Hi rabbit:

Very thank you for all.

Well. I had to post my impressions about Michael´s suggestion, but I am a bloody lazy :-)

In fact, I didn´t probe delaunay plugin because I read that it doesn´t generate a nurbs surface but a polygonal one.

My idea was to work over the surface drawing roads on it, defining levels for platforms where buildings were placed, and then I need to keep the nurbs surface for made operations like trim, use boolean commands and more....

Another thing. The model I showed was deformed, and the Z scale was multiply x 10, for aprreciate the reliefs, but it´s not a mountainous area.

Well, those were my initial ideas.

After read to you, I have the ideas more clearly, but I still have the problem that I get a not-nurbs surface. Well, the other idea is to model the buildings in MoI and export them to Su, but....I have a new problem, and it´s that at the end I couldn´t render the result.

Then, I prefer to model all of them in Rhino and export them to Blender. I don´t know....

Anyway, the method for export from AutoCAD to MoI to step is very useful to me.

Very thank you