眼睛部分单独作为一个材质球，准备一张睁眼一张闭眼的贴图，在shader中自动切换贴图，实现眨眼效果 

Shader "MyShader/ChangeEmoji"
{
    Properties 
	{
        _MainTex ("Open Eye Tex", 2D) = "white" {}
        _TargetTex ("Close Eye Tex", 2D) = "white" {}
		_BlinkSpeed("Blink Speed",float) = 3
		_BlinkRatio("Blink Ratio",float) = 0.05
    }
    SubShader 
	{
        Tags
        {
			//渲染队列
            "Queue" = "Transparent"
            "IgnoreProjector" = "True"
            "RenderType" = "TransparentCutout"
        }
        Pass
        {
            //光照模式
            Tags { "LightMode"="ForwardBase" }

			//关闭深度写入
			ZWrite Off
			Blend SrcAlpha OneMinusSrcAlpha

            CGPROGRAM

            //定义顶点/片元着色器代码
			#pragma vertex vert
			#pragma fragment frag
            //包含内置文件
			#include "Lighting.cginc"

            sampler2D _MainTex;
            float4 _MainTex_ST;
            sampler2D _TargetTex;
            float4 _TargetTex_ST;
            float _BlinkSpeed;
            float _BlinkRatio;

            //定义顶点着色器的输入
            struct a2v 
            {
				float4 vertex : POSITION;
				float3 normal : NORMAL;
				float4 texcoord : TEXCOORD0;
			};
            //定义顶点着色器的输出、片元着色器的输入
			struct v2f 
            {
				float4 pos : SV_POSITION;
				float3 worldNormal : TEXCOORD0;
				float3 worldPos : TEXCOORD1;
				float2 uv : TEXCOORD2;
			};

            v2f vert(a2v v) 
            {
				v2f o;
				o.pos = UnityObjectToClipPos(v.vertex);
				o.worldNormal = UnityObjectToWorldNormal(v.normal);
				o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
                //无论现实哪张贴图，都使用贴图_MainTex的uv坐标
				o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
				return o;
			}

			fixed4 frag(v2f i) : SV_Target 
            {
				//tex2D函数：对纹理进行采样，tex2D(采样的纹理, 纹理坐标)
                //step函数，step(a, x) 等同于 (x >= a) ? 1 : 0

                cos函数计算眨眼时间周期
				//float cosValue = (cos(_Time.y*_BlinkSpeed)+1)*0.5;
                //int stepValue = step(_BlinkRatio,cosValue);
                //return tex2D(_MainTex, i.uv) * stepValue + tex2D(_TargetTex, i.uv) * (1-stepValue);

                //_Time取余计算眨眼时间周期
                //float timer = (_Time.y % _BlinkPeriod)
                int stepValue = step(_BlinkTime,(_Time.y % _BlinkPeriod));
                return tex2D(_MainTex, i.uv) * stepValue + tex2D(_TargetTex, i.uv) * (1-stepValue);
			}

            ENDCG
        }
    }
    FallBack "Diffuse"
}