Cache Server FAQ

Will the size of my Cache Server database grow indefinitely as more and more resources get imported and stored?

The Cache Server removes assets that have not been used for a period of time automatically (of course if those assets are needed again, they will be re-created during next usage).

What changes will cause the imported file to get regenerated?

When Unity is about to import an asset, it generates an MD5 hash of all source data.

For a texture this consists of: - The source asset: "myTexture.psd" file - The meta file: "myTexture.psd.meta" (Stores all importer settings) - The internal version number of the texture importer - A hash of version numbers of all AssetPostprocessors?

If that hash is different from what's stored on the Cache Server, the asset will be reimported, otherwise, the cached version will be downloaded.

How do I work with Asset dependencies?

The Cache Server does not handle dependencies. Unity's asset pipeline does not deal with the concept of dependencies. It is built in such a way as to avoid dependencies between assets. AssetPostprocessors are a common technique used to customize the Asset importer to fit your needs. For example, you might want to add MeshColliders to some GameObjects in an fbx file based on their name or tag.

It is also easy to use AssetPostprocessors to introduce dependencies. For example you might use data from a text file next to the asset to add additional components to the imported game objects. This is not supported in the Cache Server. If you want to use the Cache Server, you will have to remove dependency on other assets in the project folder. Since the Cache Server doesn't know anything about the dependency in your postprocessor, it will not know that anything has changed thus use an old cached version of the asset.

In practice there are plenty of ways you can do asset postprocessing to work well with the cache server. You can use:

Working with materials

Modifying materials that already exist might cause trouble as well. When using the Cache Server, Unity validates that the references to materials are maintained. But since no postprocessing calls will be invoked, the contents of the material can not be changed when a model is imported through the Cache Server. Thus you might get different results when importing with or without Cache Server. It is best to never modify materials that already exist on disk.