Question How to get the Main Light Direction in Shader Graph [Built-In RP]

Hello,
I'd like to start using the Shader Graph (version 12.1.8) with the BUILT-IN render pipeline in Unity 2021 LTS (I am using Unity 2021.3.16f).
Unfortunately, the graph is missing some fundamental nodes like getting the direction of the main directional light (only present in shader Graph 13+ from Unity 2022+, https://docs.unity3d.com/Packages/com.unity.shadergraph@13.1/manual/Main-Light-Direction-Node.html).

So I wasted the whole day trying to solve this issue and the best I could find was this CustomLighting.hlsl which it seems like to only work with scriptable render pipelines. (https://github.com/Unity-Technologi...ob/master/Assets/Includes/CustomLighting.hlsl)

My question is, how can I access the _WorldSpaceLightPos0 built-in variable (containing the main light direction) from a node or a custom function node of my graph?
And other variables too like attenuation and directional light color?

Thanks!

 

Did you manage to find a solution for this?
From my limited knowledge about how lighting works in the built-in renderer pipeline, the concept of having a main light doesn't work here, because unlike URP, the built-in renderer pipeline supports having multiple directional lights, so there isn't really a main light. Meanwhile, the entirety of the URP code is all constructed around this idea of having only one directional light in your scene. So I'm trying to find an alternative to that.

 

Hey kcastagnini, have you tried using _WorldSpaceLightPos0 as a parameter in your shader as a input?

 

any one know this? I tried [Main light Directoin Node] in new-version (13.1) of Shader Graph BUT is ALWAYS Zero for built-in RP (default Forward Render Path).

Btw, create a variable reference "_WorldSpaceLightPos0" not works too (compiler error : redefinition of that variable) That SO frustrated!

 

Any news about this? why the function GetMainLight was deprecated without a replace if is important for SSS effects like skin shaders?.

 

Hello, is the Main Light Direction node actually working? Any idea why the value is zero? Thanks.

 

I'm also having issues with this node (I'm using URP). Using a debug node that displays scalar values as a texture, I found that the main directional light was read as [-0.5, -0.5, 0] in the ShaderGraph editor, and [0, 0, -1] in game. Neither of those are the direction of my light in the scene!

 

I've been dealing with something similar (Built-in RP) and here's what I managed to figure out, based on the source code for some built-in shaders.

Most tutorials online for this are for URP it seems, and for URP there's the GetMainLight() method. If you want to get a direction for the sun/main light (assuming you have a custom function with an HLSL), it's:
_WorldSpaceLightPos0.xyz

Here's an hlsl sample I've been trying to get to work from a tutorial.

Code (CSharp):

1. void MainLight_float(float3 WorldPos,out float3 Direction,  out float3 Color, out float DistanceAtten, out float ShadowAtten)
2. {
3. #if SHADERGRAPH_PREVIEW
4.   Direction = float3(0.5, 0.5, 0);
5.    Color = 1;
6.    DistanceAtten = 1;
7.    ShadowAtten = 1;
8. #else
9. #if SHADOWS_SCREEN
10.    float4 clipPos = TransformWorldToHClip(WorldPos);
11.    float4 shadowCoord = ComputeScreenPos(clipPos);
12. #else
13.    float4 shadowCoord = TransformWorldToShadowCoord(WorldPos);
14. #endif
15. //this function doesn't quite work
16.    Light mainLight = GetMainLight(shadowCoord);
17.    //Direction = mainLight.position;
18.    //Color = _MainLightColor.rgb;
19.    //Direction = mainLight.direction;
20. //get xyz on lightPos?
21.    Direction = _WorldSpaceLightPos0;
22.    //Color = mainLight.color;
23.    //haven't figured out the color yet
24.       Color = 1;
25.    DistanceAtten = unity_ProbesOcclusion.x;
26.    ShadowAtten = mainLight.shadowAttenuation;
27. #endif
28. }

I'm a complete newcomer regarding shaders, but I hope this is of some use to someone.

Edit:
This seems to get the light position, I think further calculations are needed to get the direction from that