[Solved] Compute shader on Android not working

I've spent the last couple days trying to figure out why my compute shader isn't working on Android. I've narrowed it down to the `tex2dlod` call always returning 0. Here's a minimal example:

Code (CSharp):

1. #pragma kernel NotWorking
2.  
3. RWTexture2D<float4> result;
4.  
5. float tex_width;
6. float tex_height;
7. sampler2D input;
8.  
9. [numthreads(8,8,1)]
10. void NotWorking (uint3 id : SV_DispatchThreadID) {
11.     float2 uv = float2(id.x / tex_width, id.y / tex_height);
12.     float4 sample = tex2Dlod(input, float4(uv.x, uv.y, 0, 0));
13.     result[id.xy] = sample;
14. }

On desktop, the output is the `result` texture being a copy of the `input` texture. As soon as I build/deploy to Android, `result` is just a blank (black) texture. I know the compute shader is getting executed because if I remove the `tex2Dlod` and replace it with a constant, I get the expected result on both platforms. EDIT: Turns out `tex2Dlod` wasn't to blame. I had replaced it with float4(1,1,1,1) and that was working but other values were not. Solution below.

What am I doing wrong?!

 

@aleksandrk filed report 1214413. Thanks!

 

I spent a long time playing with all the variables I could. In the end, the one that made the shader start working was to change the format on the RenderTexture that I was using to write `result` into:

Code (CSharp):

1. renderTexture.format = RenderTextureFormat.RFloat;
2.  

The default `RenderTextureFormat` doesn't work on Android (gives error `RENDERTEXTURE.CREATE FAILED: FORMAT UNSUPPORTED FOR RANDOM WRITES - RGBA4 UNORM (7)`). I had originally tried replacing it with `RenderTextureFormat.ARGB32` since that's the most common one. Turns out that doesn't work either. Maybe it needs a different declaration in the compute shader? I don't know - it all worked in the editor...