Simulate fog with gradient shader

Unity Engine
1

Hello Everyone!

I am having a little problem with making fog effect in my Unity game. Have a look at the picture:

The effect is achieved by having a shader that applies color gradients to the towers. All looks good, but when I add lights to the scene, it changes to this:

Oops. The fog effect disappeared. I am happy with the shading effect on the upper parts of the towers, but the lower part should still get solid blue. My shader looks like this:

Shader "Custom/ColorGradient" {
    Properties {
        _ColorA ("ColorA", Color) = (1,1,1,1)
        _ColorB ("ColorB", Color) = (1,1,1,1)
        _Start ("Start", Float) = 2.0
        _End ("End", Float) = 1.0
    }
    SubShader {
        Tags { "RenderType"="Opaque" }
        LOD 200
       
        CGPROGRAM
        #pragma surface surf Lambert

        float4 _ColorA;
        float4 _ColorB;
        float _Start;
        float _End;

        struct Input {
            float2 uv_MainTex;
            float3 worldPos;
        };

        void surf (Input IN, inout SurfaceOutput o) {
            if(IN.worldPos.y>_Start){
                o.Albedo = _ColorA.rgb;
                o.Emission = 0;
            }
            if(IN.worldPos.y<=_Start && _End<=IN.worldPos.y) {
                float d = (IN.worldPos.y-_End)/(_Start-_End);
                o.Albedo = lerp(_ColorA, _ColorB, 1.0-d).rgb;
                o.Emission =  (1.0-d) * lerp(_ColorA, _ColorB, 1.0-d).rgb;
            }
            if(IN.worldPos.y<_End) {
                o.Albedo = _ColorB.rgb;
                o.Emission = _ColorB.rgb;
            }
        }
        ENDCG
    }
    FallBack "Diffuse"
}

Does anyone know how to fix this? Thanks a lot in advance for any suggestions.

2

You should not use emission, implement your own lighting function, pass fog color in it and add to final color with lerp function.