Problem with Light direction shader

Hi, I need some help with a light direction shader. I'm trying to do this in the picture.

As you can see by using the light and adding a custom gradient based on the light direction. Now I can do this with a colorRamp, but I would like to know how to do it with colors instead of a texture then creating my own gradient with that.

I have been trying to achieve whats in the picture above, but its not getting the light direction for some reason, but it is doing the gradient. I don't know how to fix this.
I will have the code and shader setting configuration below.


*Shader Configuration*

*Here is the code*

Shader "LightDirGradient" {

 Properties {

    _MainTex ("Base (RGB)", 2D) = "white" {}

    _Color1 ("Bottom Color", Color) = (0,0,1,1)

    _Color2 ("Top Color", Color) = (1,0,0,1)

    _Scale ("Scale", Float) = 1

    _Offset ("Offset", Float) = 0

    _Glossiness ("Smoothness", Range(0,1)) = 0.5

    _Metallic ("Metallic", Range(0,1)) = 0.0

   //_LightDir ("LightDir", Vector) = (0, 0, 0, 0)    

 }

 SubShader {

    Tags { "RenderType"="Opaque" }

    LOD 200

    CGPROGRAM

    #pragma surface surf Standard fullforwardshadows vertex:vert

    #pragma target 3.0

    sampler2D _MainTex;

    half _Glossiness;

    half _Metallic;

    fixed4 _Color1;

    fixed4 _Color2;

   float4 _LightDir;

    fixed  _Scale;

    fixed  _Offset;

    struct Input {

        float2 uv_MainTex;

        float3 lightDir;

    };

    void vert (inout appdata_full v, out Input o){

        UNITY_INITIALIZE_OUTPUT(Input,o);

       float4 vertWorldPos = mul(_Object2World, v.vertex);

        half dotP = (dot(normalize(v.vertex.xyz - vertWorldPos), _WorldSpaceLightPos0.xyz));

        o.lightDir = _LightColor0.rgb * dotP;

    }

    void surf (Input IN, inout SurfaceOutputStandard o) {

        half4 c = tex2D(_MainTex, IN.uv_MainTex);

        c.rgb *= lerp(_Color1,_Color2, (IN.lightDir.xyz * _Scale) +_Offset );

        o.Albedo = c.rgb;

        o.Alpha = c.a;

        o.Metallic = _Metallic;

        o.Smoothness = _Glossiness;

    }

    ENDCG

 }

 Fallback "Diffuse"

 }

 

You are not specifying the render pass in which this shader would be called. If you're using Forward rendering, you have to set a pass with a LightMode = "ForwardBase" or Unity won't supply any of the _WorldSpaceLightPos0 uniforms for you