Nurbs

# 1 03-06-2008 , 07:31 AM

Registered User
Join Date: Jun 2008

Location: Los Angeles, CA

Posts: 229

Ok, so I used 3ds Max for years, but never got very good with it. I absolutely did NOT learn anything about nurbs and my poly skills were so-so at best. I'm switching to maya because now I'm in college, and I am going to take advantage of the huge academic discount they (autodesk) offer for college students: Maya Complete for $400.

Anyway, I'm now sort of in crunch mode, relearning all the little bits I got from 3ds, but trying to start fresh and understand how things work, including nurbs. So:

1) How do you merge/combine two cvs on a nurbs curve? As in, make a smooth transition? I created a curve that loops itself, but the loop point is still hard.

2) Best method of subtraction with nurbs? I've heard that booleans are a bad idea, but I don't know if that source is legit or not. The trim tool deletes faces but doesn't allow (I think) for the subtraction I'm looking for: I'm modeling a soda can, (trying) and on the top there is an indention in a figure 8. I'm trying to create that indention, and have had the hardest time doing so.

3) Extruding a curve via loft. Currently doing so ends with no caps. I know I could increase the loft spans and scale the ends to 0, but that seems inefficient. Is there a better way?

Thanks.

--
Peter Srinivasan
Producer

Quote

# 2 03-06-2008 , 07:37 AM

Subscriber
Join Date: Jun 2004

Location: Nottingham

Posts: 344

Unfortunately I can only answer your first question but maybe it still helps.

1) How do you merge/combine two cvs on a nurbs curve? As in, make a smooth transition? I created a curve that loops itself, but the loop point is still hard.

Originally Posted by

The answer is...You dont.
You leave a gap between your last point you need to place and your first one and end the curve making via hitting enter, you then go up to your surfaces menu set and under Edit Curves goto Open/Close Curves this will fill in that blank area and smooth your curve off

Quote

# 3 03-06-2008 , 09:38 AM

Super Moderator
Join Date: Dec 2006

Location: South FL

Posts: 3,522

@ [3]I think "loft" means something different in Max than it does in Maya, so the phrase "extruding a curve via loft" doesn't make sense to me, since extruding and lofting are two different operations in Maya. You can cap it off by grabbing an isoparm and doing a planar operation.

- Genny
__________________
::|| My CG Blog ||::
::|| My Maya FAQ ||::

Quote

# 4 03-06-2008 , 11:59 PM

Senior Software Developer
Join Date: Jan 2005

Location: Livingston, Scotland

Posts: 1,701

Re: Nurbs

Originally posted by petersrin

1) How do you merge/combine two cvs on a nurbs curve? As in, make a smooth transition? I created a curve that loops itself, but the loop point is still hard.

2) Best method of subtraction with nurbs? I've heard that booleans are a bad idea, but I don't know if that source is legit or not. The trim tool deletes faces but doesn't allow (I think) for the subtraction I'm looking for: I'm modeling a soda can, (trying) and on the top there is an indention in a figure 8. I'm trying to create that indention, and have had the hardest time doing so.

3) Extruding a curve via loft. Currently doing so ends with no caps. I know I could increase the loft spans and scale the ends to 0, but that seems inefficient. Is there a better way?

Originally Posted by

1) The only way to "merge" the cv's of that curve is to cut the curve at the desired CV and then have 2 curves and then use the Attach Curves tool, make sure its set to blend and not connect. And then I would advise using the Rebuild Curve Option and setting it to the desired number of CV's you will need to get the correct shape.

2) Boolean Operations are a Polygon Tool, for Nurbs I would suggest using Isoparms to cut out the top and then create each curve in the correct place and then select the top IsoParm and the new Curve and use the Loft Tool, then repeat this for the remaining curves. Once thats done you would need to fill in the hole anf that can be done by using the Planer Tool.

3) To use the loft tool efectivly in Maya you need multiple curves and the select the 2 curves and use Loft, then select the last curve and again and then the next one and select Loft and so on... Once done you attach the lofts by using the Attach Surfaces tool.

TBH, I would rather model it in Polygons and then convert to Sub-D. Sub-D has all the benifits of NURBS with very few of the drawbacks.

Hope this helps.

Chris (formerly R@nSiD)
Twitter
When the power of love overcomes the love of power the world will truely know peace - Jimmy Hendrix

Winner SM VFX Challenge 1

3rd Place SM SteamPunk Challenge (May 2007)

Last edited by R@nSiD; 04-06-2008 at 12:02 AM.

Quote

# 5 04-06-2008 , 05:56 AM

Registered User
Join Date: Jun 2008

Location: Los Angeles, CA

Posts: 229

Thanks all, I've begun to get the hang of things... a bit. I've got a subd mesh right now, and I made the mistake of creating the whole thing even though I wanted it to be symetrical. I'm having trouble deleting one half. For some reason, I'll select vertices and hit delete, and they'll just be sitting there making fun of my stupidity, instead of winking out of existence.

--
Peter Srinivasan
Producer

Quote

# 6 04-06-2008 , 10:13 AM

Registered User
Join Date: Jun 2004

Location: Cleveland, Ohio (USA)

Posts: 1,541

try selecting the faces and deleting them.

Accept no substitutions.

Quote

# 7 04-06-2008 , 10:39 AM

Registered User
Join Date: Jun 2008

Location: Los Angeles, CA

Posts: 229

I was apparently not clear :< I have tried all formats of deletion that I know, selecting each kind of component as well. They all translate, but no deleting. Thanks.

--
Peter Srinivasan
Producer

Quote

# 8 04-06-2008 , 09:03 PM

Super Moderator
Join Date: Dec 2006

Location: South FL

Posts: 3,522

Did you even try going into poly mode and deleting faces?

- Genny
__________________
::|| My CG Blog ||::
::|| My Maya FAQ ||::

Quote

# 9 04-06-2008 , 09:13 PM

Registered User
Join Date: Jun 2008

Location: Los Angeles, CA

Posts: 229

Like I said, I tried every obvious deletion method:

In both standard and poly mode, deleted faces, edges, vertices.

Tried a boolean with a large box and the object to physically subtract half.

I would just start that part of the model over, but I have a feeling there is something very simple I'm missing in a slightly less obvious place, perhaps some form of locking mechanism built into maya that wasn't present in 3ds. I've run into other problems too: it seems random, but sometimes I won't be able to translate vertices at all, even though they are not locked.

So, perhaps it's due to the process I used to model it:

I lofted a bunch of nurbs curves and then converted to subd. Any possible way that could freeze anything up? It's quite strange.

--
Peter Srinivasan
Producer

Quote

# 10 04-06-2008 , 10:41 PM

Senior Software Developer
Join Date: Jan 2005

Location: Livingston, Scotland

Posts: 1,701

Im a bit stuck at what your problem is, without seeing the issue for myself.

Normally I would convert from NURBS to Poly first and then do a little additional work by refining and adding any geometry there. Also I would do the deletion of the faces I didnt need first and then I would be converting to Sub-D. And then duplicate the model...

Try converting from Sub-D to Polygons now and then remove these unwanted faces, then convert back to Sub-D.

Chris (formerly R@nSiD)
Twitter
When the power of love overcomes the love of power the world will truely know peace - Jimmy Hendrix

Winner SM VFX Challenge 1

3rd Place SM SteamPunk Challenge (May 2007)

Quote