Cook-Torrance光照模型

Shader "JQM/Cook-Torrance"
{
    Properties
    {
        _Color("Base Color",Color) = (1,1,1,1)
        _MainTex ("Texture", 2D) = "white" {}

        _Roughness("Roughness",Range(0,1)) = 1
        _Fresnel("Fresnel",Range(0,1)) = 1
        _K("K",Range(0,1)) = 1
    }

    
    SubShader
    {

        Pass
        {
            Tags { "LightMode" = "ForwardBase"}
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            
            #include "UnityCG.cginc"

            float4 _Color;
            //使用Unity定义的变量:灯光
            uniform float4 _LightColor0;


            float _Roughness;
            float _Fresnel;
            float _K;

            struct VertexOutput
            {
                float4 pos : SV_POSITION;
                float4 posWorld : TEXCOORD1;
                float2 uv : TEXCOORD2;
                float3 normal:Normal;
                
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

            VertexOutput vert (appdata_full v)
            {
                VertexOutput o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                o.posWorld = mul(_Object2World, v.vertex);
                o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
                o.normal = v.normal;

                return o;
            }

            fixed4 frag (VertexOutput i) : COLOR
            {
                //将法线转到世界空间:乘以变换矩阵的逆的转置
                //float3 normalWorld  = mul(_Object2World,i.normal);
                float3 normalWorld  = mul(i.normal,_World2Object);

                //观察者
                float3 eyeDir = normalize(_WorldSpaceCameraPos -i.posWorld).xyz;

                //光源
                float3 lightDir = normalize(_WorldSpaceLightPos0).xyz;

                fixed4 col = tex2D(_MainTex, i.uv);

                ///计算漫反射
                float3 diffuse = _Color*saturate(dot(lightDir,normalWorld))*_LightColor0/3.14 ;

                //计算高光
                //float3 h = (eyeDir+lightDir)/2;
                //float3 r = normalize(reflect(-lightDir,normalWorld));
                //float3 specular = saturate(dot(lightDir,normalWorld))* _SpecularColor * pow(saturate(dot(r,eyeDir)),_SpecularPower);

                //计算Cook-Torrance高光
                float s;
                float ln = saturate(dot(lightDir,normalWorld));

                if(ln > 0.0)//在光照范围内
                {
                    float3 h = normalize(eyeDir+lightDir);
                    float nh = saturate(dot(normalWorld, h));
                    float nv = saturate(dot(normalWorld, eyeDir));                
                    float vh = saturate(dot(eyeDir, h));
                    
                    //G项
                    float nh2 = 2.0*nh;
                    float g1 = (nh2*nv)/vh;
                    float g2 = (nh2*ln)/nh;
                    float g = min(1.0,min(g1,g2));

                    //D项：beckmann distribution function
                    float m2 = _Roughness*_Roughness;
                    float r1 = 1.0/(4.0 * m2 *pow(nh,4.0));
                    float r2 = (nh*nh -1.0)/(m2 * nh*nh);
                    float roughness = r1*exp(r2);

                    //F项
                    float fresnel = pow(1.0 - vh,5.0);
                    fresnel *= (1.0-_Fresnel);
                    fresnel += _Fresnel;
                    s = saturate((fresnel*g*roughness)/(nv*ln*3.1415926));
                }
                
                float3 specular =_LightColor0*ln*(_K + s*(1-_K));
                float3 final = _K*diffuse + specular + UNITY_LIGHTMODEL_AMBIENT.xyz;
                return float4(final,1);
            }
            ENDCG
        }
    }
}