[vtkusers] vtkPerlinNoise and vtkImplicitSum added to vtk nightly

[Michael Halle]

Dear vtk users,

I've checked in two new classes to the vtk source tree;  they are
available as part of the nightly source release or CVS.  With
only minor modifications, they should also work with vtk 3.x.

vtkPerlinNoise is an implicit noise function based on Ken Perlin's
famous characterization of a computable, non-periodic noise of
characteristic scale.  Frequency, amplitude, and phase of the noise
can be adjusted.

vtkImplicitSum calculates a new implicit function based on the
weighted sum of several input functions.  You can use it to create
more elaborate noise functions of several frequencies, or you can add
a "geometric" implicit function and deform it with noise.

There are two tests (Filtering/Tests/Tcl/ImplicitSum.tcl and
Filtering/Tests/Tcl/PerlinNoise.tcl) and one example
(Modelling/PerlinTerrain.tcl) for your inspection and enjoyment.


						   --Mike