Hi Jeremy,
In your case where you have data being shared between a subclass and
its base class I feel that this duplication of ref_ptr<> to the shared
data is inappropriate. Rather what you should use in your own code is
dynamic_cast<Vec3Array*> where you need access to the array, or to
provide a convenience method to getVec3Array() { return
dynamic_cast<Vec3Array*>(getVertexArray()); }
Would this solve this problem?
Robert.
On Feb 18, 2008 7:31 PM, Jeremy Moles <[EMAIL PROTECTED]> wrote:
> Thanks for the response, Robert.
>
> On Mon, 2008-02-18 at 17:54 +0000, Robert Osfield wrote:
> > Hi Jeremy,
> >
> > Most OSG objects implement the clone operator with CopyOp parameter so
> > you can just pass this along. For objects like std::vector etc you
> > would typically just implement a deep copy, i.e. copy all the
> > contents, unless of course its a vector of ref_ptr<>'s in which case
> > copying the contents of the vector shares the pointers so you have to
> > do a element by element deep copy op on the objects if that's what is
> > required.
> >
> > To see examples of various ways of implementing the copy operator have
> > a look at the implementations - they are all over the OSG.
>
> Hmm, I think I probably wasn't as clear as I could have been--or perhaps
> I'm still misunderstanding. Let me provide another very simple,
> contrived example here:
>
>
>
> // -----------------------------------------------------------
>
> struct MyGeometry: public Geometry {
> ref_ptr<Vec3Array> _verts;
>
> MyGeometry() {
> _verts = allocateSomeGeometry();
>
> setVertexArray(_verts.get());
> }
>
> MyGeometry(const MyGeometry& myG, const CopyOp& co):
> Geometry(myG, co) {
> }
> }
>
> MyGeometry* mg1 = new MyGeometry();
> MyGeometry* mg2 = mg1->clone(CopyOp::DEEP_COPY_ALL);
>
> // -----------------------------------------------------------
>
>
>
> With the above code, the _verts ref_ptr in mg2 won't point to anything,
> since I haven't intialized it, although mg2 WILL have the proper
> geometry, since there was a deep copy of all the existing data (in fact,
> osgWidget introduces it's own "cloneAs" method which always does a
> DEEP_COPY, since this is almost always desired). What I'm wanting to
> do--and haven't been able to find an example of in OSG yet--is an easy
> way to set _verts in the copy. Simply adjusting the copy constructor to
> look like the following:
>
>
>
> // -----------------------------------------------------------
>
> MyGeometry(const MyGeometry& myG, const CopyOp& co):
> Geometry (myG, co),
> _verts (myG._verts) {
> }
>
> // -----------------------------------------------------------
>
>
>
>
> ...gives me a ref_ptr that references data in the old object, naturally.
> Currently, I'm able to work around and get the desired behavior, but I
> want to make sure everything is proper before implementing a lot of
> stuff wrong and having the submission rejected because of little weird
> things like this. :)
>
> You can see a real world example in action here:
>
> http://code.google.com/p/osgwidget/source/browse/tags/0.1.5/src/Widget.cpp#70
>
>
> > Robert.
> >
> > On Feb 18, 2008 5:10 PM, Jeremy Moles <[EMAIL PROTECTED]> wrote:
> > > I have a quick question that I may be over-thinking, of which I have yet
> > > to find a simple answer.
> > >
> > > Imagine that I have a class Derived from osg::MatrixTransform--let's
> > > call this osgWidget::Window. In my derived Window class, I have a number
> > > of osg::ref_ptr<> objects referencing various things that get added to
> > > the Window object itself, and which I keep around for ease of use
> > > elsewhere in the API.
> > >
> > > I want to provide suitable copy constructors (and am required to do so
> > > by using the META_Object macro, thankfully), but I'm beginning to see a
> > > definite problem when setting the pointers in the "new" copies ref_ptr
> > > object. Usually I can come up with clever tricks to do so, but generally
> > > it's not very straightforward--which leads me to my main question: is it
> > > generally bad design to keep ref_ptr's around like this when designing
> > > classes that will directly derive from OSG objects? Using
> > > osg::CopyOp::DEEP_COPY_ALL ensures that I will get a full copy of the
> > > subgraph, which is certainly the desired behavior, but I'm not entirely
> > > sure I know the best way to easily set any internal ref_ptr's to the new
> > > subgraph after copy other than--like I mentioned earlier--clever
> > > tricks. :) Below is an example of one such abomination:
> > >
> > >
> > >
> > > // Here we're in the copy ctor()
> > > Window::Window(const Window& w, const CopyOp& co):
> > > MatrixTransform(w, co) {
> > > ColorArray* c = dynamic_cast<ColorArray*>(getColorArray());
> > >
> > > if(c) _c = c;
> > > }
> > >
> > >
> > >
> > > ...where _c is my osg::ref_ptr<ColorArray> object, and where
> > > getColorArray() works because we're using DEEP_COPY_ALL and we assume
> > > all of the geometry was deeply copied into the new object.
> > >
> > > I really feel like I'm missing an easier way to do this...
> > >
> > > _______________________________________________
> > > osg-users mailing list
> > > osg-users@lists.openscenegraph.org
> > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
> > >
> >
>
>
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