From:  Michael Gibson
3855.7 In reply to 3855.6 
Hi Steve - so here's a bit of an example for how you could build a more simple extended surface with Network, and then use Trim to make cutouts rather than trying to build the initial surface directly to a more complex outline right all in one shot (which then tends to distort the surface, particularly with sharp corners in the outline curves causing corresponding sharp features in the generated surface).

I've attached the 3DM model file if you want to look at the curves.

So here's the kind of curve structure where it's a more extended and more simple sheet:

Then build a Network with that:

Now to produce the cutouts you actually cut the surface - make a cutting curve in a side view like this:

In the 3D view you can see how the surface and the 2D cutting curve relate to one another:

Then select the surface and use the Trim command, and use the 2D curve as the cutting object - that will project the curve onto the surface and slice it, pick this area to discard:

And you can see how you can get sharp cutouts and details like that, but have a smooth surface:

A lot of times if you have irregular outlines especially with sharp corners on it, putting those details in by trimming can be a lot better than trying to incorporate the irregular outline directly into the initial surface construction.

This kind of strategy of "build an extended shape and then cut it" tends to be pretty frequently used in NURBS modeling, it's one of the things that makes NURBS modeling significantly different from poly modeling.

Sometimes it can help to think of it more like an actual physical construction process where you'll have some piece of stock that then gets pieces of it cut away.

- Michael