Change generated mesh texture based on dot product

I am generating a hexagon map and want to change the normal maps depending on the elevation rising. I initially thought i can base it on a dot product but i keep getting the wrong results out of it.

This is what i get

This is the area i wanted to be affected by the red part. It's the elevation to a higher level hexagon.

This is the code, it currently passes onto the albedo instead of o.Normal to visualize it better. The code is based on catlikecoding.

         //frag
         void surf (Input IN, inout SurfaceOutputStandardSpecular o) {
             //pass normal in again to counteract bug
             IN.worldNormal = WorldNormalVector(IN, float3(0,0,1));
 
             fixed4 c = 
             //last coordinate is texarray index
                 GetTerrainColor(IN, 0) +
                 GetTerrainColor(IN, 1) +
                 GetTerrainColor(IN, 2);
 
             //DP for normalmap
             float3 dir = _HexCellData_TexelSize - IN.worldPos;
             float t = 0.5 + sign(dot(dir, o.Normal)) * 0.5;
             o.Albedo = c.rgb * lerp(_Color2.rgb, _Color.rgb, t);

The _HexCellData_TexelSize is from a separate C# script on the object and passes the following onto a cginc file that's included.

 Shader.SetGlobalVector("_HexCellData_TexelSize", new Vector4(1f / x, 1f / z, x, z));

Maybe i pass the wrong Vector? I still dont fully understand the whole syntax around dot products. Any help appreciated thank you.