WorldPositionFromDepth thx d4rkpl4y3r and lox

WorldPositionFromDepth.shader

Shader "Unlit/GridAllocation"
{
    SubShader
    {
        Tags { "Queue" = "Overlay" }
        ZTest Always

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

            struct v2f
            {
                float4 vertex : SV_Position;
                float4 clipPos : TEXCOORD0;
                nointerpolation float4x4 inverseVP : IVP;
            };

            UNITY_DECLARE_DEPTH_TEXTURE(_CameraDepthTexture);

            float4x4 inverse(float4x4 mat)
            {
                float4x4 M=transpose(mat);
                float m01xy=M[0].x*M[1].y-M[0].y*M[1].x;
                float m01xz=M[0].x*M[1].z-M[0].z*M[1].x;
                float m01xw=M[0].x*M[1].w-M[0].w*M[1].x;
                float m01yz=M[0].y*M[1].z-M[0].z*M[1].y;
                float m01yw=M[0].y*M[1].w-M[0].w*M[1].y;
                float m01zw=M[0].z*M[1].w-M[0].w*M[1].z;
                float m23xy=M[2].x*M[3].y-M[2].y*M[3].x;
                float m23xz=M[2].x*M[3].z-M[2].z*M[3].x;
                float m23xw=M[2].x*M[3].w-M[2].w*M[3].x;
                float m23yz=M[2].y*M[3].z-M[2].z*M[3].y;
                float m23yw=M[2].y*M[3].w-M[2].w*M[3].y;
                float m23zw=M[2].z*M[3].w-M[2].w*M[3].z;
                float4 adjM0,adjM1,adjM2,adjM3;
                adjM0.x=+dot(M[1].yzw,float3(m23zw,-m23yw,m23yz));
                adjM0.y=-dot(M[0].yzw,float3(m23zw,-m23yw,m23yz));
                adjM0.z=+dot(M[3].yzw,float3(m01zw,-m01yw,m01yz));
                adjM0.w=-dot(M[2].yzw,float3(m01zw,-m01yw,m01yz));
                adjM1.x=-dot(M[1].xzw,float3(m23zw,-m23xw,m23xz));
                adjM1.y=+dot(M[0].xzw,float3(m23zw,-m23xw,m23xz));
                adjM1.z=-dot(M[3].xzw,float3(m01zw,-m01xw,m01xz));
                adjM1.w=+dot(M[2].xzw,float3(m01zw,-m01xw,m01xz));
                adjM2.x=+dot(M[1].xyw,float3(m23yw,-m23xw,m23xy));
                adjM2.y=-dot(M[0].xyw,float3(m23yw,-m23xw,m23xy));
                adjM2.z=+dot(M[3].xyw,float3(m01yw,-m01xw,m01xy));
                adjM2.w=-dot(M[2].xyw,float3(m01yw,-m01xw,m01xy));
                adjM3.x=-dot(M[1].xyz,float3(m23yz,-m23xz,m23xy));
                adjM3.y=+dot(M[0].xyz,float3(m23yz,-m23xz,m23xy));
                adjM3.z=-dot(M[3].xyz,float3(m01yz,-m01xz,m01xy));
                adjM3.w=+dot(M[2].xyz,float3(m01yz,-m01xz,m01xy));
                float invDet=rcp(dot(M[0].xyzw,float4(adjM0.x,adjM1.x,adjM2.x,adjM3.x)));
                return transpose(float4x4(adjM0*invDet,adjM1*invDet,adjM2*invDet,adjM3*invDet));
            }

            v2f vert (float4 vertex : POSITION, float2 uv : TEXCOORD0)
            {
                v2f o;
                o.vertex = float4(float2(1,-1)*(uv*2-1),1,1);
                o.clipPos = o.vertex;
                o.inverseVP = inverse(UNITY_MATRIX_VP);
                return o;
            }

            float4 frag (v2f i) : SV_Target
            {
                float4 clipPos = i.clipPos / i.clipPos.w;
                clipPos.z = tex2Dproj(_CameraDepthTexture, ComputeScreenPos(clipPos));
                float4 homWorldPos = mul(i.inverseVP, clipPos);
                float3 wpos = homWorldPos.xyz / homWorldPos.w;
                return float4(wpos, 1.0f);
            }
            ENDCG
        }
    }
}