diffuse=Kd*_LightColor0*max(N·L,0)
Kd–環境光顏色、頂點顏色、點光源的距離衰減
_LightColor0–光源顏色
N·L–入射光向量 · 頂點法向量

Shader "Custom/MyDiffuse_Vertex"
{
    Properties
    {
        _MainTex("Texture", 2D) = "white" {}
        _Bright("Bright",Float)=2
    }

    SubShader
    {
        Tags{ "RenderType" = "Opaque"
 
 }

        Pass
        {
            Tags{ "LightMode" = "ForwardBase" }
            //處理平行光
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
            #include "Lighting.cginc"

            uniform sampler2D _MainTex;
            uniform float
 
 _Bright;
            struct appdata
            {
                float4 vertex:POSITION;
                float2 texcoord:TEXCOORD0;
                float3 normal:NORMAL;
            };


            struct v2f
            {
                float4 pos:SV_POSITION;
                float2 uv:TEXCOORD0;
                fixed4 color
 
 : COLOR;
            };


            v2f vert(in appdata v)
            {
                //_LightColor0 ：光的顏色
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex); //  頂點變換到裁剪空間
                o.uv = v.texcoord;
                float3 N = normalize(mul((float3x3)unity_ObjectToWorld, v.normal));//法線
                float3 L;//入射光方向
                float atten;//點光源的距離衰減係數
                if (_WorldSpaceLightPos0.w == 0)//_WorldSpaceLightPos0:平行光: (world space direction, 0)；
                {
                    L = normalize(_WorldSpaceLightPos0);
                    atten = 1;
                }
                else //_WorldSpaceLightPos0: 其他光: (world space position, 1).
                {
                    float3 light2Vertex = _WorldSpaceLightPos0 - mul(unity_ObjectToWorld, v.vertex);
                    L = normalize(light2Vertex);
                    float Length = length(light2Vertex);
                    atten = 1 / Length;
                }
                float Kd = UNITY_LIGHTMODEL_AMBIENT*atten*_Bright;
                //計算入射光和法線的夾角的餘弦值，並剔除小於零的值（小於0的值相當於從物體的背面向物體表面照射，沒有物理意義）
                float cos = max(dot(N, L),0);
                fixed4 difColor = Kd*_LightColor0 *cos;//漫反射光的顏色
                o.color = difColor;
                return o;
            }

            fixed4 frag(v2f i) :SV_Target 
            {
                fixed4 col;
                col = tex2D(_MainTex, i.uv);
                col *= i.color;
                return col;
            }
            ENDCG
        }

        Pass
        {
            Tags{ "LightMode" = "ForwardAdd" }
            //處理點光源
            Blend one one   //**著重注意
            //與前一個Pass 的顏色1：1混合 
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
            #include "Lighting.cginc"

            uniform sampler2D _MainTex;
            uniform float _Bright;
            struct appdata
            {
                float4 vertex:POSITION;
                float2 texcoord:TEXCOORD0;
                float3 normal:NORMAL;
            };


            struct v2f
            {
                float4 pos:SV_POSITION;
                float2 uv:TEXCOORD0;
                fixed4 color : COLOR;
            };


            v2f vert(in appdata v)
            {
                //_LightColor0 ：光的顏色
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex); //  頂點變換到裁剪空間
                o.uv = v.texcoord;
                float3 N = normalize(mul((float3x3)unity_ObjectToWorld, v.normal));//法線
                float3 L;//入射光方向
                float atten;//點光源的距離衰減係數
                if (_WorldSpaceLightPos0.w == 0)//_WorldSpaceLightPos0:平行光: (world space direction, 0)；
                {
                    L = normalize(_WorldSpaceLightPos0);
                    atten = 1;
                }
                else //_WorldSpaceLightPos0: 其他光: (world space position, 1).
                {
                    float3 light2Vertex = _WorldSpaceLightPos0 - mul(unity_ObjectToWorld, v.vertex);
                    L = normalize(light2Vertex);
                    float Length = length(light2Vertex);
                    atten = 1 / Length;
                }
                float Kd = UNITY_LIGHTMODEL_AMBIENT*atten*_Bright;
                //計算入射光和法線的夾角的餘弦值，並剔除小於零的值（小於0的值相當於從物體的背面向物體表面照射，沒有物理意義）
                float cos = max(dot(N, L),0);
                fixed4 difColor = Kd*_LightColor0 *cos;//漫反射光的顏色
                o.color = difColor;
                return o;
            }

            fixed4 frag(v2f i) :SV_Target
            {
                fixed4 col;
                col = tex2D(_MainTex, i.uv);
                col *= i.color;
                return col;
            }
            ENDCG
        }

    }
}