Shader "Custom/Terrain"
{
    Properties {
        _Color ("Color", Color) = (1,1,1,1)
        _BlendMin("BlendMin", Range(0,1)) = 0.5
        _BlendMax("BlendMax", Range(0,1)) = 0.6
        
        _MainTex ("MainTexture", 2D) = "white" {}
        _MudTex ("Mud", 2D) = "white" {}
        _GrassTex ("Grass", 2D) = "white" {}
        _NoiseTex  ("Noise", 2D) = "white" {}
    }
    SubShader {
        Tags { "RenderType" = "Opaque" }
        CGPROGRAM
        #pragma surface surf Lambert
        #pragma target 3.0

        sampler2D _MainTex;
        fixed4 _Color;
        fixed _BlendMin;
        fixed _BlendMax;
        sampler2D _MudTex;
        sampler2D _GrassTex;
        sampler2D _NoiseTex;

        struct Input
        {
            float2 uv_MainTex;
            float2 uv_MudTex;
            float2 uv_GrassTex;
            float2 uv_NoiseTex;
        };

        void surf (Input IN, inout SurfaceOutput o) {
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
            fixed4 mud = tex2D(_MudTex, IN.uv_MudTex);
            fixed4 grass = tex2D(_GrassTex, IN.uv_GrassTex);

            fixed2 uvNoise = IN.uv_NoiseTex;
            uvNoise.x += 0.01*_Time.y;
            fixed4 noise = tex2D(_NoiseTex, uvNoise);
            fixed3 col =float3(1,1,1);
            if(c.r<_BlendMin){
                col=grass.rgb;
            }
            else if(c.r>_BlendMax){
                col=mud.rgb;
            }
            else{
                col = lerp(grass.rgb, mud.rgb,(c.r-_BlendMin)/(_BlendMax-_BlendMin));
            }
            if(noise.r<0.5){
                col *=noise*2;
            }
            o.Albedo = col;
            o.Alpha = c.a;
        }
        ENDCG
    }
    FallBack "Diffuse"
}