Shader "UI/CircleDissolveEffect"
{
    Properties
    {
        _MainTex("Main Texture", 2D) = "white" {}
        _Center("Dissolve Center", Vector) = (0.5, 0.5, 0, 0)
        _Radius("Dissolve Radius", Range(0, 1)) = 0.5
        _EdgeWidth("Edge Width", Range(0, 0.1)) = 0.05
        _EdgeColor("Edge Color", Color) = (1,1,1,1)
        _AspectRatio("Aspect Ratio", Float) = 1.0
    }

        SubShader
        {
            Tags {"Queue" = "Transparent" "RenderType" = "Transparent"}
            LOD 100

            Blend SrcAlpha OneMinusSrcAlpha
            Cull Off
            ZWrite Off

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

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

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

                sampler2D _MainTex;
                float2 _Center;
                float _Radius;
                float _EdgeWidth;
                fixed4 _EdgeColor;
                float _AspectRatio;

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

                fixed4 frag(v2f i) : SV_Target
                {
                    float2 uv = i.uv;
                    fixed4 mainColor = tex2D(_MainTex, uv);

                    // 调整 UV 坐标的比例，使得圆形遮罩在非方形图片上保持为圆形
                    float2 adjustedUV = uv;
                    adjustedUV.x = (uv.x - _Center.x) * _AspectRatio + _Center.x;

                    // 计算当前像素到遮罩中心的距离
                    float dist = distance(adjustedUV, _Center);

                    // 根据距离和半径计算溶解值
                    float dissolveThreshold = smoothstep(_Radius - _EdgeWidth, _Radius, dist);

                    // 混合边缘颜色
                    fixed4 edgeColor = _EdgeColor * (1.0 - dissolveThreshold);

                    // 应用溶解效果
                    return lerp(edgeColor, mainColor, dissolveThreshold) * mainColor.a;
                }
                ENDCG
            }
        }

            FallBack "Diffuse"
}