Re: [osg-users] Copy Constructor Advice
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_castVec3Array* where you need access to the array, or to
provide a convenience method to getVec3Array() { return
dynamic_castVec3Array*(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 +, 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_ptrVec3Array _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_castColorArray*(getColorArray());
if(c) _c = c;
}
...where _c is my osg::ref_ptrColorArray 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
Re: [osg-users] Copy Constructor Advice
On Tue, 2008-02-19 at 09:44 +, Robert Osfield wrote:
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_castVec3Array* where you need access to the array, or to
provide a convenience method to getVec3Array() { return
dynamic_castVec3Array*(getVertexArray()); }
Yeah, you're right about this; the duplication probably is
inappropriate, and is exemplified by issues here with it. :)
Would this solve this problem?
Yes indeed! I will make it so...
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 +, 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_ptrVec3Array _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_castColorArray*(getColorArray());
if(c) _c = c;
}
Re: [osg-users] Copy Constructor Advice
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.
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_castColorArray*(getColorArray());
if(c) _c = c;
}
...where _c is my osg::ref_ptrColorArray 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...
___
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