Splines aka NURBS?

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Messenjah
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Joined: Thu Nov 03, 2005 8:03 am

Splines aka NURBS?

Post by Messenjah »

Well,


I have been finding myself very comfy with Blender's interface until I discovered how limiting the spline system appears to be. I can't figure out how to make complex objects with it such as character torsos' or super smooth fighter.

In one tutorial I read, it stated that subsurfs have replaced the spline system but I generally don't like the subsurf system at all. There doesn't appear to be a way to reduce the polycount accuratly enough for low-poly work and I can't find a way to accuratly model with this system without creating massive ammounts of completely pointless faces. :\ I also don't see any way to convert the catmul subsurf in a way that I can define each individual vertice on each face that the catmul creates.

I've also read that there is no way to accuratly define cloth and certain models using catmul because too many vertices are generated.

This is why I REALLY like the NURBS system in most programs. But I can not, for the life of me, figure out how to use Blender's NURBS system accuratly. Why do I like it so much? Because I can more accuratly define exactly how complex the geomertry is on my mesh and on the fly. If too many faces are generated in a certain area, I can always convert it to a polygon when I'm done creating a basic shape in NURBS and easily re-define it.

There appears to be no way to extrude a control segement from a control point if it is allready connected to two or more control segment. Only if it is connected to one, will this work.

You also can not remove doubles with these control points so if you can't merge them into a single control point.

From what I can see, you can not manually connect a segment to more than two points.

You can not extrude multiple control points.

You can not delete points if they are connected to two or more segments.


So, my question is, HOW DO YOU MODEL WITH THIS?? I can do this accuratly in most programs but I can't for the life of me figure this out?

I would say that the spline system REALLY needs an overhaul.

LetterRip
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Joined: Thu Mar 25, 2004 7:03 am

Post by LetterRip »

The answer is that Blenders NURBs are currently really limited and are not recommended :). The slightly longer answer is that the nurbana library was integrated into Blender and will probably be included after 2.40 and thus you will probably start to see the nurbs tools improve greatly.

LetterRip

osxrules
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Joined: Wed Jun 02, 2004 6:34 pm

Re: Splines aka NURBS?

Post by osxrules »

Messenjah wrote:I can't find a way to accuratly model with this system without creating massive ammounts of completely pointless faces.
Actually, that's one of the reasons why subsurfs are better than NURBs. If you try to add some local definition to a NURBs object, you find that you have to add much more geometry/CVs because they have to unwrap to perfect squares to maintain UVs.
Messenjah wrote:I've also read that there is no way to accuratly define cloth and certain models using catmul because too many vertices are generated.
I don't understand what you mean about too many vertices. In subsurf modelling, you make a polygon structure that defines your object and set the level of subsurf. The base model can be as high or low resolution as you like. That is pretty similar to the way NURBs work except that you use CVs instead of verts and U and V tessellation settings instead of subd level.

I started out with NURBs and when I was using them, I thought I would never use anything else. Maya's subdivision modelling was a pain in the ass and that's why I used NURBs there.

But when I started with characters and things, NURBs was just so awkward and unintuitive for me. I think it's a personal thing which type you like best. But for example, a NURBs cube in Maya is formed from 6 separate NURBs planes. I didn't like that at all. I also didn't like that you cut holes in NURBs by drawing surface curves and trimming them.

When I think of the time it took to do pretty simple objects and how long it takes me now using SubD, I haven't looked back. I don't even use NURBs curves, I prefer beziers.

I would recommend giving subd another go. They're really not that bad. There are features that help you use even less vertices too like subsurf creasing - this is like NURBs weighting I think. By all means post a specific example of one of your models that you are having trouble with to see if maybe there is a way any of us can help.

If you absolutely must have NURBs, then Blender is not where you should look at the moment. But then I'm not sure which tools are good. I've used Maya's NURBs and it has quirks too, I've heard the same about Max. I forget all the things that frustrated me about them but there were enough for me to abandon them for good.

Again, it's down to preference though. I'd say probably the two best modellers on the market are Modo and Rhino3D. Modo is subd-only and Rhino is NURBs-only. But they are expensive. Blender is actually a lot like Modo.

Messenjah
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Joined: Thu Nov 03, 2005 8:03 am

Post by Messenjah »

Well, the problem with changing the resolution is that you either have an extremely ugly low-poly object that wants to be smooth or you have this really overkill object. You can't model 2000-3000 or lower models with subsurf. Not an entire character that way at least as far as I can tell. Especially since you have to triangulate it which doubles the ammount of faces in a mesh.


What I was getting too was that someone on one of the forums was trying to create a cloth over a ball and he couldn't make it as accuratly because he had to use subsurfs to do it and he said something to the effect a subsurf system doesn't work with a mesh like that because of too many vertices or something of that nature.


I may give it another try but I don't see how I can create a torso with nice rounded arm and neck sockets in under 500 polys with subsurf.


You mentioned that you don't like how a NURBS mesh fills holes... so you cant make two more clicks to delete the faces you don't want after you convert it to a polygonal mesh?

I have tried other programs but the problem is that I can't afford any of them for personal use, even though I can use them. Personally I loved Max's spline system. I could build anything I wanted to with it. :) From what I saw of Maya's it wasn't too bad either.

Also, with a subsurf mesh, I can't figure out how one would go about editing tiny little details on a mesh and converting the entire mesh to something useable as a low-poly mesh?

From what I have seen of subsurf, you can't make low-poly models ment for games at all because you can't bring the resolution down far enough. Low poly work is pretty much, mostly what I do since I work mostly on mods and games (I have actually worked for a game company).

That is what I like about NURBS, you can bring it down to low poly and still remain at least reasonably close to the shape you wanted to create. You may have to add a bit of detail but you have a nice mesh to work off from. :)

LetterRip
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Joined: Thu Mar 25, 2004 7:03 am

Post by LetterRip »

You might try creating the mesh initially with subsurf then use pyredux to get it fairly low poly. Or you can use loop delete to reduce your poly count.

LetterRip

osxrules
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Joined: Wed Jun 02, 2004 6:34 pm

Post by osxrules »

Messenjah wrote:Well, the problem with changing the resolution is that you either have an extremely ugly low-poly object that wants to be smooth or you have this really overkill object. You can't model 2000-3000 or lower models with subsurf. Not an entire character that way at least as far as I can tell. Especially since you have to triangulate it which doubles the ammount of faces in a mesh.
I'm modelling a character exactly in that range right now with subsurf but that's using mostly quads, which would double it for a game character. But I'm trying to model parts you probably wouldn't in a game like fingernails and toenails and detailed ears.

Even so, I just experimented with the decimate modifier in 2.4 and it works amazingly well. It reduces any model to a predefined tri count on the fly. It used to be that you had to apply it once and you had to accept it but now that it's a modifier, you can see the reduction result in real-time and change it.
I may give it another try but I don't see how I can create a torso with nice rounded arm and neck sockets in under 500 polys with subsurf.
Excluding hands, I did it in 418 polys. My hands are 280 each. Also, I modelled a belly button, clavicle and shoulder blades, which you might not for a game.
You mentioned that you don't like how a NURBS mesh fills holes... so you cant make two more clicks to delete the faces you don't want after you convert it to a polygonal mesh?
Yes, you're right but if I made a hole that way, I'd have to continue using polys. So I just use polys from the beginning.
Also, with a subsurf mesh, I can't figure out how one would go about editing tiny little details on a mesh and converting the entire mesh to something useable as a low-poly mesh?
Just add face loops the same as you would on a NURBs object. Mainly around orifices or points of interest. Say you want to make a nipple for example. You model the breasts in a circular fashion so that to add detail at the tip of the breast, you just add a small poly loop.
That is what I like about NURBS, you can bring it down to low poly and still remain at least reasonably close to the shape you wanted to create. You may have to add a bit of detail but you have a nice mesh to work off from. :)
Again, the decimate modifier should cover that. Basically, add a subsurf modifier to your low poly object to get it really smooth and then add a decimate modifier to reduce this smooth object to a defined amount of tris. You can do this all in real-time. Then when you are happy with the number of tris and the shape of the mesh, just apply the modifier.

Messenjah
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Joined: Thu Nov 03, 2005 8:03 am

Post by Messenjah »

Hmmmm maybe I just need to know where I can find some good tutorials on subsurf. Anyone know of some? The only one I really went through was Graybeard's subsurf tutorial. All it taught me was how to make a chess pawn that had an extreme ammount of detail. When I tried catmul on a square, all I could get was a PERFECT sphere with a massive ammount of polys, something like 96 polys. :\



I think the biggest thing splines need is some way to remove doubles on the endpoints and some way to design in more than one axis and a decent way to taper it. For instance, I was trying to make a coil last night. You design a coil like a spring. I had to use a path because it was the only way I could design anything with it that was along more than 1 or 2 axis. I need to have a way to design nurbs/beizier shapes in all axis at any given time. What I mean by taper is to shrink it down toward on end of the curve to a specific radius, so that is shaped more like a funnel but remains a coil.

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