[vtkusers] writing new transform classes for logarithmic axes warping

[N Smethurst]

Hello VTK users

So as a few of you know (and probably most of you don't), I have been 
writing a KDE based user orientated front end for VTK over the past 
months. In this application, I am also including a more standard plotting 
framework for people wanting to do data visualisation within the context 
of numerical applications (i.e. easy plotting of lines and surfaces within 
the context of an advanced axes object).

In order to provide this, I've been trying to write new transform classes 
which provide the warping necessary (within a vtkTransformPolyDataFilter 
instance) for my axes objects. My transform objects need to do linear and 
logarithmic scaling in various ways (cartesian, spherical, cylindrical).

Unfortunately, I can't seem to make much sense of what virtual methods I 
need to reimplement from the abstract transform. I tried reimplementing 
these:

void InternalTransformPoint(const float in[3], float out[3])
virtual void InternalTransformPoint(const double in[3], double out[3])

but they don't seem to be called at any point.

Is there any chance of someone giving me a summary of the steps required to 
write a new vtkAbstractTransform derived class? I would be most grateful!

Regards

Nick