[vtk-developers] FYI: Parametric functions...

[Will Schroeder]

Here's an update on some new classes going into VTK: the 
vtkParametricFunctions.

+ A long time ago Bill L. checked in the Cardinal and Kochanek splines. 
They are very nice, and I've been wanting to better integrate them into 
VTK. For example, provide ways to easily interpolate 3D points (in the past 
you had to create three splines for each of x-y-z, etc.) Since that time, 
I've also been working on a framework to allow different splines to be 
plugged in (hence the vtkSpline superclass).

+ In the mean time the whole widget thing exploded, and I've been fortunate 
to receive funding this year to add some medical segmentation/registration 
widgets to VTK, including some spline-based widgets.

+ Also, Andrew Maclean from the land down under has contributed a sweet set 
of parametric functions based on his knowledge of differential geometry.

Thus the stage is set for some activity here. The parametrics are set up 
similar to vtkImplicitFunction, in that vtkParametricFunction has 
subclasses that implement different parametrics (which may be of 1D -> 3D 
in dimension). There is a class in Graphics/, 
vtkParametricFunctionTessellator, that can produce triangulations of any of 
these functions (this is analogous to the relationship between 
vtkImplicitFunction and vtkSampleFunction).

There is a lot of potential here. Besides adding in different splines 
(interpolating and/or approximating, 1D and/or 2D). it is possible to add 
in things like a  parametric function for tessellating the shape (i.e., 
interpolation) functions of vtkCell (and subclasses). Nice for 
self-visualizing VTK...

Will