效果：

代码实现： 

Shader "MyShader/Sim"
{
   Properties
   {
        _MainTex("主贴图",2D)="white"{}
        _MainColor("主贴图颜色",color)=(1,1,1,1)
        _InnerSimPower("内描边强度",Range(-1.0,3.0))=0.0
        _InnerSimColor("内描边颜色",color)=(1,1,1,1)
        _OutSimPower("外描边强度",Range(0.0,5.0))=1.0
        _OutSimColor("外描边颜色",color)=(1,1,1,1)
        _RimIntensity("描边颜色插值",Range(0.0,1.0))=0
   }
   SubShader
   {
        Pass
        {
            ColorMask 0
            ZWrite On
        }

        Tags{"RenderType"="Transparent"  "Queue"="Transparent"}

        Pass
        {
            Blend SrcAlpha One
            ZWrite Off
            CGPROGRAM
            #pragma vertex vert 
            #pragma fragment frag 
            #include "UnityCG.cginc"

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float _InnerSimPower;
            float _OutSimPower;
            fixed3 _InnerSimColor;
            fixed3 _OutSimColor;
            fixed3 _MainColor;
            float _RimIntensity;

            struct vertexInput
            {
                float4 vertex:POSITION;
                float3 normal:NORMAL;
                float4 texcoord:TEXCOORD0;
            };

            struct  vertexOutput
            {
                float4 pos:SV_POSITION;
                float3 worldNormal:TEXCOORD0;
                float3 worldPos:TEXCOORD1;
                float2 uv:TEXCOORD2;
            };

            vertexOutput vert(vertexInput v)
            {
                vertexOutput o = (vertexOutput)0;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldPos = mul(unity_ObjectToWorld,v.vertex).xyz;
                o.uv = TRANSFORM_TEX(v.texcoord,_MainTex);
                return o;
            }

            float4 frag(vertexOutput i):SV_TARGET
            {
                half3 worldNormal = normalize(i.worldNormal);
                half3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));
                half3 viewDir = normalize(UnityWorldSpaceViewDir(i.worldPos));

                float finnesl = smoothstep(_InnerSimPower,_OutSimPower,1-saturate(dot(worldNormal,viewDir)));

                fixed3 abledo = tex2D(_MainTex,i.uv).rgb*_MainColor.rgb;
                fixed3 color = finnesl*lerp(_InnerSimColor.rgb,_OutSimColor.rgb,_RimIntensity)*abledo;

                return float4(color,finnesl);
            }
            ENDCG
        }
   }
}