[vtkusers] Drawing patches on surfaces

[marcin.krotkiewski]

Hello, all

I am struggling with the following z-fighting related problem. I have a 
surface colored by some scalar data. I would like to display small, 
solid-color patches exactly on that surface. Currently, the result looks 
bad: I see the underlying surface through the patches in random places, 
and I get flickering when rotating.

I was thinking to use polygon offset to fix this problem, but it looks 
like the polygon offset parameters are global, not per-mapper. What I 
would need is to push the underlying surface 'backwards' wrt. the 
overlying patch, so they must have different offset parameters.

Intuitively, I would have thought that the order in which the 
surface/patch is plotted could somehow help to solve the problem, but I 
did not manage to find a satisfactory solution.

Could anybody help?

Thank you!

Marcin