Hi,
Let me preface this by saying that I know how to make my code do what I want it
to, so this question is of low importance and arises from doing something that
could(should?) be considered silly- dynamic allocation within a callback
operator method when the callback can have a class member instead. However,
I'm still curious about the behavior, and/or if others see this in a different
way than I do.
What I'm seeing (code below produces this on my two setups): The second sphere
(which should always be green) flickers red. Uncommenting the traverse line in
the operator method makes the flickering noticably worse. The flicker color
being red is not a coincidence, it flickers whatever color the first sphere is.
Making 'mat' a class member of the derived callback instead of creating a 'new'
version of it eliminates this problem. As I said, this fixes my problem... but
even if dynamically allocating a new Material each time is inefficient, I was
still surprised at the flickering behavior. In my quest to learn more about
all of this, I thought I'd see if anyone could enlighten me as to what's going
on.
Two questions:
1) Why is one sphere flickering when a new Material (ref_ptr or plain non-smart
pointer) is created in the callback?
2) Why does calling traverse within the operator method (as the Quick Start
Guide indicates) make the flickering worse?
I'm using XP/VisStudio2008Express on one machine, and Windows7/VisStudio9 on
another, osg 2.8.2 on both, just in case it matters.
Thoughts?
Code:
class MyCallback : public osg::NodeCallback
{
public:
MyCallback(osg::Vec4 c){color=c;}
virtual void operator()(osg::Node* n, osg::NodeVisitor* nv)
{
osg::ref_ptr<osg::MatrixTransform> mt = dynamic_cast<osg::MatrixTransform*>(n);
osg::ref_ptr<osg::Material> mat = new osg::Material();
mat->setDiffuse(osg::Material::FRONT, color);
mt->getOrCreateStateSet()->setAttribute(mat);
//traverse(n, nv);
}
protected:
osg::Vec4 color;
};
int _tmain(int argc, char * argv[])
{
osg::ref_ptr<osg::Group> root = new osg::Group();
osg::ref_ptr<osg::Geode> sphere = new osg::Geode();
sphere->addDrawable(new osg::ShapeDrawable(new osg::Sphere(osg::Vec3(0., 0.,
0.), 0.1)));
osg::Vec4 color1, color2;
color1.set(1., 0., 0., 0.);
color2.set(0., 1., 0., 0.);
{
osg::ref_ptr<osg::MatrixTransform> mt = new osg::MatrixTransform();
root->addChild(mt);
mt->addChild(sphere);
mt->setMatrix(osg::Matrix::translate(-.1, 0., 0.));
mt->setUpdateCallback(new MyCallback(color1));
}
{
osg::ref_ptr<osg::MatrixTransform> mt = new osg::MatrixTransform();
root->addChild(mt);
mt->addChild(sphere);
mt->setMatrix(osg::Matrix::translate(0.1, 0., 0.));
mt->setUpdateCallback(new MyCallback(color2));
}
osgViewer::Viewer v;
v.setSceneData(root);
v.getCamera()->setViewMatrixAsLookAt(osg::Vec3(0., -.500, 0.), osg::Vec3(0.,
0., 0.), osg::Vec3(0., 0., 1.));
v.setUpViewInWindow(750, 550, 600, 400, 0);
while(!v.done())
{
v.frame();
}
return 0;
}
Cheers,
Tom
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=30012#30012
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