Problem rendering NURBS [maya 6]

[NeonLeopard]

Howdy,

I've just decided to start modelling with NURBS for a while rather than polys, BUT when i render NURBS all the edges are sharp and there are gaps great gaps between sufaces (espcially planar NURBS surfaces. This is mostly a problem after filleting (circular mainly) and trim operations. I've changed render for NURBS to maximum in the RENDER>SET NURBS TESELATIONS, and that helps a little but there are still gaps (fig.3 below), the problem is worse in a shaded viewport.

I've attached an example below.

Also, because this information might be important, when i fillet i apply a curve to surface to allow for the trim operaton, the curve that the fillet produces is NOT smooth (green line in Fig.1),could be a cause. can't tell

Any advice or help would be greatly apreciated. thanks

PS. UV mapping to NURBS anyone?? know of any advice on textureing NURBS?? tutorials perhaps. thanx

[pecenipicek]

it happens a lots of times with the friggin nurbs... tho with some tweaks you can gain some rather nice results... too bad my truespace doesnt have any nurbs regulations... meh...
life aint fair

[Black]

Pecenipicek

It is a comon issue and no simple work arounds until you get to really understand conitniuity in Curves.. in the Gnomon workshop there is a very short free writtn tutorial on the subject which you could give a look.
But basically what it is is that you have a curve that is bashing it's way down..(the curve mentioned being any isoparm from the semi sphere) and then a fillet or anything else that corresponds to it. And unlike the polygons. The content of a Nurbs surface does not really end at where you see the shaded object as in Polygons. What you have to ensure it that the curve ends match to the begining of the next surface. I can try and illustrate it if you are not able to grasp it like this.

As for your second question...
The concepts of NURB'S and EASY TEXTURE do not walk in the same path.. such a factor does not really exist.
The cool things about a NURBS surface is to have conssitancy all through out the model. So painting on it is easy..
and also if you have a tilable texture (Like a specific forums CD's full of textures) you can just slap it on the sphere or what ever and it will look fantastic.

But when it comes to paint on this part or that part ONLY... nope. sorry.

My personal pipeline is to project textures onto a plane that matches the dimensions of the NURBS surface/Surface group. And then convert the projection to a file texture.
The only draw back here is the fact that you need to remember that the fit to object group option once again does not fit it to what you see shaded. But where the CV's end.
There is an intresting tutorial on such a work-flow with an older version of MaYA here
The method there has less dependency of your personal artistic talents as it allows you to be able to correctly calculate how the texture should apply.

Hope this helps

[NeonLeopard]

Thank you Black! To be honest, i had an idea that it was my modeling techniques/habits that were causing these problems to occur. I had to check there wasn't any other reason though! (after a lot of experimenting and "monitor punching" of course)

I'll have to get back to playing around and experimenting till i get it right then.

Thanx for the nurbs texturing advice. (i'll save that for later) and thanx for the tutorial links, and of course, your time!!

Cheero!!

[pecenipicek]

well... i dont think i quite understand you...
well... i think ill try to find some more tutorials. anyways thanks

[Black]

Hmmm ok.. I guess words can make it abit too technical.

Here I prepared a series of images that might aid you...
(Once you get an Idea, you may want to check on Gnomon about there explanation)

[Black]

And to make it a bit more clear.. I am going to try to demonstrate it on a surface...

Like this is an examople of topping off a clyinder. With an intent to have it spherical:

[Black]

If you shall notice..

Only by scaling the top CV's together. I don't really get a good enough result.

But like in the curves sample... If I alighn the last two CV's per Isoparm... then I get a much better result.. the surfce"Flows"

[Black]

I hope this could make it a bit more clear for you.


Even if you think you got it.. it would be wise to experiment on this manner, if not to search for other tutorials aswel.

[NeonLeopard]

Thanks again black! above and beyond!!

That extra explination has helped some!! making the curves continuous has tidied most things up. cleaning up the arrangment of my cv.s has helped also! I've still got some errors with the trim after fillet thoughit still gives me jaggedy edges, but i'll follow your advice above and try and fix it. (i'll have to check the cv's on the curves created by the fillet, but they seem to be ok)

[pecenipicek]

that was for nurbs right?
well... i know that stuff... its just that in ts6.6 you cant really control how many iterations(sp?) you put on your nurbs...
and my problem is this:
i try to nurbs a cube, and i get a nicely rounded up cylinder(in a manner of speaking...) and the model is good in the wireframe and stuff.. but when i render it, i see the little spaces between poly's... i think that this has something to do with the 4 points of the quadrangle not being on the same plane, but i think that shouldnt have mattered... so i try fix bad geometry... no good result...

[pecenipicek]

*cough*
beware... pics are 1280x1024... not too big in size around 200k only, but theyll probably be far larger than your screen
http://img.photobucket.com/albums/v8...eenShot001.jpg
see the little problems(and look at the polycount AKA faces
http://img.photobucket.com/albums/v8...eenShot002.jpg
problem gone, but look again at the polycount....

[Black]

Okey.. you are really loosing me here.

Yes we are talking about NURBS surfaces here. Thought so were you. But 'faces'?!

I have only studied TrueSpace and yet never used it even through it is vry affordable... So I am just going to throw out some sudgestions to what I THINK might be going on.

As I know it: By default a NURBS cube is created as a group of 6 surfaces rather than a single mesh... There hould be an option to generate a single meshed cube wtihin the option Panel.
This may sound a bit TOO simple. But since you are staring off with a cube primitive.. can this be your problem?
In any case.. wasn't there something called a 'GlueTool'? for connecting peaces? Did you try that?(Since you are talking about faces here)

Another thing that comes to mind would be to seperate the surfaces or remodel them with a gap and use something like the BlendSurfaceTool. It does create a smooth connection depending on your settings.

When your shape is such a primitive form (no offence.. I mean as: 'not complex') I can not understand why you are left struggling with it.
I actually feel extra weard here trying to answer a TrueSpace topic in a forum where a very well known namein it's community, Andy-Kay, is a moderator.

[pecenipicek]

well... i meant faces as the polygon count in the pictures...
oh well.. .so using NURBS cube should be a better option than using a ordinary primitives for nurbs modelling?
well... i might try that... ill posts some results later this day