Shader "Unlit/Matcap"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Matcap("Mapcap",2D) = "white"{}
        _MatcapPower("MatcapPower", Float) = 2
        _MatcapAdd("MapcapAdd",2D) = "white"{}
        _MatcapAddPower("MatcapAddPower", Float) = 2
        _RampTex("RampTex",2D) = "white"{}
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM 
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
                float3 normal :NORMAL;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
                float3 normal_world:TEXCOORD1;
                float3 pos_world:TEXCOORD2;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            sampler2D _Matcap;
            float _MatcapPower;
            sampler2D _MatcapAdd;
            float _MatcapAddPower;
            sampler2D _RampTex;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.normal_world = mul(float4(v.normal,0), unity_WorldToObject);
                o.pos_world = mul(unity_ObjectToWorld, v.vertex).xyz;
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                //主贴图
                float4 tex_color = tex2D(_MainTex,i.uv);

                //Matcap 计算采样的uv  使用
                float3 normal_world = normalize(i.normal_world);
                float3 normal_view = mul(UNITY_MATRIX_V, float4(normal_world,0));
                float2 map_cap_uv = (normal_view.xy + float2(1,1)) * 0.5;
                float4 mapcap_color = tex2D(_Matcap, map_cap_uv) * _MatcapPower;

                //叠加的 Matcap
                float4 matcap_add = tex2D(_MatcapAdd, map_cap_uv) * _MatcapAddPower; 

                //用菲涅尔来采样渐变图 1-0
                float3 view_world = normalize(_WorldSpaceCameraPos.xyz - i.pos_world);
                half NdotV = saturate(dot(normal_world,view_world));
                half sample = 1 - NdotV;
                float4 ramp_color = tex2D(_RampTex, float2(sample,sample));

                float4 final_color = mapcap_color * tex_color * ramp_color + matcap_add;
                return final_color;
            }
            ENDCG
        }
    }
}

Matcap贴图