Resolved RenderTexture is active but still get a black image after using a compute shader

Hello,

I'm not sure it is here I should post this.

I have a compute shader that does computation on textures and stores the result into a RenderTexture. I then retrieve the renderTexture into a Texture2D.
I'm doing the same process several times in a loop with different input but the same output RenderTexture.

My problem is that I have to do RenderTexture.active = destRenderTexture; after every use of the compute shader or the output image is black. The profiler tells me that setting the active renderTexture takes a lot of time so I would like to set it once at the beginning and get the output after every computation of the compute shader.

Here are somes parts of the code

Code (CSharp):

1. RenderTexture destRenderTexture = new RenderTexture(2048, 2048, 0, RenderTextureFormat.ARGBHalf);
2. destRenderTexture.enableRandomWrite = true;
3. destRenderTexture.Create();
4. destRenderTexture.name = "outputRenderTexture";
5. RenderTexture.active = destRenderTexture;
6.  
7. for(...)
8. {
9.    // set Input data
10.   // set  compute shader parameters
11.   shader..SetFloats("scale", _intensityArray);
12.   ...
13.   shader.SetTexture(shader.FindKernel("ComputeShader"), "dstTex", destRenderTexture);
14.  
15.    shader.Dispatch(0, 2048 / 8, 2048 / 8, 1);
16.  
17.   if(RenderTexture.active !=null)
18.   {
19.     // RenderTexture.active.name is outputRenderTexture
20.     Debug.Log("RenderTexture " + RenderTexture.active.name + " size " + RenderTexture.active.width + " " + RenderTexture.active.height);
21.   }
22.  
23.   // If I uncomment this it works correctly, otherwise I get a black image
24.   // RenderTexture.active = destRenderTexture;
25.  
26.   Texture2D resultTexture = new Texture2D(destRenderTexture.width, destRenderTexture.height, TextureFormat.RGBAHalf, true);
27.                            
28.    resultTexture.ReadPixels(new Rect(0, 0, destRenderTexture.width, destRenderTexture.height), 0, 0);
29.    resultTexture.Apply();
30. }

I don't understand the reason to set everytime the active RenterTexture. Especially, that RenderTexture.active is already equal to my RenderTexture.

 

Did you figure it out?

 

I haven't yet. So I set the active texture every time.

Actually, I have an error when I don't set the active texture every time:

[d3d11] attempting to ReadPixels outside of RenderTexture bounds! Reading (0, 0, 2048, 2048) from (1065, 691)

I don't know where (1065, 691) comes from.
I check the RenderTexture.active and it is not null and its size is (2048, 2048).

 

I don't use ReadPixel anymore. I use Graphics.CopyTexture to copy the RenderTexture to the Texture2D. It seems to be faster but I don't know if it is correct to use it that way. But I don't need to set active render texture anymore.
I also use a temporary renderTexture instead of creating a new one. It still not super fast but it is faster than before.

here is the code.

Code (CSharp):

1.   RenderTextureDescriptor renderTextureDescriptor = new RenderTextureDescriptor(2048, 2048, RenderTextureFormat.ARGBHalf);,
2.   renderTextureDescriptor.enableRandomWrite = true;
3.   RenderTexture destRenderTexture = RenderTexture.GetTemporary(renderTextureDescriptor);
4.    
5.     for(...)
6.     {
7.        // set Input data
8.       // set  compute shader parameters
9.       shader..SetFloats("scale", _intensityArray);
10.       ...
11.       shader.SetTexture(shader.FindKernel("ComputeShader"), "dstTex", destRenderTexture);
12.    
13.        shader.Dispatch(0, 2048 / 8, 2048 / 8, 1);
14.    
15.       Texture2D resultTexture = new Texture2D(destRenderTexture.width, destRenderTexture.height, TextureFormat.RGBAHalf, true);
16.       Graphics.CopyTexture(destRenderTexture, resultTexture);                          
17.     }                              
18. RenderTexture.ReleaseTemporary(destRenderTexture);
19.  

 

I have submitting a bug using the bug report from the editor.
ticket: 1277899_8dsku3fska9d9p63