Synchronizing shader code and C#

Unity can generate HLSL code based on C# structs to synchronize data and constants between shaders and C#. In Unity, the process of generating the HLSL code from C# code is called generating shader includes. When Unity generates shader includes, it parses all the C# files in the project and, for every file that contains a struct with a GenerateHLSL attribute, generates corresponding HLSL code. It places this HLSL code in a file with the same name as the origin, but uses the .cs.hlsl file extension.

Generating shader includes

To generate an HLSL equivalent for a C# struct:

1. Add the GenerateHLSL attribute to the struct. To do this, above the line that declares the struct, add [GenerateHLSL(PackingRules.Exact, false)]. For an example on how to do this, see the sample code below. For more information about the GenerateHLSL attribute, see the API documentation.
2. In the Unity Editor, go to Edit > Render Pipeline > Generate Shader Includes.

The following code example is from the High Definition Render Pipeline (HDRP). It shows an extract of the C# representation of a directional light. The original file is LightDefinition.cs. When Unity generates the HLSL shader code, it places it in a new file called LightDefinition.cs.hlsl.

// LightDefinition.cs

[GenerateHLSL(PackingRules.Exact, false)]
struct DirectionalLightData
{
        public Vector3 positionRWS;
        public uint lightLayers;
        public float lightDimmer;
        public float volumetricLightDimmer;   // Replaces 'lightDimer'
        public Vector3 forward;
        public Vector4 surfaceTextureScaleOffset;
};

// LightDefinition.cs.hlsl

// Generated from UnityEngine.Rendering.HighDefinition.DirectionalLightData
// PackingRules = Exact
struct DirectionalLightData
{
    float3 positionRWS;
    uint lightLayers;
    float lightDimmer;
    float volumetricLightDimmer;
    float3 forward;
    float4 surfaceTextureScaleOffset;
};