首先声明以下素材和shader代码都来自Kerry佬，我只做整理和学习之用，写此随笔是为了做个笔记方便以后查阅。
SH，英文全称Spherical Harmonics Lighting，即球谐光照，主要用来模拟漫反射。
1. 如何计算SH
SH只需要提供一组Vector4数组，便能通过算法来计算出漫反射光，这种方法的好处是适用于没有光照探针的场景中。如计算方法如下：
1 half3 CalcSH(float3 normal_dir, half4 custom_SHAr, half4 custom_SHAg, half4 custom_SHAb, half4 custom_SHBr, half4 custom_SHBg, half4 custom_SHBb, half4 custom_SHC)
2 {
3 float4 normalForSH = float4(normal_dir, 1.0);
4 //SHEvalLinearL0L1
5 half3 x;
6 x.r = dot(custom_SHAr, normalForSH);
7 x.g = dot(custom_SHAg, normalForSH);
8 x.b = dot(custom_SHAb, normalForSH);
9
10 //SHEvalLinearL2
11 half3 x1, x2;
12 // 4 of the quadratic (L2) polynomials
13 half4 vB = normalForSH.xyzz * normalForSH.yzzx;
14 x1.r = dot(custom_SHBr, vB);
15 x1.g = dot(custom_SHBg, vB);
16 x1.b = dot(custom_SHBb, vB);
17
18 // Final (5th) quadratic (L2) polynomial
19 half vC = normalForSH.x*normalForSH.x - normalForSH.y*normalForSH.y;
20 x2 = custom_SHC.rgb * vC;
21
22 float3 sh = max(float3(0.0, 0.0, 0.0), (x + x1 + x2));
23 sh = pow(sh, 1.0 / 2.2);
24 return sh;
25 }
这一组Vector4数组如下：
2. 光照探针
unity中提供了Light Probe，即光照探针，来提前把光照信息烘焙到探针球里，这样物体进入探针区域后，通过取出影响物体的所有探针球，来计算出SH光照。
这是一种比较节省性能的做法。shader中计算SH光照可调用方法 half3 SampleSH(half3 worldNormal);
shader如下：
1 Shader "MyURP/Kerry/SH/URPLightProbe"
2 {
3 Properties
4 {
5 _Tint("Tint",Color) = (1,1,1,1)
6 _Expose("Expose",Float) = 1.0
7 _Rotate("Rotate",Range(0,360)) = 0
8 _NormalMap("Normal Map",2D) = "bump"{}
9 _NormalIntensity("Normal Intensity",Float) = 1.0
10 _AOMap("AO Map",2D) = "white"{}
11 _AOAdjust("AO Adjust",Range(0,1)) = 1
12
13 }
14 SubShader
15 {
16 Tags
17 {
18 "RenderType" = "Opaque"
19 "RenderPipeline" = "UniversalPipeline"
20 }
21 LOD 100
22
23 Pass
24 {
25 Tags
26 {
27 "LightMode" = "UniversalForward"
28 }
29
30 HLSLPROGRAM
31 #pragma vertex vert
32 #pragma fragment frag
33 #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
34 #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
35
36 struct appdata
37 {
38 float4 vertex : POSITION;
39 float2 texcoord : TEXCOORD0;
40 float3 normal : NORMAL;
41 float4 tangent : TANGENT;
42 };
43
44 struct v2f
45 {
46 float2 uv : TEXCOORD0;
47 float4 pos : SV_POSITION;
48 float3 normal_world : TEXCOORD1;
49 float3 pos_world : TEXCOORD2;
50 float3 tangent_world : TEXCOORD3;
51 float3 binormal_world : TEXCOORD4;
52 };
53
54 //sampler2D _MainTex;
55 //float4 _MainTex_ST;
56 TEXTURECUBE(_CubeMap); SAMPLER(sampler_CubeMap);
57 float4 _CubeMap_HDR;
58 float4 _Tint;
59 float _Expose;
60
61 TEXTURE2D(_NormalMap); SAMPLER(sampler_NormalMap);
62 float4 _NormalMap_ST;
63 float _NormalIntensity;
64 TEXTURE2D(_AOMap); SAMPLER(sampler_AOMap);
65 float _AOAdjust;
66 float _Rotate;
67 float _Roughness;
68 TEXTURE2D(_RoughnessMap); SAMPLER(sampler_RoughnessMap);
69 float _RoughnessContrast;
70 float _RoughnessBrightness;
71 float _RoughnessMin;
72 float _RoughnessMax;
73
74
75 float3 RotateAround(float degree, float3 target)
76 {
77 float rad = degree * PI / 180;
78 float2x2 m_rotate = float2x2(cos(rad), -sin(rad),
79 sin(rad), cos(rad));
80 float2 dir_rotate = mul(m_rotate, target.xz);
81 target = float3(dir_rotate.x, target.y, dir_rotate.y);
82 return target;
83 }
84
85 inline float3 ACES_Tonemapping(float3 x)
86 {
87 float a = 2.51f;
88 float b = 0.03f;
89 float c = 2.43f;
90 float d = 0.59f;
91 float e = 0.14f;
92 float3 encode_color = saturate((x*(a*x + b)) / (x*(c*x + d) + e));
93 return encode_color;
94 };
95
96 v2f vert (appdata v)
97 {
98 v2f o;
99 o.pos = TransformObjectToHClip(v.vertex.xyz);
100 o.uv = v.texcoord * _NormalMap_ST.xy + _NormalMap_ST.zw;
101 o.pos_world = mul(unity_ObjectToWorld, v.vertex).xyz;
102 o.normal_world = normalize(mul(float4(v.normal, 0.0), unity_WorldToObject).xyz);
103 o.tangent_world = normalize(mul(unity_ObjectToWorld, float4(v.tangent.xyz, 0.0)).xyz);
104 o.binormal_world = normalize(cross(o.normal_world, o.tangent_world)) * v.tangent.w;
105 return o;
106 }
107
108 half4 frag (v2f i) : SV_Target
109 {
110 half3 normal_dir = normalize(i.normal_world);
111 half3 normaldata = UnpackNormal(SAMPLE_TEXTURE2D(_NormalMap,sampler_NormalMap,i.uv));
112 normaldata.xy = normaldata.xy* _NormalIntensity;
113 half3 tangent_dir = normalize(i.tangent_world);
114 half3 binormal_dir = normalize(i.binormal_world);
115 normal_dir = normalize(tangent_dir * normaldata.x + binormal_dir * normaldata.y + normal_dir * normaldata.z);
116
117 half ao = SAMPLE_TEXTURE2D(_AOMap, sampler_AOMap, i.uv).r;
118 ao = lerp(1.0,ao, _AOAdjust);
119
120 half3 env_color = SampleSH(normal_dir);
121 half3 final_color = env_color * ao * _Tint.rgb * _Expose;
122
123 return float4(final_color,1.0);
124 }
125 ENDHLSL
126 }
127 }
128 FallBack "Hidden/Universal Render Pipeline/FallbackError"
129 }
效果如下：
转载请注明出处：https://www.cnblogs.com/jietian331/p/17027769.html
标签：normal,float,Shader,custom,Unity,SH,world,dir,float3 From： https://www.cnblogs.com/jietian331/p/17027769.html