To prevent the regeneration of material assets in Unity when using Spine, you can implement a custom AssetPostprocessor to handle the assets as needed. This approach allows you to control the behavior of asset processing and avoid the automatic generation of new materials if they already exist.

Here's a basic example of how you can create a custom AssetPostprocessor:

using UnityEditor;
using UnityEngine;

public class CustomSpineAssetPostprocessor : AssetPostprocessor
{
    static void OnPostprocessAllAssets(string[] importedAssets, string[] deletedAssets, string[] movedAssets, string[] movedFromAssetPaths)
    {
        foreach (string asset in importedAssets)
        {
            if (asset.EndsWith(".mat"))
            {
                // Check if the material already exists in the desired folder
                string targetPath = "Assets/YourTargetFolder/" + System.IO.Path.GetFileName(asset);
                if (System.IO.File.Exists(targetPath))
                {
                    // If the material exists, move it to the desired folder
                    AssetDatabase.MoveAsset(asset, targetPath);
                }
                else
                {
                    // If the material does not exist, you can handle it accordingly
                    // For example, you can delete the newly generated material
                    AssetDatabase.DeleteAsset(asset);
                }
            }
        }
    }
}

In this script:

• The OnPostprocessAllAssets method is overridden to handle the post-processing of assets.
• It checks if the imported asset is a material (.mat file).
• If the material already exists in the target folder, it moves the new material to the desired folder.
• If the material does not exist, it deletes the newly generated material to prevent duplication.

This way, you can ensure that materials are not regenerated unnecessarily and are organized according to your project's structure.

For more detailed control, you can expand this script to handle other asset types like textures and animator controllers similarly.

belovedquestioningly When I follow a similar format, a second user, on a different machine gets new material assets generated because of the assetpostprocessor. Is there any way to stop this regeneration if an existing material exists?

While the description by Spinebot is valid, this should not be necessary at all.

Are you sure that the assets have been added to version control? If the Materials already exist or settings have been modified, they will not be overwritten.

Which exact version of the spine-unity runtime are you using (name of the unitypackage, also listed in Assets/Spine/version.txt, or version listed in the Unity Package Manager)?

belovedquestioningly Is there anything I need to set in the Spine Preferences within the Preferences?

No.

My previous question remains:

Are you sure that the assets have been added to version control? If the Materials already exist or settings have been modified, they will not be overwritten.

@belovedquestioningly Thanks for the info, this is strange then. Could you perhaps share some screenshots or even better a short video showing how new materials are generated?

Alternatively, if you can create a minimal Unity reproduction project with a description of reproduction steps which make this issue occur? You can send it as a zip package to contact@esotericsoftware.com, briefly mentioning this forum thread URL so that we know the context.

@belovedquestioningly We have just released a fix for the issue on the 4.2 branch, moved Materials should now be recognized upon (re-) import and no longer deleted and re-created.

A new spine-unity 4.2 unitypackage is available for download:
https://esotericsoftware.com/spine-unity-download
Please let us know if this resolves the issue on your end as well. Thanks for reporting!

@belovedquestioningly Unfortunately I could not reproduce this issue. The steps I've taken are:
1) imported your MaterialsControllersIssue.unitypackage, let the materials and assets be generated.
2) add the top-directory of the assets to git.
3) deleted the directory locally, switch to Unity to let it update it's DB.
4) restored the directory to it's previous state again via git checkout .
5) switched to Unity to let it import the assets once more.
6) observe that git status shows no changes after the same assets were imported a second time.

What are the changes you see, can you share a diff? In general please always describe everything with as much info as possible.

belovedquestioningly Submit the assets to a server;

Please always describe any steps as precisely as possible. "the assets" is very vague, did you add all assets of the folder to version control? "submit to a server" is very vague as well. What version control software you're using, how did you submit the assets?

I have to repeat the question of my previous posting, since you haven't answered it:

Harald What are the changes you see, can you share a diff? In general please always describe everything with as much info as possible.

belovedquestioningly Can you describe what "What are the changes you see, can you share a diff?". Would you like to see the diff for these three files?

Yes. It would be interesting to see a diff of the files that you find problematic that they changed. You posted the following text earlier:

Which when connected to a version system, (we used P4V), it marks the files _Atlas.asset and _Material.mat as modified even though there are no visible changes. Is there a way to avoid this? Thanks.

Since there are no "visible changes" that you see, it is necessary to see a diff of these files.

belovedquestioningly Thanks for the additional info. Then it's highly likely that you've configured your version control system to always checkout files with a different line ending (e.g. lf instead of crlf) than the one that Unity produces when writing asset files on your machine. So when you checkout your files, you receive one line ending and when Unity just touches the file it's of a different line ending. You thus need to make sure both line ending styles match to avoid undesired diffs.