Shader "Custom/TerrainMapper" {
    Properties {
        _LowlandTex ("Grass", 2D)     = "white" {}
      _HighlandTex("HighGrass", 2D) = "white" {}
      _LowwallTex ("Stone", 2D)     = "white" {}
      _HighwallTex("HighStone", 2D) = "white" {}

      _LowlandNorm ("GrassBump", 2D)     = "bump" {}
      _HighlandNorm("HighGrassBump", 2D) = "bump" {}
      _LowwallNorm ("StoneBump", 2D)     = "bump" {}
      _HighwallNorm("HighStoneBump", 2D) = "bump" {}

      _HeightDiff("Height", Float)       = 100
      _HeightMix ("MixingOffset", Float) = 3
    }
    SubShader {
        Tags { "RenderType"="Opaque" }
        LOD 200

        CGPROGRAM
        #pragma surface surf Lambert
      #pragma target 3.0

      #define PI 22/7

        sampler2D _LowlandTex, _HighlandTex, _LowwallTex, _HighwallTex, _LowlandNorm, _HighlandNorm, _LowwallNorm, _HighwallNorm;

      float _HeightDiff, _HeightMix;

        struct Input {
            float2 uv_LowlandTex;
         float3 worldPos;
         float3 worldNormal;
        };

        void surf (Input IN, inout SurfaceOutput o) {;

         float deg = (1 - IN.worldNormal.y);
         deg = (deg * 1.5);
         if (deg > 1) deg = 1;
         deg = (sin(deg * PI - PI * 0.5) + 1) * 0.5;

         float height = IN.worldPos.y;
         half4 c;
         half4 b;
         if (height > _HeightDiff + _HeightMix) {
            c =  tex2D (_HighwallTex, IN.uv_LowlandTex) * deg;
            c += tex2D (_HighlandTex, IN.uv_LowlandTex) * (1 - deg);

            b =  tex2D (_HighwallNorm, IN.uv_LowlandTex) * deg;
            b += tex2D (_HighlandNorm, IN.uv_LowlandTex) * (1 - deg);

         } else if (height > _HeightDiff - _HeightMix){
            float k = (_HeightDiff + _HeightMix - height) / (_HeightMix * 2.0);
            half4 c1, b1;

            c =  tex2D (_HighwallTex, IN.uv_LowlandTex) * deg;
            c += tex2D (_HighlandTex, IN.uv_LowlandTex) * (1 - deg);

            b =  tex2D (_HighwallNorm, IN.uv_LowlandTex) * deg;
            b += tex2D (_HighlandNorm, IN.uv_LowlandTex) * (1 - deg);

            c *= (1 - k);
            b *= (1 - k);

            c1 =  tex2D (_LowwallTex, IN.uv_LowlandTex) * deg;
            c1 += tex2D (_LowlandTex, IN.uv_LowlandTex) * (1 - deg);

            b1 =  tex2D (_LowwallNorm, IN.uv_LowlandTex) * deg;
            b1 += tex2D (_LowlandNorm, IN.uv_LowlandTex) * (1 - deg);

            c += c1 * k;
            b += c1 * k;
         } else {
            c =  tex2D (_LowwallTex, IN.uv_LowlandTex) * deg;
            c += tex2D (_LowlandTex, IN.uv_LowlandTex) * (1 - deg);

            b =  tex2D (_LowwallNorm, IN.uv_LowlandTex) * deg;
            b += tex2D (_LowlandNorm, IN.uv_LowlandTex) * (1 - deg);
         }
            o.Albedo = c.rgb;
            o.Alpha = c.a;

         //o.Normal = UnpackNormal(tex2D (_LowlandNorm, IN.uv_LowlandTex));
         o.Normal = half3(0, 0, 0);//tex2D(_LowlandNorm, IN.uv_LowlandTex).xyz * 2 - 1;

        }
        ENDCG
    }
    FallBack "Diffuse"
}