Shader "Custom/MultiImageBlend" {
    Properties {
        _MainTex ("Texture", 2D) = "white" {}
        _BlendColor ("Blend Color", Color) = (1,1,1,1)
        _BlendOffset ("Blend Offset", Vector) = (0,0,0,0)
    }
    
    SubShader {
        Tags { "Queue"="Transparent" }
        Blend SrcAlpha OneMinusSrcAlpha

        Pass {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

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

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

            sampler2D _MainTex;
            float4 _MainTex_ST;
            fixed4 _BlendColor;
            float2 _BlendOffset;

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

            fixed4 frag (v2f i) : SV_Target {
                // 计算偏移后的UV坐标
                float2 blendUV = i.uv - _BlendOffset;
                if (any(blendUV < 0) || any(blendUV > 1))
                    discard;
                
                fixed4 col = tex2D(_MainTex, blendUV) * _BlendColor;
                return col;
            }
            ENDCG
        }
    }
}