[vtkusers] QT/VTK application: Access violation on vtkTransform inside a QTimer event

[John Drescher]

> Thanks for the tip.  It looks if the vtkTransform is indeed there, but the
> (internal) inverse transform of the vtkTransform is NOT.  In particular,
> through debugging, it is the following line that raised the access violation
> error:
>
> //----------------------------------------------------------------------------
> // Need to check inverse's MTime if we are an inverse transform
> unsigned long vtkAbstractTransform::GetMTime()
> {
>   unsigned long mtime = this->vtkObject::GetMTime();
>   if (this->DependsOnInverse)
>     {
>     unsigned long inverseMTime = this->MyInverse->GetMTime();    <==========
> this line
>     if (inverseMTime > mtime)
>       {
>       return inverseMTime;
>       }
>     }
>   return mtime;
> }
>
> Is this a bug in vtkTransform/vtkAbstractTransform, in which the inverse
> transform is not being allocated/updated automatically?
> I'm using vtk 5.6.1.
> any help is very much appreciated,
>

Is this->MyInverse a valid pointer when it crashes? Look at that in
the debugger.

John