Hi milkywaif,

> Radius property is missing. Why? This is what I'm talking about.

When you do those steps, switch the "Profiles" option in the Loft to be "Profiles = Exact".

Then you should get an exact circle when you repeat those steps.


Basically when you do a Loft if you leave the default "Auto" mode for profiles, it will do an rebuild of the profiles if it sees that they have interior fully multiple knots (the juncture areas that form kinks when you drag them in Rhino).

The steps that you did results in a surface that is not quite 100% circular, it's off by something like 0.001 units.

The properties panel will only label a curve as circular (by displaying a radius value) if it's within a very tight tolerance of being a circle, more like within 0.0000001 units of circular.


It's better to make an exact cylinder by doing Extrude of just one curve, rather than doing a Loft between 2 curves. Loft has to combine multiple curves together into one single surface structure, and it tries to incorporate some simplification/rebuilding of the curves involved in order to avoid making a surface that ends up inheriting the combined structure of different curves all together.


- Michael

Michael,

> I'm not really sure _why_ you would have this situation of having curves that you were worried about being circular or not, are you doing some kind of reverse engineering task where you're trying to rebuild things from scanned data or something similar to that?

Not really. I'm building my models from scratch. I'm a long time polygon/subd modeler but I have absolutely no experience in NURBS modeling. I tried almost all of NURBS modeling software out there and decided to purchase MoI because it's very simple, yet powerful and user friendly. I'm trying to understand the logic between the tools and output geometry. As I mentioned earlier, I had some problems with my previous NURBS models. They had broken edges, distorted looking faces, bad fillets or sometimes they did not export correctly and I couldn't fix them easily. I believe it's because I used wrong choice of tools at some point. You know, sometimes you can do loft, revolve or sweep and you get the same looking result. I just want to know that I'm using the right tool when I need.

Thank you very much for your responses. You've been a great help.

Hi milkywaif, you're welcome!

Also check out here for some links to discussions and general tips for people who are coming from a sub-d / poly modeling background:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4865.2

The overall method of construction with NURBS modeling is fairly different than poly modeling, and some of those discussions are about the differences and how to sort of avoid trying to only do poly modeling type techniques in MoI.

I hope that MoI will be useful for you!

- Michael