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Old 12-06-2006, 05:32 PM   #1
pbman
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Default BMW Z4 COUPE - pbman

on see ing dilberts car an his passion for nurbs and my absolute lack of passwion for them i decided to try it out. so i found a tut on the net an it happens to be the same as wat dilberts making(i didnt mean to clash)

i done the ferrari tut on this site an wasnt keen on all the methods used but there was some good stuff in there that ill remember

so heres my progress i laid out the curves using EP - is CV curves better?

also take a look at the last pic wen i attach the isopams go crazy unlike all the other times wen i attach the isopams flow and i have the correct settings









c&c welcome and advice is greatly welcomed!!

:attn: :bow:
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Old 12-06-2006, 09:42 PM   #2
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Good to see you giving it a try, By the way, I'm modeling the new Z4 coupe that just came so it's a little different to the tutorial that you're following.

Anyway, to answer your questions. You use both types of curves for different situations. Bottom line, whichever curve you use, try to build it with as few CV's as possible, and as cleanly as possible (i.e. the curve should be flowing with no severe, sudden shifts in curvature). When you use the birail or squar tool, Maya is going to try to follow your curves as closely as possible, which is a good and bad thing. It's good for accuracy, but bad because if you built your curves badly, it'll still build your surface for you, but badly also (like in your picture). Maya doesn't know what your intentions are, so it just follows the guides you give it. You can rectify your problem by either building the curves again, but more cleanly, or by rebuilding the surface using the "rebuild surface" tool. Problem with rebuilding the surface rather than the curve is that you'll lose the construction history from the birail, or square.

There's so much with nurbs that can trip you up, you just have to go through and experiment. One suggestion I'd give is to put the car model aside for now, and work on something a little simpler to get used to the tools. Go through EVERY nurbs and curve editing tool that Maya has, and really get to know what everything does. That way you'll know the best tool for the job to solve a specific modeling problem. There's aspects of the tutorial that you're following that I think could have been done better/cleaner, so it's really all up to how you model, and the skills that you have in your toolbox.
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Old 12-06-2006, 10:11 PM   #3
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thx for the reply

wen u say 'built the curves badly' wat exactly do u mean?

plz be as harsh as u want i wont be affended

in tthe last pic if u divideit just to the left of the red line both of those geometry's were clean (to me) but wen i attach they go like that

also whats the diff betwenn boundary and square
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Old 12-06-2006, 10:34 PM   #4
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By building the curve badly, I mean these things: Did you use the correct degree curve to fit the job (1st, 3rd, 5th, 7th degree etc), did you place your CV's uniformly, did you check your curvature in every view port to check for severe curvature channges, did you use the curve editing tool to achieve tangency, did you use the project tangent tool to get tangency with a surface, did you tweak the cv's pixel by pixel to achieve tangency. There's a great deal involved in building a simple curve that is going to be the basis of your surface. Take all the time in the world to build the curves, because they are the foundation of everything you build.

The square tool has better tangency options than the boundary tool. Really, you could get away with never using the boundary tool.

Here's a visual example. Look at the two top curves. Visually they look almost identical right. Now look at the cv distribution of each curve underneath. Way different!! The top curve was made by making a perfectly straight horizontal curve and pulling the middle two cv's upward. The bottom was made by freehand clicking along the shape of the curve to try to match the shape. These two curves are going to produce two very different surfaces. That's what I mean about building every curve correctly.
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Old 12-06-2006, 10:42 PM   #5
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so what method is better the top or bottom curve (soz for my stupidity but i need to learn this)

i know wen i was placing them it was a pain cos they were really hard to match in all veiw port - i will look into the tangency tools ect

ill probly rebiuld them i dont mind if its gonna be better to look at an means future models will be better - also since i made those in ep should weni remake i use cv? (i am looking into basic tuts for nurbs at the mo)

but i still dont understand how u can get accuracy to 0.001cm with this as placing the curves is still inaccurate ont top of the blue prints

thx
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Old 12-06-2006, 11:08 PM   #6
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It is always better to have less cv's, so the top curve would be the cleaner curve. Whether they are EP or CV curves makes no difference. They are just two different ways to actual construct the curve, but result in the same product.

The o.oo1 comes from the tolerances built into Maya. If you look on most of your nurbs tools, you'll see a tolerance setting. This is telling Maya how accurate it needs to be when it is constructing the surface. The lower the tolerance, the closer Maya will get to following the curve or surface, depending on what tool you're using. It is not always a good idea to have it set on 0.001, as Maya will sometimes not be able to execute the surface due to limitations in the software. But none the less, the tolerance setting should always be in your mind when using nurbs.
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Old 13-06-2006, 05:25 AM   #7
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pbman,
don't give up like I did. I too have problems understanding the nurbs curve tool. However,after reading this thread, this gives me hope again. Also, I know there are a few tutorials such as 3D Total which I am going to give it a shot myself. Who knows, maybe we can help each other out.
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Old 13-06-2006, 12:11 PM   #8
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thx dilberts u really r helping out heaps here

u say to build the curves with as few cvs as poss but wen u rebuild the curve it changes the cv amounts

wen i started that tut i guessed on how to lay the curves out an such screated extra curves where not needed co i could have just use the same one an detach ect. i made the wheel arches usin a nurbs circle and adjusted the edsweep, selected the bottom two cvs and moved them - is this a good way?

i think 1 reason i initaly stayed away from nurbs is the fact i dontlike txturin them i can jst about cope with polys! all the changing to projections and tweakin lots of settin an fillin in the gaps an havin to set txt correct by manually movin the txt is anoyin espc wen i tried to txture blue

i did notice the tollerence settings on most tools an just left it as defualt which i think is 0.004cm which is fine as im doin this more for the knowledge than the final look - it will make good pratice for me since the only BIG thing i have done in nurbs is wen i made blue here

thx junkyBob for ur support - i have been usin 3dtotal for tuts but it dont work for me unless i have direct llinks to eack tut so i have to copy an paste them into word:headbang:

iwas playin with the tools last nite an i went over trim again
after projectin and trimming u getthat shape cut out but on the surface it is classed not as an isopam but as a trim edge - what is the diif does it mke some of the tools not work for it
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Old 13-06-2006, 03:36 PM   #9
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Questions answered:

When you rebuild the curve, or surface, you can dictate the number of cv's or spans in the options for the tool. So Maya will never put in any more spans than you tell it to.

Texturing can be tricky, but all the different tools available can solve 99% of problems.

I think the tolerance is usually set at 0.01 for most tools. And that is a relative setting. i.e. if you have your units set to cm, it will be a tolerance of 0.01 cm. If you have your units set to m, or inches etc. then it will be 0.01 of that unit. Relative, not absolute.

Trim edges are a whole different ball game. There's a ton of techniques to use trim edges correctly and cleanly, but it would take me too long to go over all of them. That's why I'm trying to get around to making a DVD tutorial, so I can actually talk people through the process. Writing just doesn't make things clear enough.
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Old 13-06-2006, 03:36 PM   #10
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well wat ive decided to do it continue a bit so i can learn these tools but also do research into other nurbs tools

ill probly remakee this or another car afterwards just tryin to get alot done this week as i have it off burt then back to college next week





dilberts - i can seewhat u mean about the curves on mine u can really see where some curves were badly laid

in the tut it tells u to use square but from wat ive read u need 4 curves and select in clockwise/anti direction but it s tell u to do it wen u only have 3 curves?
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Old 13-06-2006, 03:55 PM   #11
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Like I said, there's parts of that tutorial that I don't think were done that great. If you look at his surfaces, some are a little bumpy. As for the 3 vs. 4 curve question, I never, if at all possible make a surface from 3 curves. There's always a solution that keeps it to a 4 curve patch, you just have to visualize it and solve the problem. You really have to study your reference photos in detail to come up with the best solution, and always be open to scrapping all your hard work if you suddenly come up with a brilliant idea to solve a problem. I can't tell you how many hours I've wasted building a model, only to trash it after a light bulb goes off in my head, and I find a cleaner, simpler method to doing it. Don't be stubborn and impatient to have a finished product. Pick one single surface and focus only on that one little piece until you're 100% happy, then move on to the next.

Anyway, I just done with a 12 hour shift at work (graveyard shift), so I gotta get some rest. I'll check this thread again later today. See ya.
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Old 13-06-2006, 07:33 PM   #12
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lookin forward to u makin that DVD it would be great if did get the time to do it

well ive changed my mind again hat im going to do is use the curent model to pratice the fillets ect on

ive already started laying new better curves here r some shot their not perfect by a long shot an im still fiddling with the edit curves tool to get each better
ive tried to use as few cvs as possible yest keep it clean an matching the prints

will practice fillets ect later 2nite or 2 moz



persp view - it wont resize

dilberts ne comments on the new curves so far ? i really respect ne thing u say wen it come to stuff ilke this
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Old 13-06-2006, 08:32 PM   #13
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pbman,
if you are going to convert this to polygons afterwards, then I found a web site, not a car tutorial but still teaching you nurbs patching, you do not need to worry about attaching the nurbs surfaces together. Instead, after you are finished patching the surfaces, you can then convert them to polygons and then merge the vertices. The only thing I would still do before converting is to make sure that all your surfaces have been rebuilt so that all the spans line up. I am going to try this on my next model after I finish the one I am currently working on, which BTW I have posted some updates in this forum called 1970 dodge charger finally here and would not mind your comments. Just one thing I ask, be honest, I have taken really harsh crits at school, and I realize it only makes you learn from your mistakes. Also, if you do take a look, please ignore the lighting considering I am just using it to show my progress. However, at the end, I will have a car racing game, fininalized in shockwave, for you guys to play online for free.
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Old 13-06-2006, 08:54 PM   #14
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i wasnt plannin on coverting to polys but the website sounds useful though
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Old 14-06-2006, 06:05 AM   #15
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I don't think the site is that useful but maybe you could get something out of it. So here you go...

http://www.3dm3.com/tutorials/maya/head/
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