> there is not in Rhino 4 something like "repair" function or
> "Optimize" for the plan triangulated?

I think there is a command "MergeAllFaces", which will combine NURBS surfaces that are coplanar into one larger trimmed plane.

You could run that on those stones to simplify some of them, you should be able to do this with the Rhino eval version, you can find it here if you need to do that: http://www.rhino3d.com/eval.htm

- Michael