Unity3D ShaderLab 使用alpha参数创建透明效果

Shader "91YGame/AlphaTransparency" {
    Properties {
        _MainTex ("Base (RGB)", 2D) = "white" {}
        _TransVal("Transparency Value",Range(0.01,1))=0.5
    }
    SubShader {
        Tags { "RenderType"="Opaque" }
        LOD 200
        
        //alpha参数;
        CGPROGRAM
        #pragma surface surf Lambert alpha

        sampler2D _MainTex;
        float _TransVal;
        struct Input {
            float2 uv_MainTex;
        };

        void surf (Input IN, inout SurfaceOutput o) {
            half4 c = tex2D (_MainTex, IN.uv_MainTex);

            o.Albedo = c.rgb;
            o.Alpha =c.r*_TransVal;//c.g || c.b
        }
        ENDCG
    } 
    FallBack "Diffuse"
}