Shader "Builtin Shadow Caster"
{
    Properties
    {
        _BaseColor ("Base Color", Color) = (1,1,1,1) [Semantic(BaseColor)]
        _Cutoff ("Alpha Cutoff", Range) = 0.5 [Semantic(AlphaCutoff)]
        _MainTex ("Base Map", 2D) = "white" [Semantic(BaseColorTexture)]
    }
    HLSLINCLUDE
    cbuffer PerObjectConstants
    {
        float4x4 gProjectionMatrix;
        float4x4 gViewMatrix;
        float4x4 gModelMatrix;
    };

    cbuffer MaterialConstants
    {
        float4 gBaseColorFactor;
        float4 gAlphaCutoffParams;
    };

    Texture2D BaseColorTexture;
    SamplerState LinearClampSampler;

    struct VSInput
    {
        float3 position : POSITION;
        float3 normal : NORMAL;
        float2 texcoord : TEXCOORD0;
    };

    struct PSInput
    {
        float4 position : SV_POSITION;
        float2 texcoord : TEXCOORD0;
    };

    PSInput MainVS(VSInput input)
    {
        PSInput output;
        const float4 positionWS = mul(gModelMatrix, float4(input.position, 1.0f));
        const float4 positionVS = mul(gViewMatrix, positionWS);
        output.position = mul(gProjectionMatrix, positionVS);
        output.texcoord = input.texcoord;
        return output;
    }

    float MainPS(PSInput input) : SV_Depth
    {
    #ifdef XC_ALPHA_TEST
        const float4 baseColor =
            BaseColorTexture.Sample(LinearClampSampler, input.texcoord) * gBaseColorFactor;
        clip(baseColor.a - gAlphaCutoffParams.x);
    #endif
        return input.position.z;
    }
    ENDHLSL
    SubShader
    {
        Pass
        {
            Name "ShadowCaster"
            Tags { "LightMode" = "ShadowCaster" }
            Cull Back
            ZWrite On
            ZTest LEqual
            HLSLPROGRAM
            #pragma target 4.5
            #pragma vertex MainVS
            #pragma fragment MainPS
            #pragma shader_feature_local _ XC_ALPHA_TEST
            ENDHLSL
        }
    }
}