I’m trying to find a faster way of straightening the UV layout of the mesh below to make it more efficient for packing.
My first attempt involved manually selecting the inner UV vertices, aligning them in a straight line, pinning them, and then unwrapping. The result:
It was pretty time consuming. I was wondering if there’s a more effective way of doing this since I’ll be dealing with a lot of these kinds of shapes.
Off the top of my head: it appears to have several possible axes of symmetry. Why not just fold it along one of those? Takes up far less space, and doesn’t require doing weird things to mapping. You could even cut it into quarters.
Alternatively, if you think that will bork something, since the inner ring is defined by mesh anyway you should be able to pack other items inside it. Is straightening it really necessary?
Good point. I might use the approach you mentioned.
There are some cases though where I might want to add text or small details aligned along the circumference of the inner circle. This can be done by using a stencil or exporting the UV layout into a texturing app. It will be a lot easier to add these details if the UVs were straight.
Photoshop will do text along a path, and I bet GIMP will too. This makes it easy to put text around a circle. You just define the path first, then type normally.
Works with shape brushes, too. Rings of rivets around a path is easy when you know how.
I totally agree that Photoshop can do text along a path.
But then the question of how to straighten the circular UV island more effectively is left unanswered. I guess I’ll try experimenting with custom scripts.
A brilliant mind called Zaloopok has a nifty tool called Line Up / Equalize, which lines up vertices and edges on a straight line. Equalize spaces vertices evenly while Line Up preserves relative vertex distance.
You can get it from the bottom of the page of this link.
(the file itself is called zaloopok-0.6.20170206.zip)
https://sourceforge.net/p/blenderbitsbobs/wiki/Zaloopok/
When installed, you’ll find it in the Misc tab of the T-panel.
I love this tool.
Wow. Just tried the tool. Works perfectly. Thanks!
That’s genius. I can see some uses for that in my own stuff. Grabbing now. 
Although it does necessarily involve considerable distortion of mapping, so would have to be used with caution. But still, very useful in the right cases.
Related to this thread I have been working for a while now on an upcomming tool for TexTools called “Pin & Relax”
It unfolds and Pins selected edge loops into straight lines and relaxes the rest of the UV island. Similar to Headus UV layout with its edge constraints. Unlike the previous examples here it does not re-scale the edge distance but instead maintains it.
There is also support for selected multiple edge loop sets where it straightens and relaxes them largest to smallest but this mode is not yet fully fool proof.
