/*
Author:gzg
Date:2019-09-09
Desc:这个Shader要做一些操作,把图片的alpha通道写到帧缓中,主要是为了配合BloomCmd的处理
*/
Shader "Hidden/Ares/PostEffect/OnlyWriteAlpha"
{
	Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100
		ColorMask A
		
        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

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

            struct v2f
            {
				float4 vertex : SV_POSITION;
                float2 uv : TEXCOORD0;      
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);                
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                // sample the texture
                fixed4 col = tex2D(_MainTex, i.uv);  
                return col;
            }
            ENDCG
        }
    }
}