Question Graphics.Blit with a material is just giving me a big blue box

I've got an unlit shader that generates an image, and I'm trying to get that shader to generate a simple Texture2D that I can then save to disk. I'm using what seems to be standard code, but texture it is giving me is always just a blue box no matter what I change.

Code (CSharp):

1.  
2.     RenderTexture renderTexture = RenderTexture.GetTemporary(res, res, 0);
3.     Texture2D texture = new Texture2D(renderTexture.width, renderTexture.height, TextureFormat.RGBA32, false);
4.     Material m = new Material(baseMat);
5.  
6.     Graphics.SetRenderTarget(renderTexture);
7.     GL.Clear(true, true, Color.black);
8.     Graphics.Blit(texture, renderTexture, m);
9.     Graphics.SetRenderTarget(null);
10.  
11.     RenderTexture.active = renderTexture;
12.     texture.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
13.     texture.Apply();
14.  
15.     GetComponent<Renderer>().material.mainTexture = texture;

What am I missing, here? If I try to write the texture to disk using
tex.EncodeToPNG(); the output it gives me is just a transparent box with nothing in it. My shader is set to generate a simple checkboard pattern, so that's the output I'm expecting.

 

I've solved the problem, or perhaps more correctly, ChatGPT has solved the problem for me.

This needs to be added to the tags of your SubShader:

"RenderTexture"="True"

Or in context:

Code (csharp):

1.  
2. SubShader {
3.         Tags {"Queue"="Transparent" "RenderType"="Opaque" "RenderTexture"="True"}
4.         Pass {
5.             ...

Now, there is a problem if your shader is built in ShaderGraph, as ShaderGraph does not support custom tags for some reason. In my case I ended up rewriting my shader in native code because it was simple, but that thread covers a lot of other possible cases.

My solution here likely also covers previous times when this question has been asked and remained at least partially unresolved:

https://forum.unity.com/threads/render-to-texture-without-a-camera.235053/
https://forum.unity.com/threads/save-texture-generated-by-a-shader.326561/

 

Hm, that's weird. Is that new in the SRP? Definitely wasn't needed in the BIRP. Also can't find any documentation about it.

 

I've heard that Graphics.Blit() is not supported by HDRP or URP, so it should be a hidden feature in BiRP.

 

I'm using URP.

 

Just found something from this thread.

So, it's actually possible to use Graphics.Blit() in SRP, but its behavior may not be the same in BiRP.

 

You can create a renderer feature to generate these textures with shader graph in URP. (check this thread)

 

Graphics.Blit works with a shader graph shader if you specify pass 0 like so:
Graphics.Blit(null, blitTarget, blitMaterial, 0); No need for the RenderTexture=True tag.

 

Thank you! You saved me from madness )