Limiting the amount of mipmap levels

Is their any way to limit the amount of mipmap levels a texture has? I can't find anyway to do it.

 

There's no way to do it from the texture settings, no. Unity always provides the GPU a full chain of mips if mip maps are enabled. You can import in a premade dds or pvrtc file with a limited mip chain, but this will crash Unity!

The only solution is to limit the mip level manually in the shader by using tex2Dlod and calculating the mip level and clamping it, or using tex2Dgrad and limiting the derivatives.

 

Hi, I saw this in the release notes for 2019.2.0:

Graphics: Added support for partial mipmap chains in texture classes

How can I set the mipmap limit? I don't see any new options in the Texture inspector window.

 

Bump, I don't see this either @richardkettlewell - did we end up getting a public API for this?

 

Bump. If this isn't possible at the moment, despite the 2019.2 changelog, it would at least be good to know!

 

@vandreev Bump!

 

Is there a way try limit the lightmap count after the texture is created? We have a asset post processor for lightmaps, and we'd like the limit the number of mipmaps for lightmaps to prevent bleeding.

 

Awesome, thanks for the info! Is there a way I can save a Texture2D created with the mip count constructor to disk? I only know of the File.Write/Texture2D.EncodeToPNG way which writes mip0 to disk, resulting in the texture importer creating the max mip count. Like a lot of people needing an explicit mip count, I'm trying to save a generated texture atlas to disk.

 

And while we have you here, what about lightmaps? The textures are already created and the only way I can edit the texture is via the importer settings? I can also alter the texture 2D via a post processor but you can't seem to change the mipmap count on an already created texture2d.

 

I don't get it, Is it possible to change the mipCount for the imported texture? Kinda like it's possible to change mipMapBias via TextureImporter?

 

Not currently, no. Only for textures created from script, which can be generated from imported textures, but will have to be new assets. You could conceivably do this as a custom asset processor, but you'd still get two assets, the original imported one with full mips, and script generated one with limited mips.

 

But you will lose the compression in the process @bgolus....I want to use it in texture atlases, to avoid texture bleeding on high mipmap levels, but it defeats the purpose of saving memory if I can't enable compression...Except if there is a way to compress the generated texture?

 

https://docs.unity3d.com/ScriptReference/EditorUtility.CompressTexture.html

 

I tried first to use Texture2D.Compress() but it generates more mipmaps...And they are worse than the original texture...Will try EditorUtility.CompressTexture.

 

Texture2D.Compress()

is intended for real time compression. Basically for content you're importing at runtime on PC. The

EditorUtility.CompressTexture()

should have much better quality, but it may also still blow away your mipmap settings. If it does, then yeah, time to complain to Unity!

If that's still broken you could work around that by compressing each mip individually and using CopyTexture to copy the results into the "real" one. But oy vey that's a massive pain. I'm with you in that I was hoping it'd be exposed on the importer's advanced settings.

 

I agree, that should be just put into texture settings...I will try to compress them individually, I fear nothing!

 

When I try to compress using EditorUtility.CompressTexture Unity crashes with many formats, including DXT1.
Here's the output stack:

Code (CSharp):

1. 0x00007FF708D3EA85 (Unity) prcore::RemapFullPixelShift_RGB888_ARGB8888
2. 0x00007FF708D3BE62 (Unity) prcore::BlitImageRemapNoScale
3. 0x00007FF708D3B95E (Unity) prcore::BlitImage
4. 0x00007FF707BAF5CC (Unity) CompressSingleImageTexture
5. 0x00007FF707BB018C (Unity) CompressTextureWithMultipleImages
6. 0x00007FF708A229AF (Unity) EditorUtility_CUSTOM_CompressTexture
7. 0x000001F1ACF6A210 (Mono JIT Code) (wrapper managed-to-native) UnityEditor.EditorUtility:CompressTexture (UnityEngine.Texture2D,UnityEngine.TextureFormat,int)
8. 0x000001F1ACF6A093 (Mono JIT Code) UnityEditor.EditorUtility:CompressTexture (UnityEngine.Texture2D,UnityEngine.TextureFormat,UnityEditor.TextureCompressionQuality)

any idea why?

 

Is that when using a limited mip range, or always? I can totally imagine it's just straight up broken for the limited mip case.

 

Oh, good point! Only when I want less mipmaps, it crashes...If I use the same amount as the original one, everything is fine...I guess you're right, it's not meant to do that.

 

So, yeah. This means you have to construct a Texture2D with no mips for each mip level, copy the data from the original texture into it. Compress that. Copy each mip into a new Texture2D created with the wanted compressed format and limited mip count.

 

Here's the method I've been using for creating limited mip maps:

Code (CSharp):

1.         public static Texture2D CreateLimitedMipmapsTexture(Texture2D sourceTexture, TextureFormat format, int mipmapCount, bool isLinear, int anisoLevel, FilterMode filterMode)
2.         {
3.             var texturePath = AssetDatabase.GetAssetPath(sourceTexture);
4.          
5.             var limitedMips = new Texture2D(sourceTexture.width, sourceTexture.width, format, mipmapCount, isLinear);
6.             limitedMips.anisoLevel = anisoLevel;
7.             limitedMips.filterMode = filterMode;
8.          
9.             for (var i = 0; i < mipmapCount; i++)
10.             {
11.                 Graphics.CopyTexture(sourceTexture, 0, i, limitedMips, 0, i);
12.             }
13.          
14.             var outputPath = $"{texturePath.Replace($"{sourceTexture.name}.png", $"{sourceTexture.name}__LimitedMipCount-{mipmapCount}.asset")}";
15.          
16.             AssetDatabase.CreateAsset(limitedMips, outputPath);
17.             AssetDatabase.SaveAssets();
18.          
19.             return AssetDatabase.LoadAssetAtPath<Texture2D>(outputPath);
20.         }
21.  

It requires the source texture to already be compressed. It also expects a .png, but you can probably edit the method to extract the file extension, if needed.

 

@hungrybelome looks like it doesn't work for me, at least on the texture preview, there is still like 11 mipmaps level, and all the level above the one I set on the asset creation are corrupted.
Edit: nevermind, it worked once I propertly opened my eyes and fixed my stuff....
So the thing is:
- precompress the texture
- copy each mip you want into a new texture
- save it

Clever!

 

I have a shader based solution for this. My goal was to dynamically limit the highest resolution mip level that could be used. This would essentially be the same as limiting the maximum resolution of the texture.

Code (HLSL):

1. // min is a 2d vector that limits the mip in x and y axes. (1,1) will be the lowest resolution mip, (0,0) is no limit and will use highest res mip
2. inline fixed4 tex2DMinMip(sampler2D tex, float2 uv, float2 min) {
3.     float2 uv_dx = ddx(uv);
4.     float2 uv_dy = ddy(uv);
5.  
6.     if (length(uv_dx) < min.x) uv_dx = normalize(uv_dx)*min.x;
7.     if (length(uv_dy) < min.y) uv_dy = normalize(uv_dy)*min.y;
8.  
9.     return tex2D(tex, uv, uv_dx, uv_dy);
10. }
11.  
12. // example:
13. sampler2D _MainTex;
14. float4 _MainTex_TexelSize;
15. // in fragment shader:
16. fixed4 col = tex2DMinMip(_MainTex, IN.uv_MainTex, 8*_MainTex_TexelSize.xy);
17. // 8 is 2^n where n is desired mip level (3rd highest resolution mip in this example)
18.  

 

Thank you for this! I just ran into the "Texture Atlas doesn't play nice with mipmaps" issue after adding a few more tile textures to my atlas. I was getting worried it was going to be a difficult problem to solve - but hoped that something simple like this was out there.

I added this functionality at runtime along with PackTextures() to create my Texture Atlas.

It works perfectly - thank you!

 

What about rendertexture?
I switched to 2,3,4 with texture mipcount at 3 like your example and it's not being updated by CopyTexture.
blit works though

 

Wait, what? According to the docs, you can only use a single bool mipChain, not an int specifying the mip count.

But... it compiles, at least in 2019.3 (and apparently newer). But doesn't work in 5.6. Hmmm.

I wonder why does it has an "exclude from docs" tag in the reference code
https://github.com/Unity-Technologi...db8ea/Runtime/Export/Graphics/Texture.cs#L678

 

Is there any chance to apply crunch compression to that texture? (With ".asset" extension).

 

The Texture2D.Reinitialize method is lacking the explicit mip count, and it's a problem because there is currently no way to change the mip count of an already created texture.
It would be great if we could have an explicit mip count in Texture2D.Reinitialize.

 

@richardkettlewell Hey, Is there any news on this? How can we limit the MipMaps?

 

Thank you! It works!

 

Also, RTHandle missed mip levels property.

 

I render water with full mip chain (for refraction/volumetric lighting, caustic, etc), but for reflection and normals I need to use my own mipmap limits. Global texture limits can brake most of the other effects (such as third-party fog rendering, FSR/DLSS, etc, etc). Any global limits must be removed, because it leads to undefined behavior.

 

@bgolus once helped me with clamping mip map levels in shader over in this thread here with a very detailed answer. If anyone wants additional reading on the subject, it may help.