Unity3d 基于物理渲染Physically-Based Rendering之最终篇

前情提要：

讲求基本算法

Unity3d 基于物理渲染Physically-Based Rendering之specular BRDF

plus篇

Unity3d 基于物理渲染Physically-Based Rendering之实现

最后我们用fragment shader 实现，加上diffuse漫反射，代码和之前的surface差不多，只是多了reflect方向的计算，reflect方向的计算方法为用CG函数库中函数reflect，

float3 reflect(float3 i, float3 n);

i为in入射方向，n为normal发现方向，此处入射方向为view direction。

float3 refDir = reflect(-viewDir,N);

参考了下SIGGRAPH 2013中虚幻引擎的diffuse

他们的方法为new diffuse = diffuse color/π。

把π改为可控参数就好，调成我们想要的效果。

建立了一个外部变量_ReflAmount为cubeMap和diffuse的比重，_ReflAmount越高反射周围景物越明显

这是本文实现效果








_ReflAmount = 0.5




_ReflAmount = 0

有没有要滴出血的感觉？




_ReflAmount = 1

高大上的丝袜黑



_ReflAmount = 1




_ReflAmount = 0




_ReflAmount = 0.5

与unity作比较：

diffuse：



specular：



这是虚幻引擎在SIGGRAPH 2013发表的效果：







可惜我没有那么高大上的模型做实验，可惜了，就用人脸做代替

代码如下：

    Shader "Custom/reflect new ops3" {  
        Properties{  
        _MainTex("Base (RGB)", 2D) = "white" {}  
        _Maintint("Main Color", Color) = (1, 1, 1, 1)  
            _Cubemap("CubeMap", CUBE) = ""{}  
        _SC("Specular Color", Color) = (1, 1, 1, 1)  
            _GL("gloss", Range(0, 1)) = 0.5  
            _nMips("nMipsF", Range(0, 5)) = 0.5  
            _ReflAmount("Reflection Amount", Range(0.01, 1)) = 0.5  
    }  
        SubShader{  
            pass{//平行光的的pass渲染  
            Tags{ "LightMode" = "ForwardBase" }  
            Cull Back  
                CGPROGRAM  
    #pragma vertex vert  
    #pragma fragment frag  
    #include "UnityCG.cginc"  
      
                float4 _LightColor0;  
            samplerCUBE _Cubemap;  
            float4 _SC;  
            float _GL;  
            float4 _Maintint;  
            float _nMips;  
            float _ReflAmount;  
            uniform sampler2D _MainTex;  
            float4 _MainTex_ST;  
            struct v2f {  
                float4 pos : SV_POSITION;  
                float2 uv_MainTex : TEXCOORD0;  
                float3 lightDir : TEXCOORD1;  
                float3 viewDir : TEXCOORD2;  
                float3 normal : TEXCOORD3;  
      
            };  
      
            v2f vert(appdata_full v) {  
                v2f o;  
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);//切换到世界坐标  
                o.normal = v.normal;  
                o.lightDir = ObjSpaceLightDir(v.vertex);  
                o.viewDir = ObjSpaceViewDir(v.vertex);  
                o.uv_MainTex = TRANSFORM_TEX(v.texcoord, _MainTex);  
                return o;  
            }  
    #define PIE 3.1415926535      
      
      
            float4 frag(v2f i) :COLOR  
            {  
                float3 viewDir = normalize(i.viewDir);  
                float3 lightDir = normalize(i.lightDir);  
                float3 H = normalize(lightDir + viewDir);  
                float3 N = normalize(i.normal);  
                float _SP = pow(8192, _GL);  
                float d = (_SP + 2) / (8 * PIE) * pow(dot(N, H), _SP);  
                //  float f = _SC + (1 - _SC)*pow((1 - dot(H, lightDir)), 5);  
                float f = _SC + (1 - _SC)*pow(2, -10 * dot(H, lightDir));  
                float k = min(1, _GL + 0.545);  
                float v = 1 / (k* dot(viewDir, H)*dot(viewDir, H) + (1 - k));  
      
                    float all = d*f*v;  
                //  float3 refDir = N - lightDir / 2;//H  
                    float3 refDir = reflect(-viewDir,N);
                    float3 ref = texCUBElod(_Cubemap, float4(refDir, _nMips - _GL*_nMips)).rgb;//* _ReflAmount;  
                float3 c = tex2D(_MainTex, i.uv_MainTex);  
                float3 diff = dot(lightDir, N);  
            //  diff /= PIE;  
                diff = (1 - all)*diff;  
      
            //  return float4(c *(diff + all), 1)  * _LightColor0;  
                return float4(lerp(c, ref, _ReflAmount) *(diff*_Maintint + all), 1)*_LightColor0;  
            //  return float4(ref*((_Maintint+0.2) * (1 - dot(lightDir, N))) + c *(diff*_Maintint + all), 1)*_LightColor0;  
            //  return float4(lerp(c, ref, _ReflAmount) *(diff*(_Maintint + 0.2)* (1 - dot(lightDir, N)) + all), 1)*_LightColor0;  
            }  
            ENDCG  
        }  
        }  
    }  

----- by wolf96 http://blog.csdn.net/wolf96