Lightprobe Alpha Diffuse Matcap Shader

Shader "FX/MatcapDiffuse_Alpha"
{
    Properties
    {
        _MainTex ("Base (RGB)", 2D) = "white" {}
        _MatCap ("MatCap (RGB)", 2D) = "white" {}
        _Alpha ("Alpha", float) = 0.5
    }

    Subshader
    {
        Blend SrcAlpha OneMinusSrcAlpha
        Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
        Cull Back
        Fog { Mode Off }


        Pass
        {
            Name "BASE"
            Tags { "LightMode" = "ForwardBase" }

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma fragmentoption ARB_precision_hint_fastest
            #pragma multi_compile LIGHTMAP_ON LIGHTMAP_OFF
            #include "UnityCG.cginc"

            uniform sampler2D _MatCap;

            uniform sampler2D _MainTex;
            uniform fixed4 _MainTex_ST;

            uniform fixed _Alpha;

                struct v2f
                {
                    fixed4 pos : SV_POSITION;
                    fixed2  uv : TEXCOORD0;

                    fixed2 cap : TEXCOORD3;
                };

                v2f vert (appdata_full v)
                {
                    v2f o;

                    o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                    o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);

                    fixed2 capCoord;
                    capCoord.x = dot(UNITY_MATRIX_IT_MV[0].xyz, v.normal);
                    capCoord.y = dot(UNITY_MATRIX_IT_MV[1].xyz, v.normal);

                    o.cap = capCoord * 0.5 + 0.5;

                    return o;
                }

                float4 frag (v2f i) : COLOR
                {
                    fixed4 tex = tex2D(_MainTex, i.uv.xy);

                    fixed4 matcapLookup = tex2D(_MatCap, i.cap);

                    // matcapLookup.a = tex.a;

                    tex *= matcapLookup * 2.0;

                    tex.a = _Alpha;

                    return tex;
                }

            ENDCG

        }

    }
}