Bug Unity made full project reimport on every small change

Just updated to Unity 2020 and already have reimported project about 5 times because every project chnage fires project reimport (all textures and meshes got reimported)

- Update Unity - got reimport
- Update URP - got reimport
- Update TextMesh Pro package - got reimport
- Added Backery to Project - got reimport
- Updated Android logcat package - got reimport

This is very bad workflow of new Unity. Is it known? When UT plan to fix this?

 

And it looks like Unity AssetDatabase v2 dont work actually because All textures absolutely dont change by any of changes but fully reimported and dont get from already imported AssetDatabase.

 

case 1317873

 

https://forum.unity.com/threads/upd...ire-project-to-reimport.1072157/#post-6985475
https://forum.unity.com/threads/why...eimport-of-all-textures.1065839/#post-6884252
Seems even TextMeshPro dev dont know why.....
There's no meta file changed after reimport. And for example delete Bakery or remove ProBuilder also trigger reimport.
So I guess this is a bug. The same point maybe we all upgrate project from old version. I upgrade from 2017.4 to 2020.2.
Can I konw which code maybe trigger reimport? Maybe I can search code to see where triggered.

 

Last time I changed packages it was 2020.2.6f1
You can see this in bug report

 

And reimported prefabs is not a problem for me they all took about 2 minutes
Issue is reimported textures

 

I submit 1329863.
In my work project 2020.2.5 update TextMeshPro also trigger reimport but in this project not reproduced.

————————————————————
Addition test PloyBrush also trigger

 

Ok, I konw what you mean. If there's a new OnPreprocessTexture, all texture should excute this OnPreprocessTexture.
But IconImporter only process ProBuilder's textures, other texture settings in this project are not modified, they should not do addition compress or any other operators even download from cacheserver.

 

It will be good to also have fast reimport of textures, like if preprocessors change nothing to texture than do nothing and go to next texture

 

@volblob73 this behavior has been changed recently, since Unity 2020 something? I don't recall Unity doing this in earlier versions. It used to require triggering a manual reimport to update the asset settings, even with custom asset processors in place. This was a much more preferable workflow than getting hit by random and completely unnecessary reimports! There should at least be an option in the preferences that can be turned off again... It might not be an issue if you work on empty projects, but in the real-world this is incredibly frustrating and a complete waste of time.

 

@volblob73 Thanks for your answer! I already have auto-refresh disabled, but it doesn't stop Unity from starting reimports of the entire project now and then, when some code gets recompiled, unrelated to any package changes. I assumed it was triggered by a preprocessor, but after checking the files, none of the changes were actually applied during the re-import. Only when I manually re-import the assets it will update the settings, which is how it used to be all along. I'll move my frustration to another thread/bug then.

 

Yeah, this really looks like a bug IMHO.
People have huge projects with multiple hours worth reimporting time. I always thought that asset postprocessors are only called if WHEN the reimport is triggered, but they don't trigger the reimport itself.
Now I have reviews like this




It didn't even get to my code - simply blocked the user during package import.

I also don't remember it happening pre-2020 TBH. Simply creating an asset postprocessor script in the project definitely didn't force project reimport.

 

So I decided to check which Unity versions actually reimport the entire project worth of textures when you simply create a script with OnPreprocessTexture:

5.6: nope.
2017.4: nope.
2018.3.3: nope.
2019.3.4: nope.
2020.1.2: nope.
2020.1.14: nope.
2020.2.2: yes.
2020.2.7: yes.
2020.3.2: yes.
2021.1.7: yes.

So it looks like a bug/regression that was added somewhere between > 2020.1.14 and <= 2020.2.2.

 

Hmm, all previously written scripts were still written assuming old behaviour (e.g. I only care about the new lightmaps being imported after the asset is installed). Perhaps there should be some specific [ReimportAll] tag explicitly set in the script to force the new behaviour? This way both behaviours are possible. But currently old behaviour just suddenly costs a few hours (sometimes days) of reimporting.

If some scripts actually wanted to re-process all project assets and it wasn't reliable, it seems like a wrong way to solve it. E.g. it could be solved by making the script detect that it was just installed and optionally iterating over all (or not all) assets and reimporting them, then setting some flag somewhere to not repeat it.

Finally, judging by its name and the docs, OnPreprocessTexture is just a function that "gets a notification just before the texture importer is run". It's a callback, and from the API user perspective it's totally not predictable that it can actually cause some action (not react on action).

 

Is there a hacky way to avoid this project-wide reimport? I mean, is there some sort of "all textures must be reimported" flag somewhere in Library/Temp/etc. that I can manually set to false ( ͡° ͜ʖ ͡°)

 

We are working on a huge project with a lot of high quality 3d models and textures, having more than 500 GB in the Library folder alone - and with each single changing of anything, including some small scripts that have definitely nothing to do with the here mentioned processes, Unity starts to reimport all.

Wasting days because of this bug - and it defintitely IS a bug and not normal behavior. I can confirm what guycalledfrank said: This big problems did not exist for older Unity versions, they also had a lot of issues, but definitely not a reimport after each super small and simple script changing.

Please Unity team focus on improving editor behavior and HDRP performance. You have been losing massively in competitiveness to Unreal for a few years now, because larger projects with higher graphics demands are practically almost impossible to implement. And we really don't want to have to switch. Thank you.

 

I can't say that ANY script change triggers a reimport for me, BUT the fact that changing an AssetPostProcessor script simply triggers a reimport of the whole project is not sensible at all. When i am iterating i need to make changes often and it is completely sufficient for me, to just test with the reimport of a single asset to see if my code works as expected.
I mean just make a PopUp telling the user: "Hey your Asset Processors have changed do you want to reimport the project" - "Yes" , "Hell No!" . It can't be that hard, i know the people at Unity are incredibly smart people.

For all you having issues with texture reimports, have you tried setting the editor preference of Compress Assets on Import to false ? I am currently working on a MeshPostProcessor and so i am not sure if this helps in your case but it was very helpful to a lot of my colleagues who only need the texture to compress when actually building. I can also recommend switching to PC Standalone because from my experience DXT compresses A LOT faster than ASTC/ETC2 even though performance has improved significantly from 2019 to 2021. Asset Cache Server would also help a ton but only really works if you're on the same local network or everyone has amazing internet in their home office

Also with 2021 you can see which Processors are active when you check the import settings of a Texture or Mesh, that might help pin down the a simple script triggers reimport. Maybe the script is part of an assembly def that contains a Processor ?

 

Just for the record: For some reason the issue disappeared again and updating the post processor script no longer triggers a complete reimport. I think there might be a weird bug or something.

But nevertheless Unity should always give developer the option to postpone a reimport of the whole project - because this is something that Unity is really infamous for and has become a meme at this point.

 

Bump.
Please put this information on the AssetPostprocessor.OnPreprocessTexture() documentation page. Finding out that the function will reimport every single texture in the project only after implementing it is very detrimental, and so easily avoidable.

 

This is frustrating. Please let user have a button to Yes / No this whole project reimport. Some asset store asset triggers this on install.
Polybrush, Animancer Lite, Archimatix. Those are just the one I know, might be much more.

 

has the issue been fixed?

 

... another clear indication that from Unity 2017.4 (stable) versions - the community is derailed from the track, from what Unity was and should be: reliable and productive. Also, these new 'admin' nag features and impossible to follow 'restrictions' of what the user can do: should stop, asap and such violent level of restrictions be removed. We should not have allow any further this technocracy violence (from where ever and what ever excuse is coming from). And since the versions 2017 - it's not Unity any more, and it's too obvious by now, not related only to the problem discussed above. So it all should be reverted back to 2017's free-use - open functionality policy (open and free, and productive) functionality, for at least one point of what can be helpful. Unity also needs to learn not to complicate, and not to implement from technocracy reasons what is not Unity, and never will be. Such issues happen every time when the community is not consulted, and is derailed as currently, as to where the Unity direction should be next, as well.

 

I can definitely confirm - removing or adding Pro-Builder will also lead to a reimport of the whole projects - which can take a very long time. In my opinion there needs to always be a question for the user if a full-reimport should happen or not

 

... it's not only the OnPreprocessTexture case that is causing the complete project re-imports ... every legit build is causing it as well, soon as you hit the 'build' button ... Same as a the range of other conditions, even the slightest code changes, at the times. This, with the Unity's circa 2020'es up - is a serious bug, and a mistake of how the admin features and non-necessary resrtictiveness are added, and that should not be there, at the first place. As they don't provide any better quality, only a colossal loss of time. And that can not be called 'new' or a 'new quality', sorry, but nope, for our vote on the subject. It is a multi-cluster nature bug, that needs to be ironed out, and that will persist, untill the day it gets removed .

 

I have problem too. After build, reimporting long time... crash Unity, destroy my graphic driver. Unconnect my second monitor and get do some default windows driver. After updating Unity to never version 2021.3.20f1. After build crash with the same result plus destroy driver completly to black screen. Now ist better.... remove all AssetDatabase.Refresh() from codes, remove baking light.... build is done. Reimporting is still long( 2 min ). I dont know, but my build now show only GUI and all 3D object and skybox missing. Aaaaa....

 

Another day lost here to this problem. 2020.3.39f1. It takes like 3 or 4 hours to reimport my project due to its size.
How about asking for reimport first? A yes/no window would be great.
I am importing Amplify Impostors from the Asset Store. Other assets also triggered this but I don't remember what they were.

Also minor versions updates of the engine can cause the reimport sometimes. I use Unity since 3.x, this was not happenning years ago with Unity 2018 at least.

 

Unity, your laziness and or focus on new features instead of fixing existing one's is causing people to waste an inordinate amount of time. I've had textures get re-imported many times for no valid reason, and because of the project size I've got to wait a day each time. For the love of god just put in a popup that says something like "You've just updated Clang for NX, do you wish to import all textures? This will take approximately 24 hours", with 2 buttons that say "Yes" and "F*** no". I've been in the gaming industry for 23 years and working with Unity is by far the worst experience I've ever had. I'm sure it's fine for little projects, but for anything serious it just wants to make you tear your hair out every day.

 

Workaround time!

I think I've found a way to make it work at least for asset developers.

So currently, if you have:

void OnPreprocessTexture()

in your script, Unity goes crazy and starts reimporting all textures in the project.

However, there is a less known method, called OnPreprocessAsset: https://docs.unity3d.com/ScriptReference/AssetPostprocessor.OnPreprocessAsset.html

It's called for every asset, but we only care about textures, so we can just cast and check:

TextureImporter importer = assetImporter as TextureImporter;

if (importer == null) return;

OnPreprocessAsset does NOT force full project reimport!
That would be a happy ending, if only REMOVING OnPreprocessTexture from an existing script wouldn't force the full project reimport again!

Unity actually seems to store a hash of all applied preprocessor script IDs on every asset. If the hash doesn't match (added/removed a preprocessor), the reimport is forced.
Thus, the true solution (that doesn't break new projects AND existing ones) looks like this:



This way:
- OnPreprocessTexture works as usual on older versions (OnPreprocessAsset didn't exist before 2018.1)
- OnPreprocessTexture is still used in an existing project, thus not invalidating the preprocessor hash and not triggering full reimport when upgrading.
- OnPreprocessAsset is used when importing to a new project, not triggering full reimport.

Full preprocessor code snippet, as used in Bakery:

Code (CSharp):

1. #if (!UNITY_2020_2_OR_NEWER)
2.     // Pre-broken Unity
3.     void OnPreprocessTexture()
4. #else
5.     // Do not use OnPreprocessTexture on >= 2020.2.2 due to it forcing full project reimport!
6.     // https://forum.unity.com/threads/unity-made-full-project-reimport-on-every-small-change.1066844/
7.     #if (!BAKERY_INCLUDED || BAKERY_NOREIMPORT)
8.         // First package import OR the new define is set
9.         void OnPreprocessAsset()
10.     #else
11.         // Existing project - don't change the method, or the preprocessor hash (?) will change and trigger the full reimport again!
12.         void OnPreprocessTexture()
13.     #endif
14. #endif
15.     {
16.         TextureImporter importer = assetImporter as TextureImporter;
17.         if (importer == null) return;

Note that "BAKERY_INCLUDED" is a define that Bakery already added when being imported to a project. If your asset doesn't add something like this, you'll need a different way checking for its existence.

The define adding code:

Code (CSharp):

1. using UnityEngine;
2. using UnityEditor;
3. using System;
4. using UnityEditor.Build;
5.  
6. [InitializeOnLoad]
7. #if UNITY_2017_4_OR_NEWER
8. public class ftDefine : IActiveBuildTargetChanged
9. #else
10. public class ftDefine
11. #endif
12. {
13.     static void AddDefine()
14.     {
15.         var platform = EditorUserBuildSettings.selectedBuildTargetGroup;
16.         var defines = PlayerSettings.GetScriptingDefineSymbolsForGroup(platform);
17.         if (!defines.Contains("BAKERY_INCLUDED"))
18.         {
19.             if (defines.Length > 0) defines += ";";
20.             defines += "BAKERY_INCLUDED";
21.             if (!defines.Contains("BAKERY_NOREIMPORT"))
22.             {
23.                 defines += ";BAKERY_NOREIMPORT";
24.             }
25.             PlayerSettings.SetScriptingDefineSymbolsForGroup(platform, defines);
26.         }
27.     }
28.  
29.     static ftDefine()
30.     {
31.         AddDefine();
32.     }
33.  
34. #if UNITY_2017_4_OR_NEWER
35.     public int callbackOrder { get { return 0; } }
36.     public void OnActiveBuildTargetChanged(BuildTarget previousTarget, BuildTarget newTarget)
37.     {
38.         AddDefine();
39.     }
40. #endif
41. }

Note that it adds both the original BAKERY_INCLUDED, and the new BAKERY_NOREIMPORT, which is only added if BAKERY_INCLUDED wasn't previously set.

Hope this helps someone!
I'd like to push the update to the store soon.

 

Alright, so I took the day off from my day job to do as much work as possible on my project that we want to release very soon.

Made myself a coffee, fired up the computer, and saw that from a computer to another, my packages-lock file was different. So on the one that had older versions of the packages, I went and started to update them.

Note: project is source controlled and the packages are supposed to be the same on every machine but somehow the packages-lock files want to be different.

There goes my f#$%?& day. Now it's reimporting everything.

This is so frustrating, you have no idea!

 

If you are at a point in development where making builds isn't super common (you don't need to do builds daily or weekly or something), disabling "compress Textures on import" in Unity's settings can make these reimports take ~15 minutes (more or less depending on project size and computer used) instead of several hours, which still kinda sucks when it happens but it's not "I lost the whole day" levels of delay.

 

Depending on the project size, you can go out of memory if you disable it...

 

Fair point.

 

imagine waiting 8 hours for project re import, because probuilder need to process 3 icons.
Graz Unity, not fixing critical bug for more than half year.

 

We switched to the new Unity versions; their editor works much faster. They really did something wrong in the 2020 and 2021 Unity versions; they are so laggy. In 2019 everything was working perfectly and fast, and in 2020 and 2021, it started to take 10 times more time for everything. We were upgrading to the latest versions as they came out, and I can tell that 2022 is much faster than 2020 and 2021. And 2023 is even faster, but of course, it's still Beta.

I'm not sure if they would be able to fix it in general. Maybe just switching to a new version would help, if it's an option. At least that's what helped us to save a lot of time. Now my project opens in 1-2 minutes in the latest versions of Unity. In 2021 and 2020, it was taking 30 minutes just to open (and it was not re-import, it just how much time Unity is taking JUST TO OPEN a project). Ridiculous.

 

@aras-p Is there any advancement on a feature that would allow to allow/disallow a full project reimport.
I mean there is already the safe mode for when you load a not compiling project, sure there is a way to trigger safe mode whenever a reimport would be needed ?

This is terribly annoying, and I measure my words, any advanced asset, first Mesh Combine Studio now Easy Decals, they all trigger a reimport that take hours. This can't be happening.

Wake up, there are only 300 days or so in a year. 7 in a week. you can't block users for days like this. Look at all the frustration people have. I'm pretty sure you even face the issue internally on your own projects and experiments.

@guycalledfrank Thanks to your finding, would there be a way the check for missing / added preprocessors ids and by pass the regular reimport before it's too late ?

 

Okay, so I've been using this workaround, it worked twice, when you identify a full reimport (depending on your project I believe) just kill Unity and launch it again.
Last time I imported Mesh Combine studio it hanged for 3h, I was fed up I killed it, on next launch no reimport.
Just did the same with Easy Decals at the moment we speak.
Unity 2021.3.18.

Doing so it broke some assets so just be sure to version whatever needs to be, then I reimported 1 by 1 each broken assets, which took 10 minutes not hours ...

 

I have left Unity two years ago, so no idea on that front!

 

I have experienced, that safe mode also triggers the full reimport as it blocks custom preprocessor scripts from compiling, thus possibly modifiing the hash @guycalledfrank mentioned (although I did not found any info or changes on the files, so it must be stored somewhere internaly)

 

Somewhere in the Library folder or in the asset database cache ?

Your project reimports while in safe mode as well ? That would be a bug in my sens as it is specifically advertising as to avoid reimports on broken scripts.

 

Thanks for your answer, would you know who we can ping on that ?

 

Well I don't know if there is any database of added postprocessors, I just use a simple global define check to avoid declaring the triggering method, as you can see.

 

Third time is a charm, can confirm the workaround on a new asset import.