Hole

Shader "Hole" {
    Properties {
        _MainTex ("Base (RGB)", 2D) = "white" {}
        _LeftEye ("Left Eye",Vector) = (0,0,0,0)
        _LeftOval("Left Eye Oval", float)= 1
    }
    Category {
        Blend SrcAlpha OneMinusSrcAlpha
        Tags {Queue = Transparent}
        SubShader {
            Pass{
            CGPROGRAM
            #pragma vertex vert_img
            #pragma fragment frag
            #pragma target 3.0
            #include "UnityCG.cginc"
                sampler2D _MainTex;
                float4 _LeftEye;
                float _LeftOval;

                float4 frag(v2f_img i) : COLOR {
                    float4 c = tex2D (_MainTex, i.uv);//samples the texture
                    c.a = clamp(distance(float2(i.uv.x,(_LeftEye.y-i.uv.y)*_LeftOval+i.uv.y), _LeftEye)*_LeftEye.z+_LeftEye.w,0,1);
                    return c;
                }
            ENDCG
            }
        }
    }
    FallBack "Diffuse"
}