Make a shader compatible with the Material Validator in the Built-In Render Pipeline

The Material Validator works with any Materials that use Unity’s Standard shader or surface shadersA streamlined way of writing shaders for the Built-in Render Pipeline. More info
See in Glossary. However, custom shadersA program that runs on the GPU. More info
See in Glossary require a pass named “META”. Most custom shaders that support lightmapping already have this pass defined. See documentation on Lightmapping and shaders for more details.

Carry out the following steps to make your custom shader compatible with the Material Validator:

1. Add the following pragma to the meta pass: #pragma shader_feature EDITOR_VISUALIZATION
2. In the UnityMetaInput structure, assign the specular colorThe color of a specular highlight.
   See in Glossary of the Material to the field called SpecularColor, as shown in the code example below.

Here is an example of a custom meta pass:

Pass
{
    Name "META" 
    Tags { "LightMode"="Meta" }

    Cull Off

    CGPROGRAM
    #pragma vertex vert_meta
    #pragma fragment frag_meta

    #pragma shader_feature _EMISSION
    #pragma shader_feature _METALLICGLOSSMAP
    #pragma shader_feature _ _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A
    #pragma shader_feature ___ _DETAIL_MULX2
    #pragma shader_feature EDITOR_VISUALIZATION

    float4 frag_meta(v2f_meta i) : SV_TARGET
    {
        UnityMetaInput input;
        UNITY_INITIALIZE_OUTPUT(UnityMetaInput, input);
        float4 materialSpecularColor = float4(1.0f, 0.0f, 0.0f, 1.0f);
        float4 materialAlbedo = float4(0.0f, 1.0f, 0.0f, 1.0f);
        input.SpecularColor = materialSpecularColor;
        input.Albedo = materialAlbedo;

        return UnityMetaFragment(input);
    }  
}