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CurtJ

07-12-2007, 05:33 PM

I'm using maya to model a simple nurbs ring which isn't a fully consistent shape around the shank.
The bottom section is subtley different from the top, and I want to blend it throughout the sweep.
As I see it, the grunt way to do this is to make the profile curve and extrude it around a circlular curve, then bit-by-bit adjust the CVs proportionally. I'd rather have something like the birail tool do this though, so it's a nice blend, which will leave me with the option to easily edit the profile curves once the surface has been made.

Here's the curves set up ready to extrude:

http://www.curtjackson.co.uk/img/ring/1.jpg

As you can see, I've made the two slightly different profile curves - one at the top, one at the bottom.

Now I was intending on creating a birail surface which would blend from one profile into the other, and back - forming a nice ring shape ready for me to tweak using the curves, but I was wrong. The birail 1 tool wants only one profile curve, and two rails, which doesn't work with this setup. I end up having to use the rail as the profile curve, and the profiles as the rails instead, which gives me this mess:

http://www.curtjackson.co.uk/img/ring/2.jpg

I'm sure there's an alternative to this, but I just can't put my finger on it.

Like I say, I can always do it manually but it'd save me a lot of hassle if I could create it then use either profile curve to edit the surface sweep.

Can anyone suggest a solution for this? Any help greatly appreciated.

Oh, here's (http://www.curtjackson.co.uk/download/ringCurves.mb) the curves if they're any use to anyone (v8.5)

CurtJ

07-13-2007, 07:28 PM

Hi again, thanks to the people who had a look at this. I managed to achieve the result I was after using a different method, which I'll explain here in case anyone else is trying something similar, or just for people who are curious.

I realised the clue was in the name - birail. Two rails, not two profiles, so I tried another method, and it works well enough for the purpose.

I used three profile curves in a row - the centre one representing the bottom of the ring, and duplicate end curves which will result in the seam at the top of the ring, which will be explained in a moment.

Like this:
http://www.curtjackson.co.uk/img/ring/3.jpg

The curves were selected in order, and a loft created with them resulting in this bar shape...
http://www.curtjackson.co.uk/img/ring/4.jpg

Then, retaining all construction history, a bend deformer was applied and rotated to align. The curvature was set to 3.1 (default scale is used here - the grid you can see in the persp view above is the standard 12 units across) which forms an open loop, leaving a gap at the top:
http://www.curtjackson.co.uk/img/ring/5.jpg

Then a 'close surface' was applied with a blend bias of 0.5 to ensure symmetry, and the basic ring shape is complete:
http://www.curtjackson.co.uk/img/ring/5.1.jpg

As the construction history has been preserved, the original profile curves can be reshaped and tweaked as desired (through x and y, in this case) and the surface will react accordingly. You will get unexpected results if you move the curves or curve components through the z plane, or if you add or remove curve components (CVs, EPs etc).

Lower profile curve with some fiddling about:
http://www.curtjackson.co.uk/img/ring/6.jpg

http://www.curtjackson.co.uk/img/ring/7.jpg

Here's the model in it's penultimate stage, with a shape cut from the top, where the stone is to be placed:
http://www.curtjackson.co.uk/img/ring/8.jpg

I'm going to attempt to make the stone from degree 1 nurbs. Should be interesting, and as for lighting it... well, I'll be back with some questions, I'm sure.

Hope someone has found this useful, or even just interesting. I've just read the 'Does anyone use NURBS anymore?' thread, so who knows...
:)

Curt.

frodo2975

07-13-2007, 07:53 PM

thanks for sharing your methods. I'm trying to learn maya and I need all the help I can get

johnnymoha

07-24-2007, 06:02 AM

That's a great way to go about it. Thanks for the tip.

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07-24-2007, 06:02 AM

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