Shader "Skin Shader" {
Properties {
_MainTex ("Diffuse (RGB)", 2D) = "white" {}
_SpecularTex ("Specular (R) Gloss (G) SSS Mask (B)", 2D) = "yellow" {}
_BumpMap ("Normal (Normal)", 2D) = "bump" {}
_BRDFTex ("BRDF Lookup (RGB)", 2D) = "gray" {}
_CurvatureScale ("Curvature Scale", Float) = 0.005
_Fresnel ("Fresnel Value", Float) = 0.2
_BumpBias ("Normal Map Blur Bias", Float) = 1.5
}

SubShader{
Tags { "Queue" = "Geometry" "RenderType" = "Opaque" }

CGPROGRAM

#pragma surface surf SkinShader fullforwardshadows
#pragma target 3.0
#pragma glsl

struct SurfaceOutputSkinShader {
fixed3 Albedo;
fixed3 Normal;
fixed3 NormalBlur;
fixed3 Emission;
fixed3 Specular;
fixed Alpha;
};

struct Input
{
float2 uv_MainTex;
INTERNAL_DATA
};

sampler2D _MainTex, _SpecularTex, _BumpMap, _BRDFTex;
float _BumpBias, _CurvatureScale, _Fresnel;

void surf (Input IN, inout SurfaceOutputSkinShader o)
{
float4 albedo = tex2D ( _MainTex, IN.uv_MainTex );
o.Albedo = albedo.rgb;
o.Normal = UnpackNormal ( tex2D ( _BumpMap, IN.uv_MainTex ) );
o.Specular = tex2D ( _SpecularTex, IN.uv_MainTex ).rgb;

o.NormalBlur = UnpackNormal( tex2Dlod ( _BumpMap, float4 ( IN.uv_MainTex, 0.0, _BumpBias ) ) );
}

inline fixed4 LightingSkinShader( SurfaceOutputSkinShader s, fixed3 lightDir, fixed3 viewDir, fixed atten )
{
s.Normal = normalize( s.Normal );
s.NormalBlur = normalize( s.NormalBlur );

float NdotL = dot( s.Normal, lightDir );
float3 h = normalize( lightDir + viewDir );

float specBase = saturate( dot( s.Normal, h ) );

float fresnel = pow( 1.0 - dot( viewDir, h ), 5.0 );
fresnel += _Fresnel * ( 1.0 - fresnel );

float spec = pow( specBase, s.Specular.g * 128 ) * s.Specular.r * fresnel;

float2 brdfUV;
float NdotLBlur = dot( s.NormalBlur, lightDir );
brdfUV.x = NdotLBlur * 0.5 + 0.5;
brdfUV.y = _CurvatureScale * dot( _LightColor0.rgb, fixed3(0.22, 0.707, 0.071 ) );
float3 brdf = tex2D( _BRDFTex, brdfUV ).rgb;

float m = atten; // Multiplier for spec and brdf.
m *= saturate( ( (NdotLBlur * 0.5 + 0.5) * 2.0) * 2.0 - 1.0);

fixed4 c;
c.rgb = (saturate(s.Albedo * lerp(saturate(NdotL) * atten, brdf * m, s.Specular.b )) + spec * m) * _LightColor0.rgb * 2;
c.a = 1;
return c;
}

ENDCG
}
FallBack "VertexLit"
}