# Architectural Semi-Submersible Design

Single span non-rational NURBS curves and surfaces have exactly equivalent Bezier curves and surfaces of the same degree/order.

Bezier curves and surfaces have exactly equivalent single span non-rational NURBS curves and surfaces.

Single span rational NURBS curves and surfaces have an exactly equivalent rational Bezier curves and surfaces of the same degree/order.

Rational Bezier curves and surfaces have exactly equivalent single span rational NURBS curves and surfaces.

Bezier curves and single span NURBS curves have Degree+1 control points.

Bezier surfaces and single span NURBS curves have (DegreeU+1)*(DegreeV+1) control points. DegreeU is the degree in one parametric direction and DegreeV is the degree in the other parametric directions.

Any muli-span NURBS curve can be converted exactly into a set of Bezier or rational Bezier curves.

Any multi-span NURBS surface can be converted exactly into a set of Bezier or rational Bezier surfaces.

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Nurbs are indeed very complex to be comprehensive for me.

Yep I can confirm it. I would say it like this. If you want a extremely clean surface model it is faster and easier to do in ICEM.

And as you pointed out the reason is its fundamental different approach of approximation instead of interpolation. Whatever you do in ICEM (if you run in it in Design mode) you anneal a given surface patch to whatever you want to do. You want to offset, so you define the surface properties first and then it tries to get as close as possible to the computed point net. This gets rid of the post process like you have to do in Rhino after any operation. And ICEM approximation algorithms are one of the best. This becomes especially valuable for complex blendings. Difficult corner blends (if you know the surface layout of common corners like T, Y,X and other junction blends can be created extremely fast and flexible in a complete manual process. Newer ICEM versions even create some corner blends in highest quality automatically.

It feels more like construction than design and of course this âas-close-as-possibleâ mindset, requires you to check anything twice. Does the continuity match? The curvature may match, but there is a positional mismatch. On the other hand ICEM is the only tool which gives you enough analytic power to actually match a surface only by moving control points. On a difficult blend, optimizing the matching manually is extremely powerful.

My experience from automotive design is that if you want highest quality you ask a ICEM specialist and if you want it quicker you choose someone using Alias.
Now Alias becomes better in class A from day to day. Some even switched from ICEM to Alias already. And yes the GUI and UX in general is not the best. I think why ICEM is so common in automotive industry, is because it had been developed in strong cooperation with engineers and designers while doing everyday work. And as a specialists tool itâs not good in other things, but quite straightforward for anything you do for creating a car skin. Latest development however focused more on project management, since OEMâs usually see modelling as contract work. So they need mechanisms to evaluate others work, instead of improving workflows. It scares my how much is outsourced nowadaysâŚ

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By the way: ICEM crashing can be strongly reduced by preventing operations on faced/trim boundaries and also by list manipulation. Whenever you do something like this make sure to save before.

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Thanks for the tip! Iâll keep an eye out for this.

I always thought it crashed exactly when the surface release deadline was dueâŚ

Really cool design and well modeled. Itâs harmonious.
Could you show some sections too?

Thanks @lois !

Thereâs no engineering/naval architecture to this one, itâs purely a concept with an initial GA, so there wonât be much to see in the sections unfortunately.

In fact I seem to have lost my initial GA somewhere (hopefully itâll still be on a hard disk somewhereâŚ) but below shows a snapshot of a more simplified one used to plan the spaces.

But, as I say, this is just a concept done for my own entertainment!