Maya-Lofting from projected curves on surfaces

[murdok]

Hello all.

I'm new. Thanks.

Well, I create a nurbs curve, and project it on a nurbs shape (one that used to be a perfect circle, but tweaked ever so slightly) . Then, I select the projection, and then the original shape. Loft. And it seems the edges loft to cross-over sections. As if being pinched in the middle...why?

http://www.vi2.com/getFile/100030.jpg

Here is a link to the image issue I'm having. Thanks.

[campbell]

if you have a look at the structure opf your projCrvOnSurf you'll notice its not the same as your projected crv, this makes for nasty lot results, requiring you to do some cleanup/rebuilding/reversing of crvs to keep their uniformity. you may also find that projecting crvs across surface seams will give you unpredictable results. essentially - go in and cleanup projected results.

[murdok]

INteresting.

I don't understand why it is not working. It seems to work when I use a standard nurbs circle. The results here work well and predictable. Though, If I tweak it, it seems to want to connect opposite side cvs.

I don't understand how I can clean up that wreckage in the image. It's overwhelming, and I don't even know how to start.

A projected curve on surface, forms an isoparm from which i can loft to other nurbs curves. This should work, as a normal loft works. Damn wavefront. JK.

I will focus my learning elsewhere for now. I simply don't understand.

[joojaa]

Let me try to explain this wery simply...

Whan you project a curve onto a surface i ceases to be that curve alltogether. It becomes a projection, wich doesent have to have any correlation to the original parametrisation, except on a surface space spesific levell. Wich is broken once you extrude bacuse maya needs the world space cordinates for this work.

Also if the surface has a seam under the projection then its even worse.

Instead extrude the thing onto the surface and ger intersection curves then trim, and rebuild the surface with trim convert option. should yeald the result you want (but its not neccesery that your maya verion has the tools beeded for this)

[murdok]

Ok. I get what you're saying.

Don't project, but instead use intersect>trim...then from the hole left from the trim, use it's isoparm to loft onto another nurbs circle? I'll try it as soon as I get home, thanks.

[campbell]

nope, build your loft surface such that it intersects your other surface, then interesect the two so you can trim away the unwanted portions. this is if that is what you were intending to do, trimming a hole. but perhaps you wernt. if its a static model, and you dont see these potentially trimable bits, then who cares? pehaps you actually want to be animating the second surface, and have your loft surface updating? (in which case, see my post. that is, project your crv, kill history, then clean your crv up by rebuild or other methods so that it matches the structure of the profile crvs you will be lofting it w).

ps. there is a difference between isoparms, trim edges, and curves on surface.

[murdok]

Actually, you're not getting what I want.

I want to, let's say, create a torso from nurbs, then connect the nurbs arm to it, by projecting the edge arm curve onto the torso, then lofting them together.

I understand about delete>all>by type history.

And I understand the difference between isoparms and edges, as well as curves.

[campbell]

righto. then i want bother pointing out your accidental missusage of their meaning above! and i wont bother pointing out the case above which applies to your situation, or that its likely that using this method may not be the best approach to character construction, and that a patch modelling approach might be better suited and something you might like to look into.

[deke-kincaid]

check out these tuts:
http://www.mtmckinley.net/tut1.html
http://www.mtmckinley.net/tut3.html

You need to approach this from a different method then how you are doing it. They way your doing it will only look good in a still but as soon as you try to animate it, your in for a nightmare.

[murdok]

You won't bother? Did I rub you the wrong way? What did I do, other than explain to you that I knew the difference FYI, so that you could speak in a manner less n00bian.

I fully understand that creating a character is done more often than not with polys (as they do in game houses). But I was just giving an example of lofting projected curves to other curves.

Thanks for your help. If you plan on being sarcastic, or snappy...please, don't bother even posting. I mean no harm.

,

[campbell]

yeah, true it did seem a little growly. i thought that after posting. my appologies. you did nothing to provoke the devil w/i me! i really mean no harm either! (thats why i did bother, to mention that i wouldnt bother saying things i was saying anyway! ).

regarding the stupid nit picky pedanticness on the use of words, i was just reading your :
" then from the hole left from the trim, use it's isoparm to loft onto another nurbs circle?"
and i wanted to point out that isoparms are distinct from trim edges, i guess i shoulda said just that! isoparms being the edge to edge fellows that do a whole surface direction at same paramater value (iso, same), a trim edge being a curve that exists in the surface's UV space (an underworld). thats all. whilst you may alredy know this, and it was just a slip in terminology, i bring it up only because i think it worth while to get things straight for yourself, and we can all help educate each other!

there are plenty of threads on this forum that will talk more about the reasons why people generally stay away from trims, jsut do a search on trims and you'll be surprised.

the basic problem being that they dont respond well to deforming animation of the surfaces w trims on them (often the case for characters, unless they are robots), this is due to the manner in which a trimmed nurbs surface is tesselated into polygons for rendering. if you turn on 'display render tesselation' for a trimmed nurbs surface, you'll see how the triangles are layed out around the trimmed edges...play w the different settings and see how you can make it fit a little nicer, then pop, say, a lattice on the surface and animate the pnts on it a little, or just drag 'em around, and watch how the tesselation flips around the place ...imagine that on a seams of a character. notice how slow it is to claculate.

trims more of a place in hard, static models. so how do you go about using nurbs then? how do you join an arm to a place where there are no openings (poles), no nice isoparms to connect onto? this is where the idea of patch modelling comes in. a technique that is used to overcome the inherent problem w nurbs, that they are four sided. search that one up too, probably already familiar w the idea, if anything by reading tutes beaker posted!

i hope this has been of some value to you! you'll find heaps of details if you search the archive. also do check out the tutes here on this site, especially the nurbs tesselation one when you start getting into patching your models.

good luck! and merry vibes!

[murdok]

No problem at all man. Don't even worry about it.

Using trims is the best way to cut out doors and windows from a house or what not, that is the way I was trained (via Maya 4 Fundamentals book and CD).

That stitch tutorial link that was givin will certainly do some good. It is basically what I wanted to know.

I admit now, that I didn't know what a trim curve (on the surface) was actually called, I figured however it should link (loft) to another isoparm of an already lofted surface. Blah, no problem. I'm still a Maya n00b.

Thanks for your help.