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Can't Generate LODs for 8192x8192 Normal Textures.

I think I've discovered a bug trying to generate mipmaps for a normal texture 8192x8192.

Reproduction steps:

1, create a project with a DefaultDeviceSettings.ini file in the config folder with the following settings


(That + sign must be missing from the first line in order to work)

2, Import an 8192x8192 normal texture

3, Open the texture and notice the "Combined LOD Bias" increases to 1, and as a result the displayed resolution below is 4096x4096 alt text

4, If you change the texture group to world you'll see that it works properly, however the texture will appear as a solid purple color. In order to fix this you have to change the compression setting to default. alt text

5, If you go through the rest of the groups you'll see the following results

 World              -8192
 WorldNormalMap     -4096
 WorldSpecular      -8192
 Character          -4096
 CharacterNormalMap -4096
 CharacterSpecular  -8192
 Weapon             -8192
 WeaponNormalMap    -4096
 WeaponSpecular     -8192
 Vehicle            -4096
 VehicleNormalMap   -4096
 VehicleSpecular    -8192
 Cinematic          -4096
 Effects            -8192
 EffectsNotFiltered -8192
 Skybox             -4096
 UI                 -8192
 Lightmap           -4096
 Shadowmap          -8192
 RenderTarget       -4096
 MobileFlattened    -8192
 Terrain_Heightmap  -4096
 Terrain_Weightmap  -8192
 Bokeh              -4096
 2D Pixels          -4096

Further, if you change the Mip Gen Settings to NoMipMaps, you will see that the Displayed size for all of these broken groups will show as 8192, but the Max In-Game will still show 4096.

I suspect two things happened here:

When implementing 8192x8192 texture support the devs noticed that the normal compression algorithm in DX11 (And possibly others) wouldn't support the larger textures.

As a workaround they set it up somehow so that on those groups it automatically increases the LOD Bias to prevent the issue.

Questions I have

  1. Is this a known bug, and is my understanding of what's happening here correct?

  2. If this workaround must live on in the code, wouldn't it be better to increase the CombinedLODBias when you're on a bad compression setting, rather than a particular texture group?

  3. Couldn't a different workaround be developed that used a different compression setting for the highest LOD? Or does all of this LOD generation happen in a black box within DX11?

  4. If this is a DX11 issue, will DX12 support these larger textures?

Product Version: UE 4.12
normallodbias.png (33.1 kB)
worldlodbias.png (32.1 kB)
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asked Jul 19 '16 at 12:22 AM in Bug Reports

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Hi Tom,

I'm not seeing anything specifically wrong in my setup when I adjust the max texture resolution.

  • I've used the in editor tool to generate my device profile by going to Window > Developer Tools > Device Profiles.

  • Then I click on the Save As Default button in the top right. Then if I go back to my Project Folder > Config I'll find a DefaultDevicesProfile.ini file.

  • When I open this and adjust the MAXLODSize to be 8192, save and then restart the editor everything loads for my diffuse and normal map.

My normal map doesn't have a purple look to it. It looks as though I would expect.


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answered Aug 17 '16 at 08:58 PM

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Tim Hobson ♦♦ STAFF
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avatar image MadisonAster Sep 28 '16 at 06:34 PM

This issue has resolved itself for me after I changed machines. My old machine was using a 900 series TitanX extreme edition, while my new machine is using a gtx 1080. I don't have time to go back and triple check everything, but I currently suspect that my hardware was the issue. If anyone else encounters this, I would start there.

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