多光源 MultipleLight

使用2个Pass增加光照效果；

第一个Pass是基础光源，一般是第一个平行光；Tags{"LightMode" = "ForwardBase"}

第二个光源是增加的光源，一般是点光源；Tags{"LightMode" = "ForwardAdd"} Blend One One

混合：Blend

 

这里例如我们给一个模型贴一个材质，那么在某个点计算出来颜色值称为源，而该点之前累积的颜色值，叫目标。

 

语法

Blend SrcFactor DstFactor  SrcFactor是源系数，DstFactor是目标系数

最终颜色 = （Shader计算出的点颜色值 * 源系数）+（点累积颜色 * 目标系数）

 

属性（往SrcFactor，DstFactor 上填的值）

one                          1

zero                         0

SrcColor                         源的RGB值，例如（0.5,0.4,1）

SrcAlpha                         源的A值, 例如0.6

DstColor                   混合目标的RGB值例如（0.5，0.4,1）

DstAlpha                         混合目标的A值例如0.6

OneMinusSrcColor          (1,1,1) - SrcColor

OneMinusSrcAlpha          1- SrcAlpha

OneMinusDstColor          (1,1,1) - DstColor

OneMinusDstAlpha          1- DstAlpha

我们在Pass中计算光源时，需要注意，是平行光还是点光源：

                 float3 lightDirection;
                 float atten; 

                 if(_WorldSpaceLightPos0.w==0.0)//平行光
                 {
                     atten = 1.0;
                     lightDirection = normalize(_WorldSpaceLightPos0.xyz);
                 }
                 else
                 {
                     float3 fragmentToLightSource = _WorldSpaceLightPos0.xyz -i.posWorld.xyz;
                     float distance = length(fragmentToLightSource);
                     atten  = 1.0/distance;
                     lightDirection = normalize(fragmentToLightSource);
                 }

源代码：

 Shader "JQM/MultipleLight"
 {
     Properties
     {
         _Color("Color", color) = (1.0,1.0,1.0,1.0)
         _SpecColor("Specular Color", color) = (1.0,1.0,1.0,1.0)
         _Shininess("Shininess",float) =
         _RimColor("Rim Coloe Color", color) = (1.0,1.0,1.0,1.0)
         _RimPower("Rim Power",Range(0.1,10.0)) = 3.0

     }
     SubShader{
         Pass{

             Tags { "LightMode" = "ForwardBase"}

             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag

             //使用自定义变量
             uniform float4 _Color;
             uniform float4 _SpecColor;
             uniform float4 _RimColor;
             uniform float _Shininess;
             uniform float _RimPower;

             //使用Unity定义的变量
             uniform float4 _LightColor0;

             struct vertexInput{
                 float4 vertex:POSITION;
                 float3 normal:NORMAL;
             };

             struct vertexOutput{
                 float4 pos:SV_POSITION;
                 float4 posWorld:TEXCOORD0;
                 float3 normalDir:TEXCOORD1;
             };

             //顶点程序
             vertexOutput vert(vertexInput v)
             {
                 vertexOutput o;
                 o.posWorld = mul(_Object2World, v.vertex);
                 o.normalDir =  normalize( mul(float4(v.normal,0.0),_World2Object).xyz);
                 o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                 return o;
             }

             //片段程序
             float4 frag(vertexOutput i):COLOR
             {

                 float3 normalDirection = i.normalDir;
                 float3 viewDirection = normalize(_WorldSpaceCameraPos.xyz- i.posWorld.xyz);
                 float3 lightDirection;
                 float atten; 

                 if(_WorldSpaceLightPos0.w==0.0)//平行光
                 {
                     atten = 1.0;
                     lightDirection = normalize(_WorldSpaceLightPos0.xyz);
                 }
                 else
                 {
                     float3 fragmentToLightSource = _WorldSpaceLightPos0.xyz -i.posWorld.xyz;
                     float distance = length(fragmentToLightSource);
                     atten  = 1.0/distance;
                     lightDirection = normalize(fragmentToLightSource);
                 }

                 //灯光
                 float3 diffuseReflection = atten * _LightColor0.xyz *  saturate( dot(normalDirection,lightDirection));
                 float3 specularReflection = atten * _LightColor0.xyz * _SpecColor.rgb*saturate( dot(normalDirection,lightDirection))*pow(saturate(dot(reflect(-lightDirection,normalDirection),viewDirection)),_Shininess);

                 //Rim Light
                 float rim= -dot(normalize(viewDirection),normalDirection);
                 float3 rimLighting = atten * _LightColor0.xyz * _RimColor.rgb*saturate(dot(normalDirection,lightDirection))*pow(rim,_RimPower);
                 float3 lightFinal = rimLighting + diffuseReflection+specularReflection+UNITY_LIGHTMODEL_AMBIENT.xyz;
                 return float4(lightFinal*_Color.xyz,1.0);
             }

             ENDCG
         }

         Pass{

             Tags { "LightMode" = "ForwardAdd"}
             Blend  One One

             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag

             //使用自定义变量
             uniform float4 _Color;
             uniform float4 _SpecColor;
             uniform float4 _RimColor;
             uniform float _Shininess;
             uniform float _RimPower;

             //使用Unity定义的变量
             uniform float4 _LightColor0;

             struct vertexInput{
                 float4 vertex:POSITION;
                 float3 normal:NORMAL;
             };

             struct vertexOutput{
                 float4 pos:SV_POSITION;
                 float4 posWorld:TEXCOORD0;
                 float3 normalDir:TEXCOORD1;
             };

             //顶点程序
             vertexOutput vert(vertexInput v)
             {
                 vertexOutput o;
                 o.posWorld = mul(_Object2World, v.vertex);
                 o.normalDir =  normalize( mul(float4(v.normal,0.0),_World2Object).xyz);
                 o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                 return o;
             }

             //片段程序
             float4 frag(vertexOutput i):COLOR
             {

                 float3 normalDirection = i.normalDir;
                 float3 viewDirection = normalize(_WorldSpaceCameraPos.xyz- i.posWorld.xyz);
                 float3 lightDirection;
                 float atten; 

                 if(_WorldSpaceLightPos0.w==0.0)//平行光
                 {
                     atten = 1.0;
                     lightDirection = normalize(_WorldSpaceLightPos0.xyz);
                 }
                 else
                 {
                     float3 fragmentToLightSource = _WorldSpaceLightPos0.xyz -i.posWorld.xyz;
                     float distance = length(fragmentToLightSource);
                     atten = 1.0/distance;
                     lightDirection = normalize(fragmentToLightSource);
                 }

                 //灯光
                 float3 diffuseReflection = atten * _LightColor0.xyz *  saturate( dot(normalDirection,lightDirection));
                 float3 specularReflection = atten * _LightColor0.xyz * _SpecColor.rgb*saturate( dot(normalDirection,lightDirection))*pow(saturate(dot(reflect(-lightDirection,normalDirection),viewDirection)),_Shininess);

                 //Rim Light
                 float rim= -dot(normalize(viewDirection),normalDirection);
                 float3 rimLighting = atten * _LightColor0.xyz * _RimColor.rgb*saturate(dot(normalDirection,lightDirection))*pow(rim,_RimPower);
                 float3 lightFinal = rimLighting + diffuseReflection+specularReflection+UNITY_LIGHTMODEL_AMBIENT.xyz;
                 return float4(lightFinal*_Color.xyz,1.0);
             }

             ENDCG
         }
     }

 }