World position of fragment

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Hi, I am trying to get the world position of the fragment into my fragment shader so I can shape the output based on a formula but Im not sure how to retrieve the world position of the fragment correctly

//
Shader "Unlit/SGD"
{
    Properties
    {
        _HeadPos("HeadPos" ,Vector) = (0,0,0)
        _eyeToTarget("eyeToTarget" ,Vector) = (0,0,0)     
        _Eccentricity("Eccentricity" ,Float) = 0.0

        _Alpha("Alpha", Range(0,1)) = 0.095
        _FlickerFreq("FlickerFreq", Range(0,120)) = 10
    }
        SubShader
    {
        Tags {
            "RenderType" = "Transparent"
            "Queue" = "Transparent"
            }
       ZWrite Off
        Blend SrcAlpha OneMinusSrcAlpha

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag


            #include "UnityCG.cginc"

          
                float _Alpha;
                float _FlickerFreq;
               
                float3 _HeadPos;
                float3 _eyeToTarget;
                float _Eccentricity;
               

            struct MeshData
            {
                float4 vertex : POSITION;
              
            };

            struct Interpolators
            {
                float4 vertex : SV_POSITION;
                float3 worldPos : TEXCOORD0;
            };

           

            Interpolators vert(MeshData v)
            {
                Interpolators o;
                o.worldPos = mul(unity_ObjectToWorld, v.vertex);
                o.vertex = UnityObjectToClipPos(v.vertex);
               
                return o;
            }

            float4 SquareWave(float In) {
                return 1.0 - 2.0 * round(frac(In));
            }

            float IntensityStim(float3 HeadPos, float3 eyeToTarget, float Eccentricity, float3 fragPos) {
                return (acos(dot(eyeToTarget, (HeadPos - fragPos))) / ((0.0098 * radians(Eccentricity)) + radians(0.1009)));
            }

            float4 frag(Interpolators i) : SV_Target
            {

                float4 Col = SquareWave(_Time.y * _FlickerFreq);
                Col.a = _Alpha * IntensityStim(_HeadPos,_eyeToTarget,_Eccentricity,i.worldPos);
               return Col;
            }
            ENDCG
        }
    }
}

What you have there is already correct.