⚠️ [regression] Packing is broken again

Unity Engine
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1

Unity 6 no longer packs the islands in order from biggest to smallest and that makes packing efficiency MUCH worse.

Taking a scene that was set up in Unity 2021 to produce one 2048 densely packed lightmap and baking it with Unity 6 produces bad results.

Take a look at this comparison:

UNITY2021
UNITY20211920×1662 457 KB

UNITY6
UNITY61920×1662 360 KB

We have been through this before. Unity had the same issue back in 2017 and it was eventually fixed, why was it introduced again? → Packing continues to be horrible, please fix ⚠️ again in Unity 6 - #17 by AcidArrow

Here is the image I made back then in 2017 to explain the issue, it is the exact same thing again:

image
image1024×576 96.7 KB

PLEASE FIX, unfortunately this one seems harder to work around than the other lightmapping regression I found in Unity 6 so my options seem very limited.

1 Like
2

IN-93450

I’m open to suggestions for workarounds, since I can’t really think of anything.

Maybe moving scenes back to 2021, baking there, then moving lightmaps and lightingdata back to Unity 6? Doesn’t seem viable, but I’m not sure what other choice I have.

3

I did a test with moving a copy of the project back to 2021 just to bake, but unfortunately Unity crashes during the baking process.

It seems I have no workaround.

Please fix.

4

Backporting is not supported and can lead to loss of data, or crashes as in your case. If you really have to do it for testing purposes, you HAVE to delete all cached data before opening the project in the older editor version. This means deleting these folders: Library, Obj and Temp (if it exists). If you haven’t done so previously, it may be worth trying that to see if the crash then goes away.

5

I am aware.

Unfortunately I can’t think of anything else to force the packing to not be terrible.

It’s been a few more days, I still have no work around. Is anyone able to get densely packed lightmaps? If yes, how?