[vtkusers] vtkTransform concatenation

[David Gobbi]

See comments below:

On Thu, 13 May 2004, N.E Mackenzie-Mackay wrote:

> Hey david,
>
> 	Her eis a follow up question.
>
> 	Right now I have a method that returns a transformation.  What I would
> like to do is concatonate the result with a transformation that already
> exists. e.g.
>
> 	Say the method that returns the transformation is called "method" and
> a already existing transform is called "t"
>
> 		......
> 		t->concatenate(method(parameters))		//concatenate the retuned
> transformation with 't'
> 		....
>
> 	If I understand vtk garbage collection correctly, to avoid any memory
> leaks I would have to do this instead:
>
> 		.....
> 		vtkTransform temp;
> 		temp = method(parameters);
> 		t->concatenate(temp);
> 		temp->Delete();
> 		.....
>
> 	Is there a better way to do what I am doing?

Nope, there is no better way that I'm aware of.  If the method creates a
new transform, you have to treat that new transform exactly the same way
you would treat   temp = vtkTransform::New().

 - David


> Thanks again for your help :)
> Neilson
>
> On May 12, 2004, at 6:15 PM, David Gobbi wrote:
>
> > Hi Neilson,
> >
> > VTK's garbage collection takes care of this for you.
> > When you concatenate 'b', the reference count of 'b' is
> > incremented so you can safely call delete on it,
> > it will stick around until 'a' is deleted.
> >
> > To answer your questions:
> >
> > 1. if you delete 'a', then 'b' will only be destroyed if you have
> >    already deleted 'b' once before.
> >
> > 2. if you delete 'b', it won't actually be destroyed until after you
> >    have deleted 'a' (or until you have called "Identity" on 'a').
> >
> >  - David
> >
> > On Wed, 12 May 2004, N.E Mackenzie-Mackay wrote:
> >
> >> Quick question.  Say I had two vtkTransform's: 'a' and 'b'
> >>
> >> if I concatenated a with b: a->concatenate(b);
> >>
> >> 	1. if I deleted 'a' would this delete 'b'.
> >> 	2. if I delete 'b' would this screw up the pipeline for 'a'
> >>
> >> Thanks,
> >> Neilson
> >>
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