[vtkusers] adding a function to a vtk class

[Wolfram H Volpi]

Is there a way to add a function to vtkVolumeProperty using an object
factory?

I think that a function can not be added because:
	1) vtkVolumeProperty is a derived class of vtkObject.
	2) the vtkVolumePropertyWithAddededFunctionObjectFactory passes
the pointer vtkObject*
	3) the pointer can only reach functions that are declared in the
base class vtkObject.

Therefore an object factory can not add a new function to
vtkVolumeProperty.  Is my conclusion correct?

I will be using the added vtkVolumeProperty function in a tcl script.
If I do not use an object factory, I will need tcl wrapper code for the my
new class vtkVolumePropertyWithAddededFunction, which means I will need a
source installation and recompile.

Is my understanding correct or is there another way to add a function to
vtkVolumeProperty? 
What is the easiest way to add a function to vtkVolumeProperty?

I am new to tcl, C++, vtk, and development, so I will appreciate any feed
back.

Thank you,
wolfv.