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 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

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 From:  Hammer
3855.8 In reply to 3855.7 
Hi Micheal,

Now I understand! thank you for the very detailed example. I assume the same concept would apply to lofted shapes etc. I am going to slog on with the car model and post results and questions.

Thanks,

Steve
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 From:  Michael Gibson
3855.9 In reply to 3855.8 
Hi Steve, I'm glad that helped!

> I assume the same concept would apply to lofted shapes etc.

Yup, the same thing applies there as well - if you have some kind of irregular shaped boundary you probably don't want to try to loft directly to that boundary initially, instead you'd want to make a larger smooth surface and them trim it to produce the final boundary.

Here are a few previous posts with some similar cases where building an extended shape and then cutting it was the best strategy:

http://moi3d.com/forum/index.php?webtag=MOI&msg=3795.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=3321.17
http://moi3d.com/forum/index.php?webtag=MOI&msg=3105.7


You usually want to do this kind of strategy when you've got some kind of surface shape that has looks all nice and smooth but then has an edge in it that suddenly cuts the shape off. It is easy to recognize this when the cutoff is an internal hole in the surface, but the same thing applies when the cutoff is slicing the outer edges of the surface as well.

- Michael
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