Shader "HeightTest"
{
    Properties
	{
        _MainTex ("Base (RGB) Trans (A)", 2D) = "white" { }
		_Cutoff ("Alpha Cutoff", Range(0,1)) = 0.5
    }

    SubShader
	{
		Tags { "QUEUE"="Transparent" "IGNOREPROJECTOR"="true" "RenderType"="Transparent" }
		LOD 200
		ZWrite On

        // Set up alpha blending
        Blend SrcAlpha OneMinusSrcAlpha
		
		Pass 
		{ 
			Cull Back
			Lighting Off 
			Alphatest Equal [_Cutoff] 
			SetTexture [_MainTex] 
			{ 
				combine texture
			} 
		}
		CGPROGRAM
		#pragma surface surf NoLighting
	
		fixed4 LightingNoLighting(SurfaceOutput s, fixed3 lightDir, fixed atten)
		{
			fixed4 c;
			c.rgb = s.Albedo;
			c.a = s.Alpha;
			return c;
		}
		
		
		sampler2D _MainTex;
		uniform float _PlayerY = 0;
		
		struct Input {
			float2 uv_MainTex;
			float3 worldPos;
		};
		
		void surf (Input IN, inout SurfaceOutput o)
		{
			half4 c = tex2D (_MainTex, IN.uv_MainTex);
			half junk;
			
			half darkMult = IN.worldPos.y - (_PlayerY-1);
			half darkSmooth = modf(darkMult, junk)*8; //The multiplier here determines the smoothing between layers
			darkMult = (ceil(darkMult+2)/12)+.67; //Base the layer darkness off the player position and a scalar
			if(ceil(darkSmooth) == 0) //If near edge of current shading stage
				darkMult += 0.09 + modf(darkSmooth, junk)/12; //Use the second decimal place as a smoothing value between stages
				
			half alpha = (IN.worldPos.y - _PlayerY - 1.5)/3;
			
			if(darkMult > 1) darkMult = 1;
			if(darkMult < 0.15) darkMult = 0.15;
			if(alpha > 1) alpha = 1;
			if(alpha < 0) alpha = 0;
			
			if (IN.worldPos.y < _PlayerY-1) {
				o.Albedo = c.rgb * darkMult;
			}
			else {
				o.Albedo = c.rgb * .92;
			}
			if (IN.worldPos.y > _PlayerY + 1.5) {
				o.Alpha = c.a * (1-alpha);
			}
			else {
				o.Alpha = c.a;
			}
		}
		ENDCG
    }
}