Shader "Unlit URP Shader"
{
    Properties
    {
        _BaseColor("Base Color",color) = (1,1,1,1)
        _BaseMap("BaseMap", 2D) = "white" {}
        _Thickness("Thickness",2D)="white"{}
        _MatCap("MatCap",2D)="white"{}
        
        _NormalDistortion("NormalDistortion",Range(0.1,5))=1
        _SSSPower("SSSPower",Range(0.1,5))=1
        _SSSScale("_SSSScale",Range(0.1,5))=1
    }
 
    SubShader
    {
        Tags { "Queue"="Geometry" "RenderType" = "Opaque"  "RenderPipeline" = "UniversalPipeline" }
        LOD 100
 
        Pass
        {
            Tags {"LightMode" = "UniversalForward"}
            HLSLPROGRAM
            // Required to compile gles 2.0 with standard srp library
            #pragma prefer_hlslcc gles
            #pragma exclude_renderers d3d11_9x
            
            #pragma multi_compile _ LIGHTMAP_ON
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS //接受主光源阴影
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS_CASCADE //投射主光源的阴影
            #pragma multi_compile _ _SHADOWS_SOFT //软阴影
            #pragma multi_compile _ _ADDITIONAL_LIGHTS //附加光源
            
            #pragma vertex vert
            #pragma fragment frag

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

 
 
            struct Attributes
            {
                float4 positionOS       : POSITION;
                float2 uv               : TEXCOORD0;
                float3 normal:NORMAL;
            };
 
            struct Varyings
            {
                float4 positionCS       : SV_POSITION;
                float2 uv               : TEXCOORD0;
                float3 Wnormal          : TEXCOORD1;
                float3 Wpos:TEXCOORD2;
            };
 
            CBUFFER_START(UnityPerMaterial)
            half4 _BaseColor;
            float4 _BaseMap_ST;
            CBUFFER_END
            TEXTURE2D (_BaseMap);SAMPLER(sampler_BaseMap);
            TEXTURE2D (_Thickness);SAMPLER(sampler_Thickness);
            TEXTURE2D (_MatCap);SAMPLER(sampler_MatCap);
            float _NormalDistortion;
            float _SSSPower;
            float _SSSScale;
            Varyings vert(Attributes v)
            {
                Varyings o = (Varyings)0;
 
                o.positionCS = TransformObjectToHClip(v.positionOS.xyz);
                o.uv = TRANSFORM_TEX(v.uv, _BaseMap);
                o.Wpos = TransformObjectToWorld(v.positionOS);
                o.Wnormal=TransformObjectToWorldNormal(v.normal);
 
                return o;
            }
 
            half4 frag(Varyings i) : SV_Target
            {
                half4 c;
                half4 baseMap = SAMPLE_TEXTURE2D(_BaseMap, sampler_BaseMap, i.uv);
                c = baseMap * _BaseColor;
                float3 L=normalize(_MainLightPosition);
                float3 V=normalize(_WorldSpaceCameraPos.xyz-i.Wpos.xyz);
                float3 N=normalize(i.Wnormal);
                float3 H=normalize(V+L);
                //float3 
                float3 Back=-normalize(L+N*_NormalDistortion);
                float NdV=pow(1-saturate(dot(N,V)),3)*0.2;
                float NdL=dot(N,L)*0.5+0.5;
                float NdH=pow(saturate(dot(N,H)),2)*0.1;
                float VdB=pow(saturate(dot(V,Back)),_SSSPower)*_SSSScale;
                float thickness=1-SAMPLE_TEXTURE2D(_Thickness,sampler_Thickness,i.uv).r*0.5;
                float3 sss=max(VdB,0.5)*thickness*_BaseColor;

                float3 reflectVec=reflect(-V,N);
                half4 rgbm = SAMPLE_TEXTURECUBE_LOD(unity_SpecCube0,samplerunity_SpecCube0,reflectVec, 4);
                float3 iblSpecular = DecodeHDREnvironment(rgbm, unity_SpecCube0_HDR);

                float3 viewNorm = normalize(mul((i.Wnormal),(float3x3)UNITY_MATRIX_I_V));
                float3 viewPos = normalize(TransformWorldToView(i.Wpos).xyz);
                float3 viewCross = cross(viewPos, viewNorm);
                viewNorm = float3(-viewCross.y, viewCross.x, 0.0);
                float2 matCapUV = viewNorm.xy* 0.5 + 0.5;
                half4 matCap = min(SAMPLE_TEXTURE2D_LOD(_MatCap, sampler_MatCap, matCapUV,2),0.5);

                //次表面散射+漫反射+高光+环境高光+matcap高光采样
                c.rgb = sss+NdL*_BaseColor*_MainLightColor*0.5+NdH*_MainLightColor*saturate(dot(N,L))+iblSpecular*0.2+matCap*max(NdL,0.3)+NdV*_BaseColor;

                
                return c;
            }
            ENDHLSL
        }
    }
}