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View Full Version : NURBS help needed desperately!!


Mattrne
07-11-2002, 08:18 PM
Hello everyone, I'm desperate for a bit of advice. I'm building a character in Maya in my spare time, to try and learn some of the basics of Nurbs modelling. I've used trims and fillets of varying types to connect the various parts of my model together, such as legs to hips arm to shoulder etc, but I've hit a bit of a stump - I need to attach a sphere I'm using as the basis for this guys shoulder, to a deformed sphere I'm using for his upper chest.

Only problem is, I'm not sure what I need to do to get it to work - I think I'll probably have to do a fillet again, but I don't know where to begin - how to project the curve on surface etc - any ideas? I've ttached a picture so you can see what I'm trying to do...

Any help would really be great!

LordGolem
07-12-2002, 11:25 AM
Hi,
I think the method you're using to model your character is actually out of the way. That's because first of all for an organic character model you shouldn't use trim as in animation deformation it's not so predictable. Trim would be good for a kind of robot, but for an organic model...

The right way to model a NURBS character is to make a multi-patch drawing curves on surfaces. Just start varyous body parts as cilinders and sculpt them then attach the various parts sitching them thogeter (a good knowledge of the stitch tool is fundamental). The method I use is first attach surfaces, rebuild, detach and theen global stitch... the result is nice and clean!

Bye

Mattrne
07-12-2002, 12:10 PM
Thanks for that! Are there any good tutorials you can recomment for this workflow? I'm a total nurbs virgin!

I always have difficulty drawing curves on surfaces - I make the surface live then try to draw on it, but I invariably seem to get screwy curves. I've gone through the help loads of times, but I always seem to have trouble!

Mattrne
07-12-2002, 12:10 PM
One more thing - you say trims are not good when animating - why?

LordGolem
07-12-2002, 02:27 PM
Trim isn't good because in the deformation when the character is bind to a skeleton it is not well predictable. Usually trim is not used for a character (the problem is similar to the boolean operation with poly).

I don't know any specific tutorial, but maybe on highend3d there are a lot of them. I'm planning to write one but I don't know when (so don't wait for me :) ). Maybe visit my website (there's also a NURBS character I'm working on in the work in progress section). GolemGraphics (http://www.golemgraphics.com)

Bye

Mattrne
07-12-2002, 02:41 PM
OK, i've tried to make the torso part live and then draw a curve on to it, but when I finish the curve, it goes all weird and does a strange kind of spiral thing (see picture). I want it to basically follow the line drawn in white, but it never closes the gap drawn in red, it just, as I say goes weird.

Is this because of the parametrization of the sphere the torso is made from? Any suggestions as to what I can do to rectify the problem?

LordGolem
07-12-2002, 03:00 PM
Yep, it demends on the parametrization... this because you are trying to draw a curve on the seam. The correct approach is to model half body at a time and then duplicate/nevative scale. Todo so don't start with a sphere but use a cylinder, put it in the front view and align it to the image plane. Make the it just 180 and nopt 360 as default. Rotate it so the opened side is aligned with the center axis. Freeze the transformations and start sculpting it trying to match the image plande.
Do that for the torso, one leg, one arm the head and so on. Then sculpt your fine details (using loft, boundary etc.). Then make the sculpted geometry live and draw curves following the parametrization and matching end points to your details. Detach curves from the surface and loft or boundary them.

It's a long process and you have to practice a lot to get a good manuality. Try and try again. Learn how to stitch using the rebuild tool, is very effective and you can obtain seamless surfaces.

Bye

DavidALam
07-15-2002, 08:14 AM
i woudln't use a nurbs shape to bulid a model in the first place i think you can get better control and shape out of a polygonal object. Just a suggestion though. Model it boxy then do a smooth on it. Then do blend shapes for animation and bind it to a skeleton.

-Dave

LordGolem
07-15-2002, 10:22 AM
He's trying to learn NURBS, so he cannot use smooth.

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