Question HDRP10 + DepthOnly Pass + Smoothness?

Hello,

Following some discussions with some other developers, we noticed something interesting and I'm hoping somebody could explain this:

1. I created a basic shader with SG and hooked some heavy noises to the Smoothness


2. I copied the code to a new shader and stripped out everything except the DepthOnly pass. Here I noticed that the Smoothness is calculated:


3. When Compile and Show Code, I can see all that code calculated with some keywords in the PS.



Is this correct/expected? I attached the shader just in case.

Thank you!

 

Just a follow-up with URP 10:

1. The same shader used, the heavy noise is linked to the Smoothness port:


2. I copied the code to a new shader and stripped out everything except the DepthOnly pass. Here I noticed that the Smoothness is not calculated:


3. When Compile and Show Code, it looks as expected:


Shader attached. Thanks you!

 

For our project, we use HDRP and Deferred shading. Since we use a lot of vegetation and heavy shaders, we enabled the depth pass for early z rejection explicitly.
I expect the pixel shaders to be as simple as possible (writing the z output considering the alpha clip values), but instead a ton of unexpected instructions are generated as the OP explained.
Please advise!

 

Furthur checking the HDRP shader in Render Doc, this is what I get:



HDRP Settings + DX 11:


Frame Settings:


Frame Debugger:


I attached the full shader.