AssetPostprocessor reference to asset being processed?

Questions & Answers
1

I wrote this class to streamline import settings on a bunch of UI textures. In addition to setting import settings, I want to create a material for each texture. This works great if I use “Reimport” from Unity after the textures have been imported, but upon the first automatic import, the material’s texture is never set. It’s as if:

(Texture2D)AssetDatabase.LoadAssetAtPath(assetPath,typeof(Texture2D));

returns null. Note that this is the only technique I could figure out in order to get a reference to the current asset being imported. It seems like there would be a built-in pointer to it, but I found nothing in the docs. Does anyone know why that would return null upon first import? Or if there is a better way to get a reference to the Texture2D that is being imported so I don’t have to look it up using LoadAssetAtPath() ?

[Edited the code to reflect the answer below.]


using UnityEngine;
using System.IO;
using System.Collections;
using UnityEditor;

public class UITextureImport : AssetPostprocessor
{
	void OnPreprocessTexture()
	{
		if (assetPath.Contains("Assets/Textures/UI/") && assetPath.Contains(".png"))
		{
			// Set specific properties for UI textures.
			TextureImporter textureImporter = (TextureImporter)assetImporter;
			textureImporter.textureType = TextureImporterType.Advanced;
			textureImporter.textureFormat = TextureImporterFormat.AutomaticTruecolor;
			textureImporter.mipmapEnabled = false;
			textureImporter.filterMode = FilterMode.Point;
			textureImporter.wrapMode = TextureWrapMode.Clamp;
		}
	}
	
	void OnPostprocessTexture(Texture2D texture)
	{
		if (assetPath.Contains("Assets/Textures/UI/") && assetPath.Contains(".png"))
		{
			// Create a matching material if one doesn't exist.
			string materialPath = assetPath.Replace("Assets/Textures/UI/","Assets/Materials/UI/");			
			materialPath = materialPath.Substring(0,assetPath.LastIndexOf("/") + 1);
			
			if (!Directory.Exists(materialPath))
			{
				Directory.CreateDirectory(materialPath);
			}
			
			materialPath += "/" + Path.GetFileNameWithoutExtension(assetPath) + ".mat";

			Material material = (Material)AssetDatabase.LoadAssetAtPath(materialPath,typeof(Material));

			if (material == null)
			{
				// Material doesn't exist, so create it now.
				material = new Material(Shader.Find("UnlitAlphaImage"));
				material.mainTexture = texture;
				AssetDatabase.CreateAsset(material, materialPath);
			}
			else
			{
				// Material exists, so only assign the new texture to it.
				material.mainTexture = texture;
			}
		}
	}
}
2

If it is the first time importing, it sounds reasonable that LoadAssetAtPath would not find it yet. Perhaps you could leave the importer settings in OnPreprocessTexture, but move the material creation part to OnPostprocessTexture, since you’ll be passed the Texture2D in question.