Alpha Map Shader

Shader "Custom/AlphaMapShader"
{
    Properties
    {
        // Main Texture
        _MainTex ("Main Texture", 2D) = "white" {}
        // Alpha Map Texture
        _AlphaMapTex ("Alpha Texture", 2D) = "white" {}
        // Color to key out
        _KeyOutColor ("Key Out Color (BG Color)", Color) = (0,0,0,1)
    }
    SubShader
    {
        Tags
        {
            "Queue"="Transparent"
            "RenderType"="Transparent"
        }

        // These four lines below fixed my issue with different shaders behaving weird when on top of each other!
        LOD 100
        ZWrite Off
        ZTest Off
        Blend SrcAlpha OneMinusSrcAlpha

        CGPROGRAM
        #pragma surface surf Lambert alpha
        #pragma target 3.0
        #include "UnitySprites.cginc"

        struct Input
        {
            // The position of the vertex after being transformed into projection space: http://wiki.unity3d.com/index.php?title=Shader_Code
            float4 position  : SV_POSITION;
            // The uv of the main texture (UV Coordinates, is xy values of texture between 0 and 1): http://wiki.winamp.com/wiki/Pixel_Shader_Basics
            // aka First texture coordinate, or UV: http://wiki.unity3d.com/index.php?title=Shader_Code
            float2 uv_MainTex : TEXCOORD0;
            // The uv of the alpha map texture (UV Coordinates, is xy values of texture between 0 and 1): http://wiki.winamp.com/wiki/Pixel_Shader_Basics
            // aka Second texture coordinate, or UV (only 2 UV coords currently supported, but there are ways to bypass): http://wiki.unity3d.com/index.php?title=Shader_Code
            float2 uv_AlphaMapTex : TEXCOORD1;
        };

        // sampler2D _MainTex;

        // I think this samples from the Alpha Map Texture but not 100% sure, check these sources to find out: https://www.khronos.org/opengl/wiki/Sampler_(GLSL) and https://stackoverflow.com/questions/10868958/what-does-sampler2d-store
        sampler2D _AlphaMapTex;
        // uses the Key Out Color definied above (in properties)
        float4 _KeyOutColor;

        // IN is the input (struct of Input is defined above), and o is the output
        void surf (Input IN, inout SurfaceOutput o)
        {
            // sets the color of the output texture (Albedo) to the rgb value of the main texture at the current uv point: https://forum.unity.com/threads/what-is-albedo-and-what-does-it-do.246182/ and https://developer.download.nvidia.com/cg/tex2D.html
            o.Albedo = tex2D (_MainTex, IN.uv_MainTex).rgb;
            // creates a variable that equals the color of the key out color subtracted from the color of the output
            float3 diff = o.Albedo.rgb - _KeyOutColor.rgb;

            /*
            if (diff.r < 0f)
                diff.r *= -1f;
            if (diff.g < 0f)
                diff.g *= -1f;
            if (diff.b < 0f)
                diff.b *= -1f;

            // if (all(o.Albedo.rgb == _KeyOutColor.rgb))
            //     o.Alpha = 0;
            if (all(diff < 0.1f)
                o.Alpha = 0f;
            */

            // if(!any(diff > 0.1 || diff < -0.1))

            // if the difference of all the values for this uv point is less than 0.1 from the key out color, then we set the alpha of
            // the output to 0, otherwise the alpha is set to the "alpha" of the alpha map texture at the current uv point of the alpha
            // map texture (I used the red channel instead of the alpha channel so that the alpha map texture could be from black to white
            // instead of from 100% opacity to 0% opacity, since this is how most alpha maps are done that I have seen AND it is far easier
            // to work with when making the actual alpha map textures, so basically white is full opacity and black is no opacity in the
            // alpha map texture)
            if (all(diff < 0.1) && all(diff > -0.1))
                o.Alpha = 0;
            else
                o.Alpha = tex2D (_AlphaMapTex, IN.uv_AlphaMapTex).r; // Could use .a, but this way we can use black to white for alpha
        }

        ENDCG
    }
    Fallback "Diffuse"
 }