Shader实现新手指引挖空圆形和矩形

这个是参考这个做的：https://blog.csdn.net/tracyzly/article/details/80279692

Shader "UI/ImageWithHole"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _TintColor ("Tint", Color) = (1,1,1,1)

        _StencilComp ("Stencil Comparison", Float) = 8
        _Stencil ("Stencil ID", Float) = 0
        _StencilOp ("Stencil Operation", Float) = 0
        _StencilWriteMask ("Stencil Write Mask", Float) = 255
        _StencilReadMask ("Stencil Read Mask", Float) = 255

        [KeywordEnum(ROUND, RECTANGLE, NULL)] _MaskMode("Mask mode", Float) = 0
        _Center("Center", vector) = (0, 0, 0, 0)
        _Radius("Radius", Range(0,1000)) = 100 // 圆半径
        _RectangleSize("Rectangle Size", vector) = (0, 0, 0, 0) // 矩形边长
        _TransitionRange("Transition Range", Range(0, 100)) = 10
    }

    SubShader
    {
        Tags
        {
            "Queue"="Transparent"
            "IgnoreProjector"="True"
            "RenderType"="Transparent"
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }

        Stencil
        {
            Ref [_Stencil]
            Comp [_StencilComp]
            Pass [_StencilOp]
            ReadMask [_StencilReadMask]
            WriteMask [_StencilWriteMask]
        }

        Cull Off
        Lighting Off
        ZWrite Off
        Blend SrcAlpha OneMinusSrcAlpha
        ColorMask RGBA

        Pass
        {
            Name "Default"
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma target 2.0

            #include "UnityCG.cginc"
            #include "UnityUI.cginc"

            #pragma multi_compile __ UNITY_UI_CLIP_RECT
            #pragma multi_compile __ UNITY_UI_ALPHACLIP
            #pragma multi_compile _MASKMODE_ROUND _MASKMODE_RECTANGLE _MASKMODE_NULL

            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                float2 texcoord  : TEXCOORD0;
                float4 worldPosition : TEXCOORD1;
                UNITY_VERTEX_OUTPUT_STEREO
            };

            fixed4 _TintColor;
            fixed4 _TextureSampleAdd;
            float4 _ClipRect;
            float2 _Center;
            half _Radius;
            float2 _RectangleSize;
            half _TransitionRange;

            v2f vert(appdata_t v)
            {
                v2f OUT;
                UNITY_SETUP_INSTANCE_ID(v);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(OUT);
                OUT.worldPosition = v.vertex;
                OUT.vertex = UnityObjectToClipPos(OUT.worldPosition);

                OUT.texcoord = v.texcoord;

                OUT.color = v.color * _TintColor;
                return OUT;
            }

            sampler2D _MainTex;

            fixed4 frag(v2f i) : SV_Target
            {
                half4 color = (tex2D(_MainTex, i.texcoord) + _TextureSampleAdd) * i.color;

                #ifdef UNITY_UI_CLIP_RECT
                color.a *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);
                #endif

                #ifdef UNITY_UI_ALPHACLIP
                clip (color.a - 0.001);
                #endif

                #ifdef _MASKMODE_ROUND
                    // 计算片元世界坐标和目标中心位置的距离
                    half dis = distance(i.worldPosition.xy, _Center.xy);
                    // 过滤掉距离小于（半径-过渡范围）的片元
                    clip(dis - (_Radius - _TransitionRange));
                    // 是否在圆里面
                    int inside = step(dis, _Radius);
                    // 计算过渡范围内的alpha值
                    color.a *= (1 - inside) + inside * (dis - (_Radius - _TransitionRange)) / _TransitionRange;
                #elif _MASKMODE_RECTANGLE
                    // 计算片元世界坐标和目标中心位置的距离
                    half disX = distance(i.worldPosition.x, _Center.x);
                    half disY = distance(i.worldPosition.y, _Center.y);
                    // x决定像素点应该去掉返回1，不去掉返回0
                    int clipX = step(disX, _RectangleSize.x-_TransitionRange);
                    int clipY = step(disY, _RectangleSize.y-_TransitionRange);
                    clip(disX - (_RectangleSize.x -_TransitionRange) * clipY);
                    clip(disY - (_RectangleSize.y -_TransitionRange) * clipX);

                    // x在范围内返回1，不在范围内返回0
                    int insideX = step(disX, _RectangleSize.x);
                    int insideY = step(disY, _RectangleSize.y);
                    half alphaX= (1 - insideX) + insideX * (disX - (_RectangleSize.x - _TransitionRange)) / _TransitionRange;
                    half alphaY= (1 - insideY) + insideY * (disY - (_RectangleSize.y - _TransitionRange)) / _TransitionRange;
                    color.a *= max(alphaX, alphaY);
                #endif
                return color;
            }
        ENDCG
        }
    }
}