I'm having some problems connected with the use of textures embedded within IVE
files. The problem arises when I use the same IVE model instance from within
two instances of osgViewer::Viewer which results in unpredictable rendering of
textures in one of the viewer instances, usually the texture goes white when I
delete one viewer instance. If the embedded textures were also compressed, then
I also get some GL errors, typically:
"Warning: detected OpenGL error 'invalid enumerant' at after
RenderBin::draw(..)"
To be honest, I'm not surprised that this sharing of scene graph data between
osg Viewer instances causes a problem. In fact, I’m surprised that more things
don’t break. However, the reason this scenario crops up is that my osg viewer
is running inside a web based plugin, and hence I get an osg viewer instance
within each instance of the plugin that the web browser creates. You might
now be wondering why the browser plugin instances share any scene graph data,
and in fact I was a bit surprised that they were. I didn’t want them to share
data! It turns out that the reason the browser plugin instances share data is
because of the cache provided by the osg Registry singleton. It would have been
nice if each browser plugin instance ended up with their own osg Registry
singleton, but they don’t!
(I don’t really want to get on my hobby horse about all the pains that the
singleton pattern can cause, but this is certainly one to add to my list)
So, my questions boil down to :
If viewer instance 1 caches “cow.ive” in Registry singleton, how do I prevent
viewer instance 2 from using it?
If it does use the cached version, why does cause a problem (seemingly only
with textures that were embedded in IVE)?
Is there a way to “tweak” the IVE embedded textures so they can be shared
successfully in this scenario?
I have reduced the problem down to a simple example (20 lines or so) that
exhibits the same symptoms:
Code:
static osg::ref_ptr<osg::Node> model = NULL;
class ViewerThread : public OpenThreads::Thread
{
public:
ViewerThread(int x, int y) : x(x), y(y) { }
void run()
{
osgViewer::Viewer viewer;
viewer.setUpViewInWindow(x, y, 400, 300);
viewer.setSceneData(model);
viewer.run();
}
int x, y;
};
int main(int argc, char* argv[])
{
model = osgDB::readNodeFile("cow.ive");
ViewerThread* thread1 = new ViewerThread(100, 100);
thread1->start();
ViewerThread* thread2 = new ViewerThread(500, 100);
thread2->start();
while(true);
return 0;
}
Chris Denham
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=44810#44810
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