Bug Precompressed ASTC textures

I just noticed that Unity already has a native importer for astc textures (by this I mean textures that have already been encoded to ASTC format outside of unity and stored in a .astc file)

This seems to work fine for LDR compressed ASTC textures, the textures are assigned the format RGBA_ASTC8X8_UNorm

However, for HDR compressed astc textures, the textures get still assigned RGBA_ASTC8X8_UNorm upon import (instead of RGBA_ASTC8X8_UFloat) and consequently is not rendered properly.

So my question is: How can a precompressed HDR ASTC texture be imported properly into Unity?

Attached are two sample files.
test3_linear_ldr.astc is a precompressed linear-LDR astc texture with 8x8 block
test3_hdr.astc is a precompressed HDR astc texture with 8x8 block

 

I did solve it using a Scripted importer. It would be neat though if unity would support it in the future.

Code (CSharp):

1. using UnityEngine;
2. using UnityEngine.Assertions;
3. using UnityEditor.AssetImporters;
4. using System.IO;
5.  
6.   ///<summary>
7.   /// Unity can natively import .astc files, but it doesn't handle hdr encoded astc files correctly.
8.   /// Rename the file to .hdrastc in order to use this importer instead.
9.   ///</summary>
10.   [ScriptedImporter(version: 1, ext: "hdrastc")]
11.   public class HDRAstcImporter : ScriptedImporter
12.   {
13.     private static uint ReadUInt24(BinaryReader reader) {
14.       byte b1 = reader.ReadByte();
15.       byte b2 = reader.ReadByte();
16.       byte b3 = reader.ReadByte();
17.       return (((uint)b1) << 16) |
18.              (((uint)b2) << 8) |
19.              ((uint)b3);
20.     }
21.  
22.     public override void OnImportAsset(AssetImportContext ctx)
23.     {
24.       byte[] bytes = File.ReadAllBytes(ctx.assetPath);
25.       BinaryReader reader = new BinaryReader(File.Open(ctx.assetPath, FileMode.Open));
26.       // Header contains 16 bytes.
27.       uint magicNumber = reader.ReadUInt32();
28.       Assert.IsTrue(magicNumber == 1554098963, "Must be a proper ASTC file.");
29.       byte blockX = reader.ReadByte();
30.       byte blockY = reader.ReadByte();
31.       byte blockZ = reader.ReadByte();
32.       uint resX = ReadUInt24(reader);
33.       uint resY = ReadUInt24(reader);
34.       uint resZ = ReadUInt24(reader);
35.  
36.       Assert.IsTrue(blockX == blockY &&
37.           (blockX == 4 || blockX == 5 || blockX == 6 || blockX == 8 || blockX == 10 || blockX == 12)
38.           && blockZ == 1, "Only ASTC textures with block sizes 4x4x1, 5x5x1, 6x6x1, " +
39.                           " 8x8x1, 10x10x1 and 12x12x1 are supported. Got " +
40.                           blockX.ToString() + "x" + blockY.ToString() + "x" + blockZ.ToString());
41.  
42.       TextureFormat textureFormat = TextureFormat.RGBA32;
43.       switch(blockX) {
44.         case 4:
45.           textureFormat = TextureFormat.ASTC_HDR_4x4;
46.           break;
47.         case 5:
48.           textureFormat = TextureFormat.ASTC_HDR_5x5;
49.           break;
50.         case 6:
51.           textureFormat = TextureFormat.ASTC_HDR_6x6;
52.           break;
53.         case 8:
54.           textureFormat = TextureFormat.ASTC_HDR_8x8;
55.           break;
56.         case 10:
57.           textureFormat = TextureFormat.ASTC_HDR_10x10;
58.           break;
59.         case 12:
60.           textureFormat = TextureFormat.ASTC_HDR_12x12;
61.           break;
62.         default:
63.           Assert.IsTrue(false);
64.           break;
65.       }
66.  
67.       Texture2D tex = new Texture2D((int)resX, (int)resY, textureFormat, false, true);
68.       byte[] textureData = reader.ReadBytes(int.MaxValue);
69.       tex.LoadRawTextureData(textureData);
70.       ctx.AddObjectToAsset("texture", tex);
71.       ctx.SetMainObject(tex);
72.     }
73.   }
74.