// Upgrade NOTE: replaced '_World2Object' with 'unity_WorldToObject'
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
Shader "My/Shader_diffuse_Lambert"
{
    Properties
    {
        _Diffuse("漫反射",color) = (1.0,1.0,1.0,1.0)
    }


        SubShader
    {


        Pass
    {
        Tags{ "LightMode" = "ForwardBase" }

        CGPROGRAM
#pragma vertex vert
#pragma fragment frag

#include "Lighting.cginc"

        fixed4 _Diffuse;  //颜色属性范围是0~1 所以可以使用 fixed 来存放

    struct a2v {
        float4 vertex:POSITION;
        float3 normal:NORMAL;
    };



    struct v2f {
        float4 pos: SV_POSITION;
        fixed3 worldNormal : TEXCOORD0;
    };

    v2f vert(a2v v)
    {
        v2f o;
        o.pos = UnityObjectToClipPos(v.vertex);
        o.worldNormal = normalize(mul(v.normal, (float3x3)unity_WorldToObject));//顶点的世界坐标系法线

        return o;
    }

    fixed4 frag(v2f i) : SV_Target
    {
        fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.rgb;
    fixed3 worldNormal = normalize(i.worldNormal);
    fixed3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz);

    fixed halFLambert = dot(worldNormal, worldLightDir) *0.5 + 0.5;

    fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * halFLambert;
    fixed3 color = ambient + diffuse;

    return fixed4(color, 1.0);
    }

        ENDCG
    }
    }

        Fallback "Diffuse"
}

三个光谱效果对比.png

• 左 ：顶点着色器计算光谱 点击跳转详情
• 中 ：片元着色器计算光谱 点击跳转详情
• 右 ：半兰伯特，避免全黑表面