Shader "Hidden/SimpleGaussianBlur"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {} _BlurSize ("Blur Size", Float) = 1
    }
    SubShader
    {
        Tags
        {
            "RenderType"="Opaque"
        }
        Pass
        {
            ZTest Always Cull Off ZWrite Off
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            sampler2D _MainTex;
            float4 _MainTex_TexelSize;
            float _BlurSize;
            float2 _Direction; // (1,0)=horizontal, (0,1)=vertical

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

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

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

            fixed4 frag(v2f i):SV_Target
            {
                float2 texel = _MainTex_TexelSize.xy * _BlurSize * _Direction;

                // 9-tap weights（近似高斯）
                fixed4 c = tex2D(_MainTex, i.uv) * 0.227027f;
                c += tex2D(_MainTex, i.uv + texel * 1.384615f) * 0.316216f;
                c += tex2D(_MainTex, i.uv - texel * 1.384615f) * 0.316216f;
                c += tex2D(_MainTex, i.uv + texel * 3.230769f) * 0.070270f;
                c += tex2D(_MainTex, i.uv - texel * 3.230769f) * 0.070270f;
                return c;
            }
            ENDHLSL
        }
    }
}