Why are UV unraps so distorted?

Unless it is simply a cube that gets unwrapped, the UV layout gets very whacky looking and nothing like the square surfaces on my meshes. Am I doing something wrong?


Here’s what the model looks like (and other tests):

Does anybody know how to control the manner in which the unwrapping occurs ?

I know that seam location plays some role, but that doesn’t effect how distorted the unwrapped faces become.

In the toolbar or whatever it’s called (3D view when you push T), you want to change your unwrap method. You are looking for a conformal unwrap. The option will appear then when you go do an unwrap.



EDIT: Looking closer at the above you may also want to click use subsurf data and set it to the level you are using. That will prevent the UV’s from getting distorted.

Hi Quandtum,

Thank you for the great tip! I tried it out and it helped quite a bit in most places, but it still had some strange looking results particulary around the openings:


Without seeing the mesh and the seams it’s hard to say, but I would guess seam placement is culprit (a few more seams in a clever spot or two). To help decide where those seams need to be you can look at the “Stretch”. In the UV view, on the panel that opens with the “N” key, check the “Stretch” check box. You can “Minimize Stretch” with CTRL+V and roll the mouse wheel. The value will change from 0.00 to 1.00. Chances are this won’t completely alleviate the issue though, the problem is likely with the unwrap itself. Anyways, where the stretch is the worse (non-blue) that is where your seams need to be considered.

Also, in edit mode, vertex selection, check in the header “Select”->“Non Manifold” and “Select”->“Loose Verts/Edges” and make sure they come up selecting nothing (with exception the edges of mesh for mirrors and planes, you ought know the difference when you see it). If an edge gets away from you that can sabotage the unwrap.

Hopefully that will help get warmer with finding the issue.

Edit: One last thing. From you screen if you are using subsurf on the mesh, don’t forget to check the “Subsurf” box and set it to the level (I’m guessing 2). That helps with the stretch calculations.

Hey Jeremy, thanks for the reply.

I tried both of your suggestions; and neither Non Manifold, nor Loose Verts/Edges resulted in any vertices being found. I keep looking at the seams and the stretch colorization. The seams all appear logically placed but the distortion in the mapped UV makes it tough to figure things out.

You can check out the mesh either:
test no 12.blend (581 KB) - test no 12.blend (581 kb)

or

https://sketchfab.com/kelly/recent - tests 1-12 - Why so many tests? Because there are other head-pounding-on-wall, what-in-the-hell-is going-on type things. Hope not to muddy the waters by bringing it up… but then again, the distorted unwrapping and the bizarre tonalities may be related as far as this noob can know. It’s the Sketchfab site (what a great invention!) that first reveals the unwanted and bizarre two-tone colorization but if Blender’s 3D Viewport Shading is set to Texture the problem presents itself. I still don’t know why it shows up even after I’ve purged (or so I thought) previous materials entirely - regardless of using Cycles or Blender Render.

Thanks again for the help!

Kelly

Hehe, been there done that :stuck_out_tongue:

Well, in a nutshell some of the underlying mesh topology is not working nice with where the seems are marked. In a way, where the seams are marked now they are sort of competing with the edge loop flow. So there are 2 ways forward.

1.) Using mesh (without edit) we need to add a bunch more seams. This will create more islands as well and keeping them hidden with textures can be more effort, but it depends on the textures themselves.

2.) We can add a few vertices to a few places and improve the edge flow. Once that is done we can then more easily cut along edge loops.

I’ve been looking at resolving this both ways, but to better help, which would be preferable for your project?

Edit: hidden 3rd option, we can Project View with the original mesh. This may not be subsurf happy later however.

Something to know : ngon are annoying for the unwrap in Blender, can’t say if it is a bug, a limitation of Blender or just the unwrap that is not supporting them well. But that’s unfortunately how it is.
Get rid of the ngons of a model before unwrapping will result in better unwrap by Blender.

Try this on your model to see the difference between having ngons and not having any :

  • In Edit Mode
  • Unselect the whole model
  • Click on the Face selection mode (or Press CTRL+TAB -> Faces)
  • Click on Select -> Select Faces by Side
  • Press F6 to make the operator popup, set Number of Vertices to 4 and Type to “Greater than” to have only the ngons selected.
  • Press CTRL+F -> Triangulate Faces
  • Select all the model
  • Press U -> Unwrap
  • Press F6 and set the method to Conformal

http://i.imgur.com/rGwjafV.jpg

With a better topology instead of just triangulating those ngons you could obtain something certainly even better.
Project from View some faces (and pinning them in the UV) could be helpfull too.

I was looking for ages for this information. It was quite hard to find the right words in Google. Thanks also from me, mate!

Hehe, no problem :smiley:

@ Kelly : I went fast, so this could be still be improved. It should be good enough to give you a look at how mesh topology can help with the UV’s (I sometimes add vertices just because I know they will help me with UV’s later).

I tried to preserve as much of what you had as I could, at least in form. To still get the smoothed corner effects that I think you are after, you can select the vertices in the corner and W->Smooth (which is what I suspect you had done) or you can now grab the Edge Loops and do an Edge Slide on them to relax the subsurf and let the subsurf do the work to get that round effect back.

Likewise, I did not try what Sanctuary suggested personally, but it’s good idea and good advice. That ought work and I would give that a go if the original mesh needs to be resolved.

test no 12-002.blend (648 KB)

Thanks guys for the replies.

@Quandtum - Thank you very much for this. Whatever you did resulted in not only a better unwrapping of the model with so stretch marks, but those weird texture two-tone displays are gone. It’s encouragement on different levels as I was just about - like seconds from - throwing in the towel and remodeling this stupid thing AGAIN from scratch; something which I am not opposed to doing, but it’s been ongoing since 2.28.13.

The modeling of a simple cast fitting for a shipping container has turned over the past several weeks to be first an introduction to modeling (I haven’t even gotten through Part 1 of Jon’s tutorial) and then into a topological odyssey where last weekend I thought the topo had been minimized successfully and that the ngons were well behaved (as had been advertised elsewhere). Clearly Sanctuary’s advice (and this experience) trumps those advertisements at least where UVs are concerned… and maybe even further since those two displays were present without even any material defined.

Anyway, its been great meeting you all and I appreciate all the help. Maybe now I can move on with the tutorial :wink:

The other person that I met - so to speak - while working on modeling the “backbone of the shipping industry” was a re-invented character (Flo - “kiss my grits”) from a 1970’s sitcom portrayed by the actress Polly Holiday :slight_smile:


Happy to help.

Something worth pointing out with this, is you have all the key vertices placed. Using the snap tool (snapping to vertices) while locking axes will get them where you want. Even on a remodel, you can still leverage a lot of existing work so long as it’s in the ball park of what you want!

Just another random thought, it’s also a bit of a tough object due to the inside. Modelling the inside might be easier then use the Solidify modifier, making future adjustments then can be simplified.

Lol, nice!

P.S. you might like these:

Uhm, there are some parts where the mesh looks messy. For example, on the top, what are those weird faces? If I’m not mistaken it should be flat there. I’d fix that. :slight_smile: I think it’d help in having a nice UV unwrap. I’d expect a squar-y wireframe there.

See what I mean:

Thanks Quantum for the suggestion of working from the complex to the simple and from the inside outward. For the other three corner fittings (top left, top right and bottom right) your other suggestion to simply remodel from this model (bottom left) will probably be put to immediate use after this current exploration into textures.

Seeding A New Thread - ? (who knows when / where)
Thanks also for the blendswap.com link; I’ve not seen the site until this morning. I am glad to see that some semblance of the spirit that brings an open source project to fruition can be seen in its users’ fruits. Have you ever shared your blends there? Have you ever used any of the site’s shared blends?

Aye, check the “Downloads” link in my signature, it will take you to Blendswap and filter for my models. I used to have more up but removed them for maintenance. They weren’t much worth fixing to put back up, so I never did. I’ve come to find my passion is making Creative Commons (CC) content.

I used to use them to study in fact, it is very helpful to see how others approach modelling decisions. Examples of both right and wrong are very educational. Even beyond that, I have in various projects to fill scene environments and will be trying to make extensive use again very soon for the Bot Siege project : http://blenderartists.org/forum/showthread.php?273336 When making stills or animations and posting to this site finished projects, however, I don’t use any external assets, it’s all from scratch.

Thanks Kolossus - is this more what you had in mind:


Snip from test no. 12-002 (probably one too many subsurf divisions :wink:

Very nice work Quandtum! and props to you for sharing. Your Gallery is also very good, particularly well done are the two nude studies, excellent! Did you model these with Blender?

No, that’s free stuff from DAZ 3D. Initially it was going to just be an asset stand in for various visualization projects, but then I used it to focus study material settings (I don’t need to worry about mesh, UV’s and textures then, just material and lighting). I learned the gritty details of my render engines, I had to learn what most all the settings did to get stuff to work (and with multiple renderers). Then I explored making conforming clothes to sell and try to earn some money, but I didn’t find it worth the effort. Now, it’s just something I occasionally poke in between projects for something small and quick.

I would consider cleaning some of it out of my gallery, but since it’s already there and some people like it, I leave it. I admit, I’m embarrassed with some of it, so perhaps it is a reminder to myself to be more diligent and convey more purpose in what I render. I have in the past done my own various bodies and heads (many of which I have cleaned out of the gallery, they were some of my first projects). Now I prefer more low-poly projects.