Unity Shader: Cook-Torrance

// 原公式来自于 GPU 编程与CG 语言之阳春白雪下里巴人 的 114页的（10-11）。公式中的分母少了个 （N·L），具体看 113 页的公式（10-3）。

 1 Shader "Custom/Cook-Torrance" {
 2     Properties {
 3         _MainTex("Main Tex", 2D) = "white" {}
 4         _AmbiColor ("Main Color", Color) = (1, 1, 1, 1)
 5         _Ak ("Ambient Coef", float) = 1
 6         _DiffColor ("Diff Color", Color) = (1, 1, 1, 1)
 7         _Dk ("Diff Coef", float) = 1
 8         _SpecColor ("Spec Color", Color) = (1, 1, 1, 1)
 9         _Sk ("Sk", float) = 1
10         // _Sp ("Sp", Range(0, 5)) = 1
11         _m ("m", Range(0, 1)) = 0.1
12         _f0 ("f0", Range(0, 1)) = 0.5
13     }
14 
15     SubShader {
16         Tags { "RenderType"="Opaque" }
17         LOD 200
18         Pass {
19             CGPROGRAM
20             #include "UnityCG.cginc"
21             #pragma vertex vert
22             #pragma fragment frag
23 
24             float4 _AmbiColor;
25             float _Ak;
26             float4 _DiffColor;
27             float _Dk;
28             float4 _SpecColor;
29             float _Sk;
30             // float _Sp;
31             float _m;
32             float _f0;
33 
34             sampler2D _MainTex;
35 
36             struct v2f {
37                 float4 pos : POSITION;
38                 float2 uv : TEXCOORD0;
39                 float3 light : TEXCOORD1;
40                 float3 view : TEXCOORD2;
41                 float3 normal : TEXCOORD3;
42             };
43 
44             v2f vert(appdata_base v) {
45                 v2f o;
46                 o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
47                 o.normal = v.normal;
48                 o.light = ObjSpaceLightDir(v.vertex);
49                 o.view = ObjSpaceViewDir(v.vertex);
50                 o.uv = v.texcoord;
51 
52                 return o;
53             }
54 
55             float4 frag(v2f i) : COLOR {
56                 float3 l = normalize(i.light);
57                 float3 v = normalize(i.view);
58                 float3 n = normalize(i.normal);
59                 float3 h = normalize(l + v);
60 
61                 float vh = dot(v, h);
62                 float nh = dot(n, h);
63                 float nl = dot(n, l);
64                 float nv = dot(n, v);
65 
66                 float4 t = tex2D(_MainTex, i.uv);
67 
68                 float4 ambi = _AmbiColor * _Ak;
69                 float4 diff = _DiffColor * _Dk * saturate(nl);
70 
71                 if (nh <= 0 || nl <= 0)
72                     return t * ambi + diff;
73 
74                 float F = _f0 + (1 - _f0) * (1 - pow(vh, 5));
75                 float D = exp((nh * nh - 1) / (_m * _m * nh * nh)) / (_m * _m * pow(nh, 4));
76                 float G = min(1, min(2 * nh * nl / vh, 2 * nh * nv / vh));
77 
78                 float R = F * D * G / (nv * nl);
79 
80                 float spec = _SpecColor * _Sk * R * nl;
81 
82                 return t * ambi + diff + spec;
83             }
84 
85             ENDCG
86         }
87     } 
88     FallBack "Diffuse"
89 }