// XC_BUILTIN_FORWARD_LIT_D3D12_PS
Texture2D gBaseColorTexture : register(t1);
SamplerState gLinearSampler : register(s1);
Texture2D gShadowMapTexture : register(t2);
SamplerState gShadowMapSampler : register(s2);

cbuffer PerObjectConstants : register(b1) {
    float4x4 gProjectionMatrix;
    float4x4 gViewMatrix;
    float4x4 gModelMatrix;
    float4x4 gNormalMatrix;
    float4 gMainLightDirectionAndIntensity;
    float4 gMainLightColorAndFlags;
};

cbuffer MaterialConstants : register(b2) {
    float4 gBaseColorFactor;
};

cbuffer ShadowReceiverConstants : register(b3) {
    float4x4 gWorldToShadowMatrix;
    float4 gShadowBiasAndTexelSize;
    float4 gShadowOptions;
};

struct PSInput {
    float4 position : SV_POSITION;
    float3 normalWS : TEXCOORD0;
    float2 texcoord : TEXCOORD1;
    float3 positionWS : TEXCOORD2;
};

float ComputeShadowAttenuation(float3 positionWS) {
    if (gShadowOptions.x < 0.5f) {
        return 1.0f;
    }

    float4 shadowClip = mul(gWorldToShadowMatrix, float4(positionWS, 1.0f));
    if (shadowClip.w <= 0.0f) {
        return 1.0f;
    }

    float3 shadowNdc = shadowClip.xyz / shadowClip.w;
    float2 shadowUv = float2(
        shadowNdc.x * 0.5f + 0.5f,
        shadowNdc.y * -0.5f + 0.5f);
    if (shadowUv.x < 0.0f || shadowUv.x > 1.0f ||
        shadowUv.y < 0.0f || shadowUv.y > 1.0f ||
        shadowNdc.z < 0.0f || shadowNdc.z > 1.0f) {
        return 1.0f;
    }

    const float shadowDepth = gShadowMapTexture.Sample(gShadowMapSampler, shadowUv).r;
    const float receiverDepth = shadowNdc.z - gShadowBiasAndTexelSize.x;
    const float shadowStrength = saturate(gShadowBiasAndTexelSize.w);
    return receiverDepth <= shadowDepth ? 1.0f : (1.0f - shadowStrength);
}

float4 MainPS(PSInput input) : SV_TARGET {
    float4 baseColor = gBaseColorTexture.Sample(gLinearSampler, input.texcoord) * gBaseColorFactor;
    if (gMainLightColorAndFlags.a < 0.5f) {
        return baseColor;
    }

    float3 normalWS = normalize(input.normalWS);
    float3 directionToLightWS = normalize(gMainLightDirectionAndIntensity.xyz);
    float diffuse = saturate(dot(normalWS, directionToLightWS));
    float shadowAttenuation = diffuse > 0.0f
        ? ComputeShadowAttenuation(input.positionWS)
        : 1.0f;
    float3 lighting = float3(0.28f, 0.28f, 0.28f) +
        gMainLightColorAndFlags.rgb * (diffuse * gMainLightDirectionAndIntensity.w * shadowAttenuation);
    return float4(baseColor.rgb * lighting, baseColor.a);
}