Unity shaders - specular lighting not reflecting properly

Hi,

I am trying to simulate specular light reflecting from a planet's surface.

The problem I came across is that we can see a glossy spot on the side of the planet that is facing away from the sun.




I tried inverting the lights direction when calculating the dot product, but that causes another problem: it inverts the side of the planets that are lit.






Here is my code. Can you guys help me out?

[ICODE]

[code=CSharp]Shader "Unlit/planetShader"

{

    Properties

    {

        _PlanetColor("Main color",Color) = (1,1,1,1)

        _SpecularGlossStrength("Specular gloss strength",float) = 1

    }

    SubShader

    {

        Tags { "RenderType"="Opaque" }

        LOD 100



        Pass

        {

            CGPROGRAM

            #pragma vertex vert

            #pragma fragment frag





            #include "UnityCG.cginc"



            struct VertexInput

            {

                float4 vertex : POSITION;

                float3 normal : NORMAL;

            };



            struct VertexOutput

            {

                float4 vertex : SV_POSITION;

                float3 normal : TEXCOORD0;

                float3 worldPos : TEXCOORD1;

            };



            // Declare variables here

            float4 _PlanetColor;

            Vector _SunPosition;

            float _SpecularGlossStrength;



            VertexOutput vert (VertexInput input)

            {

               VertexOutput output;

               output.vertex =UnityObjectToClipPos(input.vertex);

               output.worldPos = mul(unity_ObjectToWorld,input.vertex);

               

               //output.uv = TRANSFORM_TEX(vertexInput.uv, _MainTex);



               output.normal = mul(unity_ObjectToWorld, input.normal);







                return output;

            }



            fixed4 frag (VertexOutput output) : SV_Target

            {

        // Diffuse light

        // Based on planet position relative to the sun



        float3 lightDir = normalize(_SunPosition - output.worldPos);



        //float3 lightDir = normalize(float3(1,1,1));



float diffuseLightFallOff = max(.2,dot(lightDir, normalize(output.normal)));



        float3 sunColor = float3(1, 1, 0);



        float3 compositeColor = _PlanetColor + sunColor/2;



        float3 diffuseLight = compositeColor * diffuseLightFallOff;





// Specular light

float3 camToFragDir = normalize(_WorldSpaceCameraPos - output.worldPos);



float3 camToFragDirReflect = reflect(normalize(output.normal), camToFragDir);



    float specularFallOff = max(0,dot(-lightDir, camToFragDirReflect));



    specularFallOff = pow(specularFallOff, _SpecularGlossStrength);





    // Combining lights and colors



    float3 finalColor = (diffuseLight + specularFallOff) * compositeColor;





                return float4(finalColor,1);

            }

            ENDCG

        }

    }

}[/code]

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