CommandBuffer.Blit(source, dest, material) Source Texture is incorrect

I have a shader that I use through a command buffer to perform a screen-space operation on a Render Texture.

Previously, I was lazy and had a source render texture assigned to a global shader property. Now I'm cleaning up my code and instead of referencing the global property in the shader, I'm trying to read it through _MainTex directly. However, what I'm getting in _MainTex is not the same as the global shader property:

Code (CSharp):

1. //////C Sharp Code Snippit
2. string globalSrcTexPropertyAsString = "_GlobalSrcTexture";
3. string globalDstTexPropertyAsString = "_GlobalDstTexture";
4.  
5. RenderTexture globalSrcTexture = new RenderTexture(Screen.height, Screen.height, 0, RenderTextureFormat.ARGBFloat);
6. RenderTexture globalDstTexture = new RenderTexture(Screen.height, Screen.height, 0, RenderTextureFormat.ARGBFloat);
7.  
8. globalSrcTexture.SetGlobalShaderProperty(globalSrcTexPropertyAsString);
9. globalDstTexture.SetGlobalShaderProperty(globalDstTexPropertyAsString);
10.  
11. CommandBuffer cmdBuffer = new CommandBuffer();
12.  
13. //Some things happen here that write to globalSrcTexture
14.  
15. cmdBuffer.SetRenderTarget(globalDstTexture);
16. effect.ClearRenderTarget(false, true, new Color(0, 0, 0, 1));
17. effect.Blit((Texture)globalSrcTexture, globalDstTexture, blitMaterial);
18.  
19.  
20. //////Shader code snippit
21.  
22. sampler2D_float _MainTex;
23.  
24. //The output of these two methods should be identical, but they're not
25. return tex2D(_GlobalSrcTexture, i.uv);
26. return tex2D(_MainTex, i.uv);

Why are the two fragment outputs in the shader not identical?

 

I ran into that same issue before. _MainTex doesn't seem to get set correctly when using Blit in a CommandBuffer. Using a global does work. I think I just added:

Code (csharp):

1.  
2. cmdBuffer.SetGlobalTexture("_MainTex", sourceIdentifier);
3.  

Not the greatest way, but it does the trick.

 

Similar issue also reported here:
https://forum.unity3d.com/threads/c...internal_blitcopy-shader.432699/#post-2891602