AssetPostprocessor.OnPreprocessAsset()

Description

Add this function to a subclass to get a notification just before any Asset is imported.

This lets you control the import settings through code.

Unlike other `OnPreprocess` callbacks such as OnPreprocessTexture or OnPreprocessModel, `OnPreprocessAsset` does not automatically register a dependency on the postprocessor. This means that if your subclass only implements `OnPreprocessAsset`, changing the value returned by GetVersion does not trigger a reimport of affected assets. To register dependencies explicitly, use AssetImportContext.DependsOnCustomDependency or AssetImportContext.DependsOnArtifact through the context property.

Note: If your subclass also implements another callback such as OnPreprocessTexture, the dependency is registered by that callback and GetVersion works as expected.

using UnityEditor;

class PresetEnforcer : AssetPostprocessor
{
    void OnPreprocessAsset()
    {
        if (assetImporter.importSettingsMissing)
        {
            ModelImporter modelImporter = assetImporter as ModelImporter;
            if (modelImporter != null)
            {
                if (!assetPath.Contains("@"))
                    modelImporter.importAnimation = false;
                modelImporter.materialImportMode = ModelImporterMaterialImportMode.None;
            }
        }
    }
}

using UnityEditor;
using UnityEngine;

//The following example registers an explicit custom dependency so that changing the dependency hash triggers a reimport of affected assets.

class PresetByFolderPostprocessor : AssetPostprocessor
{
    static readonly uint k_Version = 1;
    public override uint GetVersion() { return k_Version; }

    [InitializeOnLoadMethod]
    static void RegisterDependency()
    {
        AssetDatabase.RegisterCustomDependency(
            "PresetByFolderPostprocessor",
            Hash128.Compute(k_Version.ToString()));
    }

    void OnPreprocessAsset()
    {
        context.DependsOnCustomDependency("PresetByFolderPostprocessor");

        if (assetImporter.importSettingsMissing)
        {
            // Apply default import settings based on folder location.
        }
    }
}