Simply speaking Pre-Rotation… well, rotates all islands to an orientation which is likely to be most optimal for the packing purposes. You can do a simple test:
Create a single UV island which is a perfect square (you can use the default cube to do it easily)
Now rotate this island of about 45 degrees (so the square edges are not aligned with X and Y axes)
Make sure all UVP options are reset to default.
Select the UV square and press Pack - note the result you get.
Undo the last pack operation (so the square is not aligned again)
Now check “Pre-Rotation Disable” option and press Pack again.
Compare results
Conclusion: do not check the “Pre-Rotation Disable” option unless you really need it
So, I assume your problem is solved now, or you need some more help?
Hi, @glukoz I have a problem with UVPackmaster. Blender just updated to 2.93, and version 2.5.0 wont work anymore. I downloaded a free UVP engine version, and a new version of addon. But thing is, UVP engine version is 2.5.7, and the addon version is 2.5.6. So when im trying to select a path of UVP engine, blender says “UVP initialization failed: Engine version 2.5.6 required”. Also, in 2.5.0 version in UVP engine folder, i have a “release” thing, but in 2.5.7 version there s different folders and i cant find a similar file at all. I also tryed to select 2.5.0 UVP engine version, but i m getting same message. Please help
Note that version 2.5.0 is obsoleted and it won’t work with Blender 2.93. You just need to use the latest version of the packer: 2.5.6.
I just wonder where you found engine version 2.5.7 - there is no such version of the engine You just need to download the engine version 2.5.6 from Gumroad or Blender Market (depending on where you purchased the packer) and install it in the usual way, as described here.
P.S. Note that there is a free SDK version 2.5.7, but SDK is a different thing - it is not the engine. You should pay attention to product names on Gumroad
Oh…and so it does, nothing happened when I installed it (the option to turn it on etc) however I found it at the bottom of the list…excellent!!!
Tankyou!
That’s correct: if one wants to try UVPackmaster with Blender 3.0 he or she has to use the latest packer version 2.5.6, though Blender 3.0 is not officially supported yet (we usually start supporting a particular Blender version after it is released as beta).
One of the features of the upcoming packer major releases will be a complete UI rework. So who can give us better ideas for how we should redesign the UI than you: the users?
That’s the reason why I would like to ask you for feedback regarding the packer UI in Blender: what works well for you in the current UI? What would you change and how would you change it? The more details you give, the better.
Also, if you have an idea for a new packer functionality, mode of operation, it is a good moment to share it with us.
Users who send us the most valuable feedback will be kindly asked to participate in beta tests of the upcoming major release. Yes - the general scope of changes in the packer architecture is going to be so wide that it will require some beta testing. And I can’t wait for the moment when I can share more details about changes to come
Guys, when a dev is as hard-working and dedicated as glukoz, and especially when their product is this damn good, we as users/customers should really make an effort to reward that hard work and dedication. I personally am going to try to evangelize UVPackmaster with my limited free time, similar to my spreading of the good word for B-Renderon and E-Cycles. When I like something a lot, I definitely let others know about it, when I can. I encourage you guys to do the same for glukoz. He has certainly earned it at this point! And not just here on blenderartists or game dev related sites… Every single person who uses blender and exports glTF/glb for WebGL should absolutely have UVPM! Next time I am on threejs forums I will try to spread the gospel there… Come on guys, lets get glukoz some more sales (even if he isn’t hurting for it)!
Hi! Love this packer, just wanted to say I found an instance where the packer fails to do a decent packing, maybe there’s some option I don’t know, and of course there are workarounds.
This is a simple example but the problem persist with lots of islands if the 4 circles are the biggest islands. I let it iterate and didn’t get better.
It’s not a serious problem but I wonder if it could be fixed.
It seems packing by bounding box is useful sometimes hahaha Thanks for the addon!
Yes, there might be rare cases where the bounding box approach would be better. Note that in your example the way to go strictly depends on the number of circles you want to pack: for 4 circles the bounding box approach is better indeed (as you have shown), but if only you were about to pack for example 2 or 5 circles, then UVP would produce a better result.
As you can see it is generally hard to tune an algorithm to produce the optimal result for every kind of input, so I simply focus on creating the algorithm which gives the optimal result in 99% of cases Other 1% of cases are quite specific and easy distinguishable so one can just use the Blender native algorithm when he encounters them.
RELEASE 2.5.8 (UVPackmaster for Blender and UVPackmaster SDK - both components were updated with the same fixes and have the same version number now)
fix a bug in the Fixed Scale mode, when sometimes packing was stopped even if there still were islands which would fit into the packing area (this bug was recently reported by a user and fixed immediately. Remember if you believe you found a bug in UVPackmaster, do not hesitate to report it to [email protected]).
You just need to download the engine version 2.5.6 from Gumroad or Blender Market (depending on where you purchased the packer) and install it in the usual way, as described 
Other 1% of cases are quite specific and easy distinguishable so one can just use the Blender native algorithm when he encounters them.