[vtkusers] vtkBoxWidget handle size bug or feature?

[Berti Krüger]

As i have seen by walking through the source code of vtkBoxWidget.cxx the
method for resizing the handles vtkBoxWidget::SizeHandles() is first called in
the constructor 

vtkBoxWidget::vtkBoxWidget()
{
  ...

  // Define the point coordinates
  double bounds[6];
  bounds[0] = -0.5;
  bounds[1] = 0.5;
  bounds[2] = -0.5;
  bounds[3] = 0.5;
  bounds[4] = -0.5;
  bounds[5] = 0.5;
  // Points 8-14 are down by PositionHandles();
  this->PlaceWidget(bounds);

  ...
}


by the method 


void vtkBoxWidget::PlaceWidget(double bds[6])
{
  ...
  this->SizeHandles();
  ...
}



The method void vtkBoxWidget::SizeHandles() looks like this:

void vtkBoxWidget::SizeHandles()
{
  double radius = this->vtk3DWidget::SizeHandles(1.5);
  for(int i=0; i<7; i++)
  {
    this->HandleGeometry[i]->SetRadius(radius);
  }
}


And it is also called in void vtkBoxWidget::OnLeftButtonUp(), void
vtkBoxWidget::OnMiddleButtonUp() and in void vtkBoxWidget::OnRightButtonUp().


So if you click on the widget the line 

double radius = this->vtk3DWidget::SizeHandles(1.5);  

is executed a second time after its execution in the constructor which results
in resizing of the spheres (factor 1.5 again).


Anyway. I have now subclassed vtkBoxWidget and have overwritten the
SizeHandles() method and it works now how i need it in my project.


Thanks again to the vtk developers for making vtk opensource.


Berti Krüger


PS: If anyone can help me with some enlightenment regarding the default
behaviour of vtkBoxWidget i would still be glad (e.g. bug or feature?).
 


Am Wed, 7 Feb 2018 06:21:55 +0000
schrieb Berti Krüger <berti_krueger at hotmail.com>:

> It seems i am not the only one who doesn't understand the logic behind the
> sizing of the vtkBoxWidget handles:
> 
> http://massmail.spl.harvard.edu/public-archives/slicer-devel/2011/006000.html
> 
> "Hello,
> 
> I am using a vtkBoxWidget, and it seems the size of the handles depends on
> the ValidPick (to know if handle has been picked or not) (and on the
> renderer to. We have to set a current renderer before calling PlaceWidget.)
> 
> So, when I am creating the box, ValidPick is 0 because handles have not been
> picked yet.
> The size of the handles is calculate with:
> 
> return (this->HandleSize * factor * this->InitialLength);
> 
> 
> But, when we resize the box, ValidPick change to 1 (on
> OnLeftButtonDown() (same for middle and right button) ), and the size
> is now calculated like this:
> 
> return (this->HandleSize * factor *  sqrt(radius) );
> 
> 
> InitialLength has been replaced by sqrt(radius) (defined on
> vtk3DWidget::SizeHandles)
> 
> But sqrt(radius) is different from InitalLength.
> 
> So, when we create a vtkBoxWidget, handles are small, and when we resize it,
> handles are bigger.
> 
> 
> Is this normal, or it's a bug ?
> 
> Thank you.
> Laurent."
> 
> 
> 
> Am Mon, 5 Feb 2018 10:00:16 +0000
> schrieb Berti Krüger <berti_krueger at hotmail.com>:
> 
> > Hello Everyone!
> > 
> > I am currently using a vtkBoxWidget in my project (VTK 8.1). After i
> > created the vtkBoxWidget, the size handles (= vtkSphereActors) have not been
> > picked yet and are small and nice. 
> > 
> > But, when I resize the vtkBoxWidget (smaller or larger, it doesn't matter)
> > or simply click on it, the handles get bigger (radius increases) and stay
> > this way.
> > 
> > They sometimes tend to get so large that they are piercing the mesh and
> > visually adding themselves to it, which is annoying. And they never get
> > smaller again, sometimes they get even larger.
> > 
> > When i zoom out by large amount and then zoom in again, the handles get
> > normal ( = small) again.
> > 
> > Is this the intented behaviour, and if so, what is the purpose of it or is
> > it a bug ?
> > 
> > 
> > Thank you very much in advance.
> > 
> > 
> > Berti Krüger
> > 
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