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Conversation: Unity URP Shader Development

Human:

Can you write me a simple lit URP shader for unity with a normal, base, and metalic maps

Assistant:

Certainly. Here's a simple lit URP (Universal Render Pipeline) shader for Unity that includes normal, base (albedo), and metallic maps. I'll provide the shader code using ShaderLab syntax with HLSL:

Shader "Custom/SimpleLitURP"
{
    Properties
    {
        _BaseMap ("Albedo (RGB)", 2D) = "white" {}
        _BaseColor ("Color", Color) = (1,1,1,1)
        _Metallic ("Metallic", Range(0,1)) = 0.0
        _Smoothness ("Smoothness", Range(0,1)) = 0.5
        _NormalMap ("Normal Map", 2D) = "bump" {}
        _NormalStrength ("Normal Strength", Float) = 1.0
    }
    SubShader
    {
        Tags {"RenderType"="Opaque" "RenderPipeline"="UniversalPipeline"}
        LOD 300

        HLSLINCLUDE
        #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
        #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
        ENDHLSL

        Pass
        {
            Name "ForwardLit"
            Tags {"LightMode"="UniversalForward"}

            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS_CASCADE
            #pragma multi_compile _ _ADDITIONAL_LIGHTS_VERTEX _ADDITIONAL_LIGHTS
            #pragma multi_compile_fragment _ _ADDITIONAL_LIGHT_SHADOWS
            #pragma multi_compile_fragment _ _SHADOWS_SOFT

            struct Attributes
            {
                float4 positionOS   : POSITION;
                float3 normalOS     : NORMAL;
                float4 tangentOS    : TANGENT;
                float2 uv           : TEXCOORD0;
            };

            struct Varyings
            {
                float2 uv           : TEXCOORD0;
                float4 positionCS   : SV_POSITION;
                float3 positionWS   : TEXCOORD1;
                float3 normalWS     : TEXCOORD2;
                float4 tangentWS    : TEXCOORD3;
            };

            TEXTURE2D(_BaseMap);
            SAMPLER(sampler_BaseMap);
            TEXTURE2D(_NormalMap);
            SAMPLER(sampler_NormalMap);

            CBUFFER_START(UnityPerMaterial)
                float4 _BaseMap_ST;
                half4 _BaseColor;
                half _Metallic;
                half _Smoothness;
                half _NormalStrength;
            CBUFFER_END

            Varyings vert(Attributes IN)
            {
                Varyings OUT;
                UNITY_SETUP_INSTANCE_ID(IN);
                UNITY_TRANSFER_INSTANCE_ID(IN, OUT);

                VertexPositionInputs positionInputs = GetVertexPositionInputs(IN.positionOS.xyz);
                VertexNormalInputs normalInputs = GetVertexNormalInputs(IN.normalOS, IN.tangentOS);

                OUT.positionCS = positionInputs.positionCS;
                OUT.positionWS = positionInputs.positionWS;
                OUT.normalWS = normalInputs.normalWS;
                OUT.tangentWS = float4(normalInputs.tangentWS, IN.tangentOS.w);
                OUT.uv = TRANSFORM_TEX(IN.uv, _BaseMap);
                return OUT;
            }

            half4 frag(Varyings IN) : SV_Target
            {
                half4 albedo = SAMPLE_TEXTURE2D(_BaseMap, sampler_BaseMap, IN.uv) * _BaseColor;
                half3 normalTS = UnpackNormalScale(SAMPLE_TEXTURE2D(_NormalMap, sampler_NormalMap, IN.uv), _NormalStrength);

                float3 bitangent = normalize(cross(IN.normalWS, IN.tangentWS.xyz) * IN.tangentWS.w);
                float3x3 TBN = float3x3(normalize(IN.tangentWS.xyz), bitangent, IN.normalWS);
                float3 normalWS = normalize(mul(normalTS, TBN));

                InputData inputData = (InputData)0;
                inputData.positionWS = IN.positionWS;
                inputData.normalWS = normalWS;
                inputData.viewDirectionWS = GetWorldSpaceNormalizeViewDir(IN.positionWS);
                inputData.shadowCoord = TransformWorldToShadowCoord(IN.positionWS);

                SurfaceData surfaceData = (SurfaceData)0;
                surfaceData.albedo = albedo.rgb;
                surfaceData.alpha = albedo.a;
                surfaceData.metallic = _Metallic;
                surfaceData.smoothness = _Smoothness;
                surfaceData.normalTS = normalTS;

                half4 color = UniversalFragmentPBR(inputData, surfaceData);
                return color;
            }
            ENDHLSL
        }

        Pass
        {
            Name "ShadowCaster"
            Tags{"LightMode" = "ShadowCaster"}

            ZWrite On
            ZTest LEqual

            HLSLPROGRAM
            #pragma vertex ShadowPassVertex
            #pragma fragment ShadowPassFragment

            #include "Packages/com.unity.render-pipelines.universal/Shaders/LitInput.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/Shaders/ShadowCasterPass.hlsl"
            ENDHLSL
        }
    }
}