRoot(scene2);
> mgr->setRoot(scene);
> mgr->showAll();
>
> But this crashes the application, because as it seems the call to
> "mgr->setRoot(scene2);" deletes the old Rootnode (= "scene").
>
> Is this a known/wanted behaviour?
Yes, that's on purpose. The reference counting to clean up trees that
are no longer used will delete the first scene, once you set another
one. If you want to keep it around you will have to explicitly increment
its reference counter (addRefCP()), or use a RefPtr (if you're using a
rather current version of OpenSG).
I'd recommend using a RefPtr for any NodePtrs that you keep in your main
program, as that just automatically solves the problem.
So instead of
NodePtr scene, scene2;
use
#include <OpenSG/OSGRefPtr.h>
RefPtr<NodePtr> scene, scene2;
and it will automatically keep track of the ref count.
Word of warning: as soon as you assign another value to these pointers,
the old one's refcount is decremented, which might delete them. So to
temporarily move around values stored in these, you also have to use
RefPtrs.
Hope it helps
Dirk
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