Question Can surface shaders do multiple passes, or does it need to be a fragment/vertex shader?

Can surface shaders do multiple passes, or does it need to be a fragment/vertex shader?

As a possible alternative, also, say I have a material that messes with some texels. Can I put a second material on a mesh renderer that grabs that output as it's input?

 

Yes. You can use multiple

#pragma surface

lines in a single SubShader, or mix fragment vertex shader passes with surface shaders.

And you can get a previous pass's output using a grab pass. But you shouldn't as this is extremely expensive.