Question 2D circle hole with antialiasing on object

I'd like to add a hole inside an empty object with sprites inside. This hole has a circle shape.

To achieve that, I added a shader to a material and the material to a Sprite Renderer component to the empty object.

Here is my Shader :

Code (CSharp):

1. Shader "Sprite/XRay Effect"
2. {
3.     Properties
4.     {
5.         _MainTex ("Base (RGB)", 2D) = "white" {}
6.         _ObjPos ("Object Position", Vector) = (1,1,1,1)
7.         _Cutoff ("Alpha cutoff", Range(0,1)) = 0.5
8.         _Radius ("Hole Radius", Range(0.1,10)) = 2
9.     }
10.  
11.     SubShader
12.     {
13.         Pass
14.         {
15.             Cull Off
16.  
17.             CGPROGRAM
18.  
19.             #pragma vertex vert
20.             #pragma fragment frag
21.  
22.             uniform sampler2D _MainTex;
23.             float _Radius;
24.             float4 _ObjPos;
25.  
26.             struct vertexInput {
27.                 float4 vertex : POSITION;
28.                 float4 texcoord : TEXCOORD0;
29.             };
30.             struct vertexOutput {
31.                 float4 pos : SV_POSITION;
32.                 float4 worldPos : POSITION1;
33.                 float4 tex : TEXCOORD0;
34.             };
35.  
36.             vertexOutput vert(vertexInput input)
37.             {
38.                 vertexOutput output;
39.  
40.                 output.tex = input.texcoord;
41.                 output.pos = UnityObjectToClipPos(input.vertex);
42.                 output.worldPos = mul(input.vertex, unity_ObjectToWorld);
43.                 return output;
44.             }
45.  
46.             float4 frag(vertexOutput input) : COLOR
47.             {
48.                 float4 textureColor = tex2D(_MainTex, input.tex.xy);
49.                 float dis = distance(input.worldPos.xyz, _ObjPos);
50.  
51.                 if (dis > _Radius)
52.                 {
53.                     discard;
54.                 }
55.  
56.                 return textureColor;
57.             }
58.  
59.             ENDCG
60.         }
61.     }
62.  
63.     FallBack "Diffuse"
64. }

The problem with this method is that there is no antialiasing for the circle...

So I tried to add a Sprite mask to the empty object instead, but there is no antialiasing nether...

I think the shader is the good solution to achieve that but really don't know how!

Any help would be perfect!!!

 

The way to do that is to control opacity of pixels...

Outside of the radius, opacity is 1 Inside, it's 0. And between, I could use lerp and the distance to decrease opacity from 1 (outside) to 0 (inside) to add an antialiasing...

The problem is that in this function

Code (CSharp):

1. float4 frag(vertexOutput input) : COLOR
2.               {
3.                   float4 textureColor = tex2D(_MainTex, input.tex.xy);
4.                   float dis = distance(input.worldPos.xyz, _ObjPos);
5.  
6.                   if (dis > _Radius)
7.                   {
8.                       discard;
9.                   }
10.  
11.                   return textureColor;
12.               }

I can only define 'true' or 'false' (return or discard)

 

Finally I found it!!

I applied a material with a shader to the sprites of the object where I want to see the circle.

Here is my shader:

Code (CSharp):

1. Shader "Sprites/XRay Effect"
2. {
3.     Properties
4.     {
5.         [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
6.      
7.         _PlayerPos ("Player Position", Vector) = (0,0,0,0)
8.         _Radius ("Hole Radius", Range(0.1,100)) = 2
9.         _Border ("Border", Range(0.001,1)) = 0.05
10.     }
11.  
12.     SubShader
13.     {
14.         Tags
15.         {
16.             "Queue"="Transparent"
17.             "IgnoreProjector"="True"
18.             "RenderType"="Transparent"
19.             "PreviewType"="Plane"
20.             "CanUseSpriteAtlas"="True"
21.         }
22.      
23.         Cull Off
24.         Lighting Off
25.         ZWrite Off
26.         ZTest [unity_GUIZTestMode]
27.         Blend SrcAlpha OneMinusSrcAlpha
28.  
29.         Pass
30.         {
31.             CGPROGRAM
32.  
33.             #pragma vertex vert
34.             #pragma fragment frag
35.  
36.             #include "UnityCG.cginc"
37.             #include "UnityUI.cginc"
38.          
39.             struct vertexInput
40.             {
41.                 float4 vertex   : POSITION;
42.                 float4 color    : COLOR;
43.                 float2 texCoord : TEXCOORD0;
44.             };
45.  
46.             struct vertexOutput
47.             {
48.                 float4 vertex   : SV_POSITION;
49.                 fixed4 color    : COLOR;
50.                 half2 texCoord  : TEXCOORD0;
51.                 float3 worldPosition : TEXCOORD1;
52.             };
53.          
54.             sampler2D _MainTex;
55.          
56.             float4 _PlayerPos;
57.             float _Radius;
58.             float _Border;
59.  
60.             vertexOutput vert(vertexInput IN)
61.             {
62.                 vertexOutput OUT;
63.  
64.                 OUT.vertex = UnityObjectToClipPos(IN.vertex);
65.                 OUT.texCoord = IN.texCoord;
66.                 OUT.worldPosition = mul(unity_ObjectToWorld, IN.vertex);
67.                 OUT.color = IN.color;
68.  
69.                 return OUT;
70.             }
71.  
72.             fixed4 frag(vertexOutput IN) : SV_Target
73.             {
74.                 half4 color = tex2D(_MainTex, IN.texCoord) * IN.color;
75.              
76.                 // Adding the circle hole
77.                 float dis = distance(IN.worldPosition.xyz, _PlayerPos.xyz);
78.                 color.a = lerp(0, color.a, color.a * (dis - _Radius) / _Border);
79.  
80.                 return color;
81.             }
82.          
83.             ENDCG
84.         }
85.     }
86.     FallBack "UI/Default"
87. }

You can modify the part

lerp(0, color.a, color.a * (dis - _Radius) / _Border)

to your needs.