Resolved shader graph alpha testing issue with selection outline shader and lightmapping

no matter if i use shader graph or write a shader manually: when it uses alpha testing neither the editor selection outline shader gives me a proper alpha tested preview nor the progressive light mapper will take alpha testing into account (enlighten does).
i wonder what it needs to make this work...

 

from HDPR:
// HACK: GI Baking system relies on some properties existing in the shader ("_MainTex", "_Cutoff" and "_Color") for opacity handling, so we need to store our version of those parameters in the hard-coded name the GI baking system recognizes.

adding these fixed lightmapping and the outline selection shader.

 

Is this still the case? Because I'm wondering some of my GI is a bit off and I'm using a lot of Shadergraphs. Such things should be highly documented by Unity ...

 

agreed.
you find some hints in the hdrp shader code (comments).
and i think it is still the case, yes.

 

Yeah... Doesn't work in URP

 

Anyone found a solution to this for URP? This is extremely frustrating :S

 

With URP I was able to make the alpha clip work in lightmap shadows by properly naming the input parameters to "_MainTex", "_Cutoff" and "_Color" in their "reference" name.



However, anything you do in the graph with that _Cutoff value before connecting it to to the Alpha Clip Threshold pin is ignored since the light mapper only looks at the input value in the material it seems.

The underlying issue is reported here:
https://issuetracker.unity3d.com/is...graphs-is-not-factored-in-during-lightmapping

But it is in postponed state....

 

you should be able to tweak the alpha value instead and keep the _Cutoff value untouched?!

 

Possibly, but in my use case it doesn't matter so I have not tried it. I would not be surprised if the light mapper ignores that too and fetches _MainTex and _Color directly to do the clip.

 

I just did a quick test, and indeed, the light mapper ignores what goes on in the graph. It probably reads the input parameters ("_MainTex", "_Cutoff" and "_Color") and emulates the clip that would happen if you had used a standard shader. So if you do anything special in your graph to manipulate the alpha it wont be taken into account.

 

So, so jenky.

We already have to write a dozen passes across SRPs that could handle this case, why not just use one of them instead?

 

I am making a custom URP shader based on Cyanilux's tutorial and templates. Before that I was using Amplify Shader Editor and the URP PBR Template. In both cases I was facing the baked shadows not affected by alpha clipping issue.

Found out that simply setting the RenderType Tag to "TransparentCutout" in the SubShader solves the issue.
I named my properties _BaseMap, _BaseColor and _Cutoff and have no problem with that (at least in Unity 2021.3.0f1 / URP 12.1.6)
Can be done via script / custom shader GUI:

Code (CSharp):

1. material.SetOverrideTag("RenderType", "TransparentCutout");

Hope it helps