Learning to UV... running into some problems with unfold (Maya)

aryarie

Hi all

I'm trying to learn UV mapping and I'm following the UV Mapping Workflows in Maya tutorial on Pluralsight. The tutorial provides you with an ogre character that you have to unwrap. Up until now I haven't had any problems, but I'm now working on the loincloth and no matter what I do I can't seem to get the same results and unfold behaves very strangely.

Here is the result from the tutorial:



Here's what happens when I try (though it appears to be different every time I've tried - sometimes it just comes out in a completely different shape):



I've been reading around and I think this might be something to do with the UV winding order but I'm really new to this and not sure how to go about fixing it... I'd really appreciate any help.

kwyjibo

In your screen shot, the shell is flipped (red vs blue). That could be causing problems depending what tool you're using. You could also try splitting the shell up into smaller pieces and then stitch them back together.

Ruflse

Are you trying to relax the shell without cutting it first? I can't see it very crearly by your screenshots, but if that mesh your are trying to UV is closed you are not going to get good results just by relaxing it, just because it doesn't have any opening from where it can be relaxed and create a flat UV. Think of it as a shirt, where would you cut if you would want it to lie as a planar proyection, without any part of the shirt overlapping another?

In your case it seems like it's just a simple mesh with two sides where your could cut where I show you in the image and relax each UV shell. You could also cut only from the lower or the upper part and relax it to get a single UV shell without having to cut it in two.



If it's a cylindrical piece (which it seems it is) you would also have to make a horizontal cut so it has an opening from where to relax the piece.

As I said, It's pretty hard to know by your screenshots how the piece really is, so if you could upload it as an OBJ I could help you better.

aryarie

@Ruflse I made my cut along the bottom edge that loops all the way around, which was what they did in the tutorial:



I'll have a play around with making the cuts differently as you have suggested. I'm still very unfamiliar with this process so I have some trouble figuring out where I should be cutting...

I've uploaded the OBJ here

Thanks for your help

heyeye

aryarie said:

@Ruflse I made my cut along the bottom edge that loops all the way around, which was what they did in the tutorial:



I'll have a play around with making the cuts differently as you have suggested. I'm still very unfamiliar with this process so I have some trouble figuring out where I should be cutting...

I've uploaded the OBJ here

Thanks for your help

If you watch the video a little further you'll see he makes a direct cut down vertically. This lets the mesh lay out flat like a strip.



He explains there isn't enough room for the inside UVs, and that's why when you try to unfold, the UVs freak out and try to fold in on themselves.

Think of this like trying to flatten out a sock. You cant do it unless you make a cut lengthwise. Treat UV unwrapping the same way.

Ruflse

Made some images to make it easier to understand:




This is the result, which isn't optimal and the shell I selected in the image has some harsh distortion due to it having kind of a bended shape with a pretty radical angle, making it a lot harder to relax. If you would want to avoid that distortion you could add another cut in the middle along the shell to avoid that hard angle.



This is what happens on this case if you don't add a horizontal cut:



You can download the mesh from here if you want: https://mega.nz/#!5ZYDiYqS!I7Oiv_XiYlV0QXsGneYr0u_a5T1qRo1ro8ldKzvOj14

There are some other concepts you should have in mind when making UVs, but with what I've shown in the images you should at least be able to make the mesh display a texture correctly. Hope it helps!

aryarie

@heyeye Yup, I followed up to that point, but the result I got was this:



I tried over and over again following exactly what he does but just couldn't get the same result.

@Ruflse Thanks so much for these screenshots and your help. I don't have much time this morning but I'll give your suggestions a try later on today.

aryarie

@Ruflse Cutting it as you suggested worked Thanks sooo much, it's been driving me crazy for a few days now. I still don't understand why when I follow the tutorial it doesn't work however and why he seems to get the same result with just the two cuts - one along the edge I mentioned earlier and the vertical one around the back... very strange!

throttlekitty

Maybe the tutorial glossed over a step or maybe you just missed it? Either way, the important part is that you learn and understand the process. Hopefully now you have a better idea now of how to handle cutting UVs for things you make in the future.

aryarie

throttlekitty said:

Maybe the tutorial glossed over a step or maybe you just missed it? Either way, the important part is that you learn and understand the process. Hopefully now you have a better idea now of how to handle cutting UVs for things you make in the future.

That's what I thought initially... but I've watched it back over so many times and even slowed the whole video down to make sure I hadn't just selected a wrong edge or something. I even resorted to getting someone else to watch me as I followed along! :P

I don't know if it matters much but the video is working with Maya 2015 and I'm using 2017 so I don't know if Unfold just behaves differently or something. Even then, I've unfolded UVs for the rest of the character with no trouble at all so...

But yeah... I think I have a better grasp of UVing. It seems to be the thing I have the most trouble with at the moment so I'll keep practicing.

Ruflse

No problem, glad it helped.
I don't know how it was done in the tutorial you saw but there are a lot of ways of making UVs according for what you are going to use the mesh. Sometimes it's better avoiding a lot of cuts when others it better to avoid too much distortion. You will start to see the patterns once you UV more objects.

Don't forget to give Polycount's wiki a look if you have some problems. Here are some categories that could help you:

http://wiki.polycount.com/wiki/Edge_padding
http://wiki.polycount.com/wiki/TextureCoordinates
http://wiki.polycount.com/wiki/Normal_Map_Modeling (for when you start making UVs with baking a normal map in mind).

There are some old threads here that could help in various topics too, so I recomend looking for them.

throttlekitty

aryarie said:

throttlekitty said:

Maybe the tutorial glossed over a step or maybe you just missed it? Either way, the important part is that you learn and understand the process. Hopefully now you have a better idea now of how to handle cutting UVs for things you make in the future.

That's what I thought initially... but I've watched it back over so many times and even slowed the whole video down to make sure I hadn't just selected a wrong edge or something. I even resorted to getting someone else to watch me as I followed along! :P

I don't know if it matters much but the video is working with Maya 2015 and I'm using 2017 so I don't know if Unfold just behaves differently or something. Even then, I've unfolded UVs for the rest of the character with no trouble at all so...

But yeah... I think I have a better grasp of UVing. It seems to be the thing I have the most trouble with at the moment so I'll keep practicing.

Practice makes perfect! FYI the concept of seams and unfolding hasn't changed much over the years; the unfold methods change sometimes, but smartly-placed seams never will. Sometimes with organic models, you may find it easier to make more cuts than you need at the start, you'll get a good idea after they unfold on how to piece them back together.