Unity 6.0, how to sample shadow in shader code?

Unity Engine
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1

In Unity 6.0, how to sample shadow in shader code?

I am using the HLSL code below to sample shadow for a custom lighting shader:

// 1) Get shadow coordinates
float4 shadowCoord;
#if SHADOWS_SCREEN
    shadowCoord = ComputeScreenPos(positionCS);
#else
    shadowCoord = TransformWorldToShadowCoord(positionWS);
#endif

// 2) Get the main light
// `GetMainLight` is Supposed to be located in `Universal RP/ShaderLibrary/Lighting.hlsl`
// but I cannot find it there nor in other files
Light light = GetMainLight(shadowCoord, positionWS, 1);

// 3) Do stuff
float3 radiance = light.color * light.shadowAttenuation;
// ...
float3 color = albedo * radiance * (diffuse + specular);
return color;

I am also setting the boolean keyword _MAIN_LIGHT_SHADOWS in the shader graph that calls the code above as a custom function. This keyword is set to “multi-compile” and the default is true.

The code compiles but the shadow is not visible in the resulting game view.

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All this comes from this tutorial (also available as a video) which I tried to reproduce in a new project using the “SRP Universal 3D” template and the Unity version 6000.0.35f1.

As this tutorial is already more than 3 years old, I would expect things to have changed since then and thus the way I am reproducing it now to be wrong in Unity 6. However, after having looked at the library in Universal RP/ShaderLibrary/ I cannot seem to find how to effectively sample shadow with the new version. I see in Lighting.hlsl that now GetMainLight seems to be called with different arguments, on line 291:

Light mainLight = GetMainLight(inputData, shadowMask, aoFactor);

I tried to reproduce this by recreating the “inputData” structure and the other arguments but without success.

Thanks for reading, any help would be appreciated!

2

This is one of the best sources on implementing custom lighting in shader graph.

You can also check my free shadow Receiver URP asset to get a barebones shadow Receiver you can use as a base

3

Thanks for the link, that worked for me!

The thing I was doing wrong is when setting the keywords in the unlit shader graph.
This is well explained in Cyan’s package you posted:

  • Enum Keyword, Global Multi-Compile _MAIN_LIGHT, with entries :
    • SHADOWS
    • SHADOWS_CASCADE
    • SHADOWS_SCREEN
  • Boolean Keyword, Global Multi-Compile _SHADOWS_SOFT

And once the keyword set, choose the right enum type in the material properties.

4

Thanks, I was missing exactly that part!