Trouble with NURBS

# 1 18-09-2011 , 09:20 PM

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I am probably missing a simple concept, but nurbs modeling has eluded me for quite some time. I'm not letting it win this time, but I need help.

I have the bulk of my object. A claw built out of multiple lofted elliptical-ish curves. Naturally, lofts end with a hole. I want to round that hole off, which means that Cap Nurbs and Lofting Final Iso to a zero-scale closed-curve (both cheats I've used before and hated the outcome) won't work. So I built this cage out of 3 curves. All points that seem to intersect DO intersect (snapped to curves).

1) I cannot, however, figure out how to make a surface on this VERY SIMPLE cage.
2) After that I'll loft the open surface area's iso to this cage's elliptical-ish curve. Will that work or is fillet the right tool for the final connection step?

Thanks!

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# 2 18-09-2011 , 10:47 PM

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What you want is to create a patch. You can do this by using Surfaces>Square. You must have 4 curves to do this however. (Think of quad polygons)

So you would need to cut up your curves so that each patch will be a quad.

Take a look here for an example: https://www.creativecrash.com/tutoria...part-1-3/page2

Imagination is more important than knowledge.

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# 3 18-09-2011 , 11:38 PM

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Tried to build it with patches but couldn't get the curves to split properly. I'm just kind of hacking away until I get it right, but I'm sure there are workflows out there that make sense and have been extensively tested. So, attached is what I'm trying to cap with a rounded end. As you can see, the end is currently a single open iso. What process would you guys use to cap it? Thanks again.

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# 4 19-09-2011 , 12:30 AM

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Just a quick question. Why are you using NURBS? You would save yourself a lot of trouble using polys.

If I ever build something with curves, I'll loft them, then convert them to polys, and finish it off that way.

Imagination is more important than knowledge.

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# 5 19-09-2011 , 12:35 AM

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I've always wondered what the place for nurbs was. Do most people finish in poly? I always have started in poly then moved to subd but I wanted to learn some nurbs, since I'm ignoring 33% of Maya's modeling tools, which just seems like a bad idea.

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# 6 19-09-2011 , 03:25 AM

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Using the curves you have created in the initial post and the curve from the isoparm at the end of the surface you can do 4 boundary surfaces which can be rebuilt and attached.

This will create kind of a reshaped half nurbs sphere at the end of the surface. The down side to this is you will have a pole at each end.

Here is the idea...

The curves are numbered 1-8. The boundary surfaces are created by picking the curves in the order shown. (ie the top front surface is a boundary formed from curve 1, 2 and 4 (1-2-4). The order you select the boundary curves in is important the pole will be between the first two curves selected.

After creating the four surfaces (and rebuilding them) attach them to create a single surface.

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Last edited by ctbram; 19-09-2011 at 05:02 AM.

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# 7 19-09-2011 , 03:28 AM

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Whatever studio I've been in, NURBS is just ignored. It was a lightweight way of getting smooth surfaces, when machines had problems with extremely high poly subdivisions, however a lot of modern pipelines don't even support them. In fact, Mental ray, in the background, converts all NURBS into polys before rendering. Polys are fast to learn and edit. NURBS has it's place in other industries such as Automotive design and manufacturing, but they're using specially designed NURBS software. Maya is lacking in this area. I don't even remember when the NURBS toolset in Maya was last updated. Just because it's there, doesn't mean you have to use it user added image

I know a lot of people that use the lofting function, but they always finish up in polys.

Imagination is more important than knowledge.

Last edited by NextDesign; 19-09-2011 at 03:33 AM.

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# 8 10-12-2011 , 02:57 AM

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as an aside, all nurbs modelers change the smooth surfaces you see into polys to render, even in the viewports when you turn shading on

it's really about the modeling and editing process--do you need the accuracy of nurbs curves as you model? if not, modeling in polys will probably do you just fine. for rendering, its all poly when all is said and done

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# 9 10-12-2011 , 05:23 AM

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I would not discount the value of nurbs so readily.

If properly implemented and maintained, which unfortunately they are not in Maya, they can be a very powerful tool. Especially for hard surface modeling. There is a very good reason why nurbs are used as the primary and in most cases only method to describe surfaces in automotive, aircraft, mechanical, and industrial design software and it is not simply because they are light weight. The precision and control one has using nurbs to build accurate complex compound surfaces far exceeds anything one could possible hope to achieve using polygons and a purely polygon modeling workflow.

There are complex surface shapes that would almost be impossible to model accurately without nurbs curves and surfaces. Other packages have splines and spline patches and nurms and in the case of 3ds max and modo and c4d and lightwave they are being not only maintained but enhanced because these companies have the foresightedness to realize their value.

For Autodesk and alias before them to ignore nurbs curves and surfaces for the last ten years is in my opinion is a major mistake and is very short sited. Were they to drop nurbs support entirely that would be the last straw for me and I would certainly switch to another modeling application.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

Last edited by ctbram; 12-12-2011 at 12:22 AM.

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# 10 12-12-2011 , 12:17 AM

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sorry, I didn't want to discount the value of nurbs, in fact I love using nurbs in rhino--sometimes I think confusion comes from people not saying what they're planning to use them for. For instance doing a character model, it just doesn't make as much sense to use nurbs, but a character modeler might be confused by advice or a comment from an industrial designer regarding nurbs on a forum somewhere. And I probably jump to conclusions too, thinking that most people using maya are doing character work...when that's probably not true either.

Last edited by LML; 12-12-2011 at 12:25 AM.

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Trouble with NURBS

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