Replacement shader for camera --> only touch alpha, leave rest as is

Hey guys,

I was wondering if I could use a replacement shader to ONLY change the values in the alpha channel and leave the RGB values as they would be without the replacement shader.

Basically I am trying to switch the alpha channel and put in the depth value. What I am doing right now is to render just twice, once for the standard view of the camera with RGBA and one time to get the depth texture into RGB of another texture to then access it.

Because I don't need the alpha anyway I want to render just once, having depth in the alpha channel. What I got right now is like changing the whole camera-shader, which ends up having the RGB values changed as well...

 

Well, not really, but besides that:
- 8 bits is usually not enough for depth. You're likely to run into serious precision issues.
- You can just access the z-buffer for the depth:
https://docs.unity3d.com/Manual/SL-CameraDepthTexture.html

 

Thanks. Yeah I'm gonna go for float texture probably, so there won't be precision loss.
Accessing z-buffer is not my problem either, that's fine, I just do not know how to not affect the other channels when I replace the shader of the camera with the custom one.

 

There isn't really a shader of the camera. Materials have shaders and then there are postprocessing shaders.

You can write to alpha only using ColorMask A.

When you just want to write to the z-buffer and not to the color buffer, just remove SV_Target as target and only keep SV_Depth.