漫反射的计算公式：

float brigthness=dot(normal,lightDir)------法线和光线方向得到亮度

float3 pixelColor=brightness*lightColor*surfaceColor------表面像素最终的颜色

 

1、定义漫反射的变量，法线向量

            struct appdata
            {
                float4 vertex : POSITION;
                float3 normal:Normal;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float3 worldNormal : TEXCOORD1;
            };

一个是对象空间坐标的法向量，另一个是世界空间坐标的法向量；

2、将对象空间坐标变换到世界空间坐标

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                float3 worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldNormal = worldNormal;
                return o;
            }

3、片元着色器将其进行计算，输出最终的颜色

            fixed4 frag (v2f i) : SV_Target
            {
                float3 normalDirection = normalize(i.worldNormal);
                float nl = max(0.0, dot(normalDirection, _WorldSpaceLightPos0.xyz));
                float4 diffuseTerm = nl *_Color;

                return diffuseTerm;
            }

 

当然还可以添加贴图

完整代码如下：

Shader "Unlit/DiffuseShader"
{
    Properties
    {
        _Color("Color",Color) = (1,0,0,1)
        _DiffuseTex("Texture",2D) = "white"{}
        _Ambient("Ambient",Range(0,1))=0.25

    }

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

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"


            fixed4 _Color;
            sampler2D _DiffuseTex;
            float4 _DiffuseTex_ST;
            float _Ambient;


            struct appdata
            {
                float4 vertex : POSITION;
                float3 normal:Normal;
                float2 UV:TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float3 worldNormal : TEXCOORD1;
                float2 UV:TEXCOORD0;
            };

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                float3 worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldNormal = worldNormal;
                o.UV = TRANSFORM_TEX(v.UV, _DiffuseTex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                float3 normalDirection = normalize(i.worldNormal);
                float4 tex = tex2D(_DiffuseTex, i.UV);
                float nl = max(_Ambient, dot(normalDirection, _WorldSpaceLightPos0.xyz));
                float4 diffuseTerm = nl * tex*_Color;

                return diffuseTerm;
            }
            ENDCG
        }
    }
}