[vtkusers] Which data structure to choose?

[iontichy at mac.com]

Hello,

I'm very new to the whole VTK toolkit stuff. I am trying to use it for scientific visualization. At the moment I am trying to figure out, how to approach the following problem in terms of data structure:

I create 2D/3D clusterings of data sets. I need to plot the 2D/3D clusters on top of the original data set. The clusters should have distinct colors (color staying the same for one cluster).

I am already writing out the underlying data sets as .vtr (rectilinear grid) data. How I am thinking about how to approach the clusters themselves. Which vtk data structures should I use? The clusters represent subsets of the original data set, but are often very small.

Can I use the rectilinear grid format again, only writing out  a subset of points? Or will this approach force me to provide all points for the grid, regardless of how many are actually used? 

The other route I was considering was to use vtkQuad / vtkVoxel (for 2D/3D respectively). I mostly understand how to create the data structures, but how would I assign them a property for coloring? 

I would be grateful for any advise in this matter. VTK can be a little confusing/intimidating at first. Thanks!