XSI/3DS Max/Lightwave users: question re: nurbs

Big Rocket

Hello all,

I wish to do some complex nurbs surfacing, as seen here, bottom picture. I ran into limitations with Maya's Birail 3+ function. Can XSI, 3DS Max, or Lightwave 3D do what I showed in the bottom picture?

In case you are wondering, I was using an engineering software, highly unsuitable for animation. But it does allow for an unlimited number of splines in the primary and secondary directions, all within a single nurbs surface.

edit: Forgot about Lightwave 3D

Thanks,
BR

ElysiumGX

I never use nurbs, but I did read somewhere that XSI lacks some strengths in nurbs. I tried to copy what you're trying to do, but can't honestly. Maybe some other XSI expert can explain why.

But, why not use subdivisions instead?

pior

Rhino can do that hands down, and more... You might be interested in trying the demo :

http://download.mcneel.com/rhino/3.0/eval/

You can go through tutorials to learn the app, but I also suggest to simply try and test the commands one by one, alphabetical order. It might sound stupid but at least you'll know what you need to know!

Hope this helps

Big Rocket

ElysiumGX: I have done modeling with push-pull polygons, sub-d's, and nurbs (a.k.a. spline cages), and nurbs can have a lot of advantages. For example, that bottom picture I talked about was done very quickly in nurbs (5 minutes, if that), but it would have taken me many times longer with sub-d's.

pior: Thanks for the heads-up re: Rhino. Quick question: Does Rhino have a decent, built-in texture mapping tool? I know Deep Paint 3D supports Rhino, but I don't feel like shelling out the extra money if I can help it. edit: I forgot to ask: Does Rhino support animations with bones/skeletons? Thanks.

MoP

I dunno, that bottom image, I could make in about half a minute in subdivided polys. I don't find NURBS very user-friendly for general modelling...

Daz

[ QUOTE ]
I dunno, that bottom image, I could make in about half a minute in subdivided polys. I don't find NURBS very user-friendly for general modelling...

[/ QUOTE ]

Agreed, I'm not sure why you're hung up on whats considered an outdated method of creating geometry BR. There are some amazing car models on cgtalk built as subdivision models.

Rakile

Nurbs are fairly powerful in 3D Max, but I could only see them as useful for simple organic objects. Making a character with nurbs is not very practical. The one I tried looked decent, but when I tried to animate it, it simply didn't work very well. I know of a way you could make a shape like that in Max, but I think it was with spline modeling.

malcolm

Use smooth proxy or subd if you want to make an organic model, nurbs are the worst all time modeling tool ever, and try animating and uv mapping them, horrible. That being said we actually use nurbs in Maya to build the terrain for ssx, but I would never consider using them for anything that is not a blobby surface.

pior

Hey BR

In fact I don't think that rhino has any 'advanced' UV mapping tool. If I remember well the UV layout is restricted to the way the shape is engineered. Like, the U and V from the texture layout follow the U and V from the surface. But I might be wrong

Besides that, what Mop says. These shapes could be done in poly rather easily. Control points in a nurbs surface are very similar to vertices in a subd or meshsmoothed volume. You won't have access to bezier-like handles but you are not restricted to a strict row/lines layout using polygon based surfacing at least.

Besides that, it's still true that Rhino deserves to be popular especially amongst model makers or anything boat-modelling related. The program can even give you the "floating line" of a modelled hull shape... Weird but cool

Big Rocket

Hi everyone,

Thanks for the heads up on SubD. See bottom picture.

FYI, I thought SubD means to subdivide an edge or face in Polygon mode. I had no idea that it refers to a whole new modeling technique. (Sometimes, I am shocked by my own ignorance, or general newbiness.) I tried it out over the weekend, and found it quite user friendly, even for a Maya newbie like myself.

Quick questions:<ul type="square">
[*]Any web links to good tutorials for building a car, plane, etc. out of SubD's? Maya's built-in tutorial goes through building a hand, but I found that a little too basic, and didn't answer some of my questions (see below).
[*]In SubD, do I build an entire model out of a single SubD primitive? Or do I stitch SubD surfaces together?
[*]When I stitch (attach) different SubD surfaces together, how do I ensure that there are no gaps in the surfaces? In 3DS Max terms, I would like to weld vertices. But in Maya's SubD, you don't manipulate the actual vertices, you manipulate control vertices.
[*]How do you unrefine a segment of the surface that was refined?[/list]

Thanks,
BR

thomasp

afaik, XSI lacks some nurbs modeling functionality that is included in its predecessor, Softimage|3D.
alias studiotools seems to be one of the most powerful packages for nurbs modeling these days. mind you, it's incredibly more expensive than maya.
same is true for other common (?) nurbs modelers used in product design. i do remember having seen downloadable evals but i can't remember the application names right now.

also afaik, you do not uv map nurbs the way you would handle a poly mesh/subd-surface. texture coordinates are automatically derived from the surface itself instead.

for creating vehicles and stuff and as long as exactness is your thing, you're probably best suited with nurbs.

Asthane

Big Rocket: What SubD's are, is an automatically smoothed cage mesh. The process is exactly the same as making a low poly model, with a few extra considerations. That said, I really have no idea what they were thinking when they made the default mode in maya a cageless display of control points. You'll probably find it much easier if you go into the SubD Surfaces menu and click "Polygon Proxy". This will show you your actual cage mesh, which you'll use regular polygon editiing tools on to edit your smoothed surface.

Daz

BR: You're absolutely doing the right thing by abandoning NURBS. However, you might not quite need to jump into full on SuBD modeling just yet. And besides, most people that use SubD's pretty much build in polys, then convert to SubD. Read the first 5 or so pages of a tut I wrote here:

http://home.comcast.net/~dpattenden/hi_poly_tut.htm

Hopefully in easy to understand English it explains the difference between true Sub-D's and subdivided ( also refered to as 'smoothed' ) polygons, and also why you would use one technique over another.

To answer your questions, don't even worry about true subdivision surfaces for now. Concentrate on smoothed polygons. Check out the tut, I think it will help. Sorry that it's so slow. Trying to figure out why and currently have no idea. Skip page 2 on research and ref.

Big Rocket

Hi everyone,

Thanks for the help with SubD. This is what I learned so far, and please correct me if I'm wrong:<ul type="square">[*]True SubD modeling requires you to start from a single SubD primitive. If you attach multiple SubD surfaces, you don't have commands to merge vertices together to close up the holes between the surfaces.
[*]When you guys talk about SubD, you mean Polygon > Smooth Proxy, which is essentially polygon modeling, with a final meshsmooth operation to increase the polycount and smoothness. You will also get SubD-like control vertices to alter the shape of the high-polycount mesh.
[*]The difference between true SubD and Smooth Proxy is that, with Smooth Proxy, if you zoom in close enough, you will be able to see the discontinuous edges between the individual polygon faces. With true SubD, the mesh is mathematically a smooth surface throughout, theoretically with no discontinuous edge anywhere -- unless you want them there with a full crease edge operation.[/list]

So, did I get it right? If I'm wrong somewhere, please correct me.

BTW, I answered most of my own questions with your help, but I'm still trying to find out how to unrefine an area of a true SubD surface that was refined. Any info?

One other thing: A long time ago, I got into nurbs because 3DS Max used to have an awful meshsmooth operation. Scott Ruggels (of 3DO and Army Men fame) wrote a nurbs tutorial in which he complained that the meshsmooth operation tended to erode the volume of a model. If he's still around, he might be happy to learn that Maya's smooth operation is much, much improved over Max's meshsmooth. Note: Just to be fair, I'm not sure if new versions of Max has improved on the old meshsmooth algorithm.

edit: Question for Asthane:
Regarding Polygon Proxy mode for a true SubD Surface, I can manipulate vertices of the cage mesh, but not the vertices of the smoothed surface, right? I was hoping for a method to attach different subd sufaces together without gaps, but now I don't think it can be done.

Thanks,
BR

StrangeFate

i haven't read everything but...

-I'm not sure what you mean with 'true SubD' ? is there a fake SubD ?. Think i have been missing something.

SubD lets you start with whatever you want (a box, a spline, an existing lowpoly model), it's just a toggle that goes from polygons to SubD and back anytime. You can usually do the same operations in SubD mode that you do in polygon mode.

-With SubD, you shouldn't need to meshsmooth at the end. I never used max, but in LW, modo or XSI you really dont want to do that as you can render anything in SubD mode just fine without having to physically meshsmooth your model to an uneditable polycount. However, depending of the mesh, meshsmoothing at the end might be necessary to have enough polygons for a proper deformation. Still, horrible thing to do.

-SubD and smooth proxy work the same, they both fake smoothness and curved surfaces using flat polygons. In SubD mode, you can zoom in and see the polygons that fake the curve too. Nurbs is true curves, SubD fakes the same effect using polygons. Since SubD is kind of interactive (it simulates a high subdivided model without actually subdividing it) you can crack out the subdivisions so high that curves will look perfect.

Some examples of SubD
You can see the 'faked' roundness and the simulated polygons. You still edit the mesh by the original polygons and points.
http://www.strangefate.com/webby/subd.jpg
http://www.strangefate.com/webby/subd2.jpg
http://www.strangefate.com/webby/medievalwire.jpg

Asthane

BR: To tell you the truth, I'm not an expert on Maya's "SubD's". I was going to go and tell you exactly how to do it, but I don't see a way for you to merge two SubD surfaces into the same object

If you do have them as one object though, all you should need to do is use the append polygon tool to close the gap on the control mesh, doing so will automagically sew together the detail mesh.

It should be said though, that if anything is "real" SubD's, Maya's SubD surfaces sure as hell aren't it The polygon's smooth proxy mode would be more like it, since there's not really much difference, and there's no BSing around with not being able to do one thing or another. By definition, anything you want to do to a SubD-type model will come out of the polygonal toolsets.

Big Rocket

Thank you again re: my misunderstanding of SubD. One nice thing I found out about Maya, is that surfaces can switch from one type to another rather easily and painlessly, e.g. Modify > Convert > Polygons to Subdiv, Subdiv to Nurbs, or Nurbs to Polygons.

Also, when I re-read Maya's built-in tutorial, it actually recommends the exact same thing you guys have been telling me: Do a low-polycount polygon model first, then use SubD to add in the details. Sounds good to me.

Thanks,
BR