Light Probe（光照探针）

什么是Probe Lighting(探测照明)？

Spherical Harmonic Lighting（球谐光照）

Unity 中的 Light Probe

代码实现

// SH lighting environment    half4 unity_SHAr;    half4 unity_SHAg;    half4 unity_SHAb;    half4 unity_SHBr;    half4 unity_SHBg;    half4 unity_SHBb;    half4 unity_SHC;

// normal should be normalized, w=1.0half3SHEvalLinearL0L1 (half4 normal){    half3 x;// Linear (L1) + constant (L0) polynomial terms    x.r =dot(unity_SHAr,normal);    x.g =dot(unity_SHAg,normal);    x.b =dot(unity_SHAb,normal);return x;}

// normal should be normalized, w=1.0half3SHEvalLinearL2 (half4 normal){    half3 x1, x2;// 4 of the quadratic (L2) polynomials    half4 vB = normal.xyzz * normal.yzzx;    x1.r =dot(unity_SHBr,vB);    x1.g =dot(unity_SHBg,vB);    x1.b =dot(unity_SHBb,vB);// Final (5th) quadratic (L2) polynomial    half vC = normal.x*normal.x - normal.y*normal.y;    x2 = unity_SHC.rgb * vC;return x1 + x2;}

// normal should be normalized, w=1.0// output in active color spacehalf3ShadeSH9 (half4 normal){// Linear + constant polynomial terms    half3 res =SHEvalLinearL0L1 (normal);// Quadratic polynomials    res +=SHEvalLinearL2 (normal);#ifdef UNITY_COLORSPACE_GAMMA        res =LinearToGammaSpace (res);#endifreturn res;}

unity内置Light Probes的调用

fixed3 SHLighting : COLOR;

float3 worldNormal = mul((float3x3)_Object2World, v.normal);//获得世界坐标中的normalo.SHLighting= ShadeSH9(float4(worldNormal,1)) ;

Shader"Custom/TextureLM"{Properties{_Color("Color",Color) = (0,0,0,0)_SHLightingScale("LightProbe influence scale",float) =1}SubShader{Pass{Tags{"Queue"="Geometry""LightMode"="ForwardBase""RenderType"="Opaque"}CGPROGRAM#pragma vertex vert#pragma fragment frag#pragma multi_compile_fog#include"UnityCG.cginc"structv2f{float4 vertex : SV_POSITION;fixed3 SHLighting : COLOR;};float _SHLightingScale;float4 _Color;v2fvert(appdata_base v){v2f o;o.vertex =UnityObjectToClipPos(v.vertex);float3 worldNormal =mul((float3x3)unity_ObjectToWorld, v.normal);o.SHLighting =ShadeSH9(float4(worldNormal,1));return o;}fixed4frag(v2f i) : SV_Target{fixed4 col = _Color;col.rgb *= i.SHLighting;return col * _SHLightingScale;}ENDCG}}}