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Often when I am modeling something I need to add some very fine detail to certain areas of the mesh so I add some very tight loop cuts in that area. However when I go to unwrap it, even if it is very simple square geometry Blender will severely warp the pelt.

For example, if I have a simple cube and unwrap it it looks fine:
enter image description here

But if I add a few very close loop cuts the pelt is horribly distorted:
enter image description here

Here is another example:
enter image description here

In both these cases the geometry is very simple and box-like, all quads. But it becomes distorted when I unwrap it and I have to waste time manually aligning all the edges in the UV editor. This also sometimes happens when I have many proximity cuts for use with a subsurf modifier.

Why does Blender do this and is there a way of preventing/fixing it?

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    $\begingroup$ Do you have the same behaviour with "conformal" Unwrap method? $\endgroup$
    – Carlo
    Aug 6, 2015 at 15:57
  • $\begingroup$ @Carlo No, that fixed it, thanks! If you put that in an answer I'll accept it. $\endgroup$
    – PGmath
    Aug 6, 2015 at 16:00
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    $\begingroup$ Thanks but maybe is better to leave it open hoping someone with more knowledge can tell the difference between the two methods. I didn't write answer beacuse I can't tell you WHY it happens. Even this related answer doesn't go in depth: blender.stackexchange.com/questions/238/…. It would be interesting to know more about it! $\endgroup$
    – Carlo
    Aug 6, 2015 at 16:11
  • $\begingroup$ @Carlo, you might as well put that much as an answer here, I have asked a new question about the technical differences between the two. $\endgroup$
    – PGmath
    Nov 5, 2015 at 18:20

2 Answers 2

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As mentioned in the comments, Blender supports two algorithms for making a 2d projection of the mesh, Angle Based and Conformal. Angle based is the default and generally handle complex and organic shapes better, but runs into problems for some cases (e.g. the tight loop cuts you are using). In these cases it is best to try the Conformal algorithm.

The conformal term comes from the mathematical term conformal map, a function/projection that aims to minimise the difference in angles between the source and destination. More details on the particular method used can be found here if you are mathematically inclined.

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If you make your loop cuts without the mesh selected (and showing the UV layout), then select all to see the UV layout again, it seems to work properly that way.

enter image description here

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    $\begingroup$ The problem is most of the time it's not practical to unwrap and then finish modeling. Things like scaling (try doing this operation with a UV grid) and extruding will distort the UVs. I actually already fixed the problem by using conformal unwrapping. $\endgroup$
    – PGmath
    Aug 6, 2015 at 16:42

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