//以下是各種光照模型（Lambert、Phong、BlinnPhong、Gourand）的Shader程式碼，在Unity裡建立一個Material後可以選擇使用，各行程式碼都有註釋，不再詳細解釋了。

Shader "MyShader/BaseShader"
{
//包含Lambert、Phone、Blin-Phong模型
Properties
{//定義屬性
_Diffuse("Diffuse",Color) = (1,1,1,1)
_Specular("Specular",Color) = (1,1,1,1)
_Gloss("Gloss",Range(5,255)) = 5
[Toggle(_Phong)] _Phong("Phong",float) = 1
[Toggle(BlinnPhong)] _BlinnPhong("BlinnPhong",float) = 1
_MainTex ("Texture", 2D) = "white" {}
}

SubShader
{
Tags { "RenderType"="Opaque" "LightMode"="ForwardBase"} //定義Tag
//LOD 100

Pass
{
CGPROGRAM
#include "UnityCG.cginc" //庫函式
#include "Lighting.cginc"
//定義觸發器，改變光照模型
#pragma shader_feature _PHONG
#pragma shader_feature _BLINNPHONG
#pragma shader_feature _LAMBERT
#pragma shader_feature _GOURAND

#pragma vertex vert //頂點著色器名稱
#pragma fragment frag //片元著色器名稱

float4 _Diffuse; //全域性引數，漫反射、高光顏色、高光引數
float4 _Specular;
float _Gloss;

struct a2v
{//應用傳入頂點著色器的變數
float4 vertex : POSITION;
float3 normal :NORMAL;
float2 uv : TEXCOORD0;
};

struct v2f
{
float2 uv : TEXCOORD0;
float4 vertex : SV_POSITION;
float3 worldNormal: NORMAL;
float3 worldPos: TEXCOORD1;
float3 color: TEXCOORD2;
};

sampler2D _MainTex;
float4 _MainTex_ST;

v2f vert (a2v v)
{//頂點著色器
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex); //頂點空間到裁剪空間
//o.worldNormal = normalize(mul(v.normal,(float 3x3) unity_worldTo));
o.worldNormal = UnityObjectToWorldNormal(v.normal); //法線轉換到世界空間
o.worldPos = mul(unity_ObjectToWorld,v.vertex).xyz; //頂點位置轉換到世界空間

o.uv = TRANSFORM_TEX(v.uv, _MainTex);
#if defined(_GOURAND)
float3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * _Diffuse; //環境光
float3 worldLight = normalize(_WorldSpaceLightPos0.xyz); //歸一化光方向
float3 worldNormal = normalize(o.worldNormal); //歸一化worldNormal
float NdotL = max(0, dot(worldLight, worldNormal)); //法線和光線的點積，即餘弦值
float3 diffuse = _LightColor0.rgb * _Diffuse.rgb * NdotL; //計算漫反射Lambert
float3 viewDir = normalize(_WorldSpaceCameraPos.xyz - o.worldPos.xyz); //視角方向
float3 reflectDir = normalize(reflect(-worldLight,worldNormal)); //計算反射方向，worldLight表示入射光方向
float VdotR = max(0, dot(reflectDir, viewDir)); //反射光方向與觀察方向的夾角，點積結果為夾角的餘弦值
float3 specular = _LightColor0.rgb * _Specular.rgb * pow(VdotR, _Gloss); //高光值
o.color = diffuse + ambient + specular; //Gourand模型最後輸出的顏色值
#endif
return o;
}

fixed4 frag (v2f i) : SV_Target
{//片元著色器
// sample the texture
//fixed4 col = tex2D(_MainTex, i.uv);
float3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * _Diffuse; //環境光
float3 worldLight = normalize(_WorldSpaceLightPos0.xyz); //歸一化光方向
float3 worldNormal = normalize(i.worldNormal); //歸一化worldNormal
float NdotL = max(0, dot(worldNormal,worldLight)); //計算漫反射Lambert公式
fixed4 renderTex = tex2D(_MainTex, i.uv);

float3 diffuse = _LightColor0.rgb * _Diffuse.rgb * NdotL; //計算Diffuse光
float3 specular; //儲存高光值
float3 color; //儲存最終顏色值

float3 viewDir = normalize(_WorldSpaceCameraPos.xyz - i.worldPos.xyz); //歸一化視方向
#if defined(_LAMBERT)
color = diffuse; //Lambert模型
#endif

//#if defined(_PHONG)
//Phong模型計算
float3 reflectDir = normalize(reflect(-worldLight,worldNormal)); //計算反射方向，worldLight表示入射光方向
float VdotR = max(0, dot(viewDir,reflectDir)); //反射光方向與觀察方向的夾角，dot(ViewDir,ReflectDir)
specular = _LightColor0.rgb * _Specular.rgb * pow(VdotR, _Gloss); //計算高光反射
color = ambient + diffuse + specular;
//#endif

#if defined(_BLINNPHONG)
//BlinnPhong模型計算
float3 halfDir = (worldLight +viewDir); //計算半形向量，光線方向+視方向的結果歸一化
float NdotH = saturate(dot(halfDir,worldNormal)); //半形向量與法線方向的點積，結果歸一化
specular = _LightColor0.rgb * _Specular.rgb * pow(NdotH, _Gloss); //計算BlinnPhong的高光值
color = ambient + diffuse + specular;
#endif

#if defined(_GOURAND)
color = i.color; //直接使用頂點著色器中計算出來的顏色值
#endif
color = color * renderTex.rgb;
return fixed4(color,1.0);
}
ENDCG
}
}
}