Re: [osg-users] Visitor concept. No finalize?
If it's so important it get called automatically, why can't you run your finalize code in the destructor? On 1/25/2011 3:36 PM, Sam Warns wrote: Hi, that is exactly the point. My RemoveXVisitor SHOULD remove nodes but since it is not possible to do that in apply and there is no finalize method that gets automatically called after accept has finished, it is only possible to remove nodes by providing a custom member which the user must call manually. That is what I am talking about, it is not possible for a Visitor to do certain things without having the user explicitly call members of it after the accept call. I did not demand a finalize method and I understand Robert's statement that flexibility is achieved by relying on the user. Never the less would a finalize method decrease any flexibility and power of it. (Btw: I have never experienced that handing over responsibility to the user (which is the developer at this point) produced any good results, but this is only my experience) Thanks, Sam -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=35965#35965 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org -- Peter Amstutz Senior Software Engineer Technology Solutions Experts Natick, MA 02131 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Visitor concept. No finalize?
This would require the user to be aware of the fact that the Visitor has not finished its work after dtor is called. This is even more user unfriendly in my point of view. Sam -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=35988#35988 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Visitor concept. No finalize?
Hi Sam, You can't remove an object from it's a parent in a apply() method as this would invalidate the iterators of the calling code (the traverse() method that calls the node-accept() which in turn calls the apply()). It's safe to remove the children of a node you are passed in a the apply method, but not removing that node from it's parent. Another approach is to collect the list of nodes you want to remove in list during the traversal using the node visitor than have a method you call after traversal that does all the operations on the nodes, this way you can avoid invalidating iterators. The second half of your post I couldn't make any sense of so can't comment on this. Robert. On Tue, Jan 25, 2011 at 7:26 AM, Sam Warns the_vincu...@hotmail.com wrote: Hi, I was writing a Visitor that performed an extraction of certain elements from a scenegraph. My first try was to remove the nodes in question from their parents directly in the apply method which lead to some exceptions. So what am I doing wrong? I mean I would except some finalize method which is called when the visitor is finished. Currently the only remaining function is the getter function for the nodes, that should be extracted. So in apply I have stored references to the object which I can only extract when using the getter so that the removal logic can be executed. This works so far but if I do not call the getter no extraction code is executed and nothing really happened. What am I doing wrong? Thank you, Sam -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=35941#35941 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Visitor concept. No finalize?
Hi Robert, the second half of my post is about the second option you was talking about. The apply only gathers the nodes in question and does nothing else then there is another method that performs the removal from parent. But the issue with that is, that if I do not call this method, no removal is done. That was, what I was talking about. The visitor finished its work but as long as the user do not call an additional method the removal from parent has not been done yet. I was hoping for a finish method that is automatically called after the visitors work has been finished. This finish method could then perform the necessary removal operation (or any other). Thank you! Cheers, Sam -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=35944#35944 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Visitor concept. No finalize?
Hi Sam,
You have complete control over what you do before and after traversal,
there really isn't any need to have a finalize method as it would only
restrict what users can do over what they can already do.
If you wanted an finialize method in your visitor then just write a
method like:
MyVisitor : public NodeVisitor {
void apply(...) // all my apply overrides your need...
void process(Node* node)
{
// do what you want to initialize the visitor prior
// to traversing the scene graph
node-accept(node);
// do what you want after traversal
}
};
MyVisitor myvistor;
myvisitor-process(node);
The visitor implementation is deliberately designed to allow you to be
flexible, it's up to you how you want to go about implementing the
details for the purpose of your application.
Robert.
On Tue, Jan 25, 2011 at 10:21 AM, Sam Warns the_vincu...@hotmail.com wrote:
Hi Robert,
the second half of my post is about the second option you was talking about.
The apply only gathers the nodes in question and does nothing else then there
is another method that performs the removal from parent.
But the issue with that is, that if I do not call this method, no removal is
done.
That was, what I was talking about. The visitor finished its work but as long
as the user do not call an additional method the removal from parent has not
been done yet.
I was hoping for a finish method that is automatically called after the
visitors work has been finished. This finish method could then perform the
necessary removal operation (or any other).
Thank you!
Cheers,
Sam
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http://forum.openscenegraph.org/viewtopic.php?p=35944#35944
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Re: [osg-users] Visitor concept. No finalize?
Hi Robert, I am aware of the possibility to define my own methods in the visitor but the point I was trying to explain is, that if I apply a visitor on a scene I would except that this visitor has finished its work after calling the node-accept(myVisitor) If I have a RemoveXVisitor and I as the user and not the writer of it use this visitor as I am used to use them by Code: RemoveXVisitor v; node-accept(v); I would expect that the Visitor has done it's work, which it actually didn't since there is no finalize method I would need to write: Code: RemoveXVisitor v; node-accept(v); v.doTheJobActually(); So there is a discrepancy between what I would except from a visitor after it was passed to accept and what a visitor is able to do in it's apply method Greetings Sam -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=35950#35950 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Visitor concept. No finalize?
Hi Sam, I simply don't get why your are expecting things from the NodeVisitor that it isn't intended to provide, and what you can very simply provide yourself. There are many examples of NodeVisitor's in action in the OSG please do a search through the code base. Robert. On Tue, Jan 25, 2011 at 11:34 AM, Sam Warns the_vincu...@hotmail.com wrote: Hi Robert, I am aware of the possibility to define my own methods in the visitor but the point I was trying to explain is, that if I apply a visitor on a scene I would except that this visitor has finished its work after calling the node-accept(myVisitor) If I have a RemoveXVisitor and I as the user and not the writer of it use this visitor as I am used to use them by Code: RemoveXVisitor v; node-accept(v); I would expect that the Visitor has done it's work, which it actually didn't since there is no finalize method I would need to write: Code: RemoveXVisitor v; node-accept(v); v.doTheJobActually(); So there is a discrepancy between what I would except from a visitor after it was passed to accept and what a visitor is able to do in it's apply method Greetings Sam -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=35950#35950 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Visitor concept. No finalize?
Hi Robert, I suppose I expect that because let's say a RemoveGroupsVisitor should remove Groups from a given graph, when I apply this visitor to a scene by Code: RemoveGroupsVisitor r; scene-accept(r); I personally would expect that now the groups are removed, which they are not by the limitation of the apply methods Regards Sam -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=35952#35952 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Visitor concept. No finalize?
Hi Sam, Your expectations are unreasonable, please them recalibrate otherwise you are going to constantly disappointed that everything in the world doesn't conform to you prior conceptions. In the case of the NodeVisitor where you are seeing a limitation, it's actually a positive and deliberate feature. The OSG's NodeVisitor is extremely powerful and flexible, this is achieved by handing over responsibility to the developer and makes as few assumptions as possible. With this it does have usage patterns that you have to follow, there are plenty of examples that illustrate it's use, and I have given you examples and explanations. Robert. On Tue, Jan 25, 2011 at 11:54 AM, Sam Warns the_vincu...@hotmail.com wrote: Hi Robert, I suppose I expect that because let's say a RemoveGroupsVisitor should remove Groups from a given graph, when I apply this visitor to a scene by Code: RemoveGroupsVisitor r; scene-accept(r); I personally would expect that now the groups are removed, which they are not by the limitation of the apply methods Regards Sam -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=35952#35952 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Visitor concept. No finalize?
On 1/25/2011 4:34 AM, Sam Warns wrote: Hi Robert, I am aware of the possibility to define my own methods in the visitor but the point I was trying to explain is, that if I apply a visitor on a scene I would except that this visitor has finished its work after calling the node-accept(myVisitor) If I have a RemoveXVisitor and I as the user and not the writer of it use this visitor as I am used to use them by Code: RemoveXVisitor v; node-accept(v); I would expect that the Visitor has done it's work, which it actually didn't since there is no finalize method I would need to write: Code: RemoveXVisitor v; node-accept(v); v.doTheJobActually(); So there is a discrepancy between what I would except from a visitor after it was passed to accept and what a visitor is able to do in it's apply method If your RemoveXVisitor doesn't actually remove anything, but instead collects references to X (that you might remove later with a separate operation), then perhaps you should consider changing the name of the visitor to CollectXVisitor to more accurately describe its purpose, so that other developers don't get confused about what it does (as you are describing above). -Paul ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Visitor concept. No finalize?
Hi, that is exactly the point. My RemoveXVisitor SHOULD remove nodes but since it is not possible to do that in apply and there is no finalize method that gets automatically called after accept has finished, it is only possible to remove nodes by providing a custom member which the user must call manually. That is what I am talking about, it is not possible for a Visitor to do certain things without having the user explicitly call members of it after the accept call. I did not demand a finalize method and I understand Robert's statement that flexibility is achieved by relying on the user. Never the less would a finalize method decrease any flexibility and power of it. (Btw: I have never experienced that handing over responsibility to the user (which is the developer at this point) produced any good results, but this is only my experience) Thanks, Sam -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=35965#35965 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
