tex3Dlod in Metal broken for years

Do you have plans to fix tex3Dlod in Metal in Unity? This is still broken, has been for years, as of 2019.1.10...

 

Consider submitting bug report

 

Already submitted a while ago...

 

Might not do anything, but you could try writing your shader in D3D11 HLSL using _textureObject.SampleLevel(sampler, uvw, lod) instead of tex3Dlod(_samplerObject, float4(uvw, lod)).

Code (csharp):

1. // define texture and sampler state objects separately instead of using a single sampler3D
2. Texture3D _My3DTexture;
3. SamplerState sampler_My3DTexture;
4.  
5. // in the vert or frag function
6. half4 col = _My3DTexture.SampleLevel(sampler_My3DTexture, uvw, lod);

Most likely this still won't work, but it's worth a try?

 

I have tracked this down to a combination of tex3Dlod and using a "continue" statement in a for loop. Removing the continue statement, while making the result look not quite right, does fix the tex3D lookup. Any ideas why this would happen only on metal? OpenGL and DX and Vulkan are quite happy with the continue statement. No shader warnings or errors on any platform, including MAC and iOS.

From what I can tell, the continue statement is getting the shader in a funny state where it will pop out of the entire for loop early, regardless of whether the continue statement is executed. Probably due to the shader running all the code regardless of if statements maybe? I would have expected the continue to not fire at all, as I wrapped it in an if statement around a uniform that was set to 0.

The for loop and all the if statements had UNITY_LOOP and UNITY_BRANCH applied.

Now that I have identified the problem, I have rewritten the shader to not use a continue, but to apply if statements further down inside the for loop to skip sections using a new variable. I will test WebGL to see if it is fixed by this also and post back.

 

WebGL is still broken even without the continue statement. Tex3Dlod just does not work in WebGL 1.0 or 2.0 at all.

 

Clouds on metal! Now if we can get WebGL working with tex3Dlod that will be amazing!

 

Is there a bug logged for this anywhere so I can track whether this ever gets fixed? Many customers want WebGL with these clouds, but right now it is impossible...

 

Hi all, thanks for this thread. The Metal variant of the bug is still marked Wont Fix, thought I would confirm that it is still open and/or check if theres a new status. Thanks!