A masked-blend terrain shader hack for Unity.

Terrain_FirstPass.shader

Shader "Nature/Terrain/Diffuse" {
Properties {
  [HideInInspector] _Control ("Control (RGBA)", 2D) = "red" {}
	[HideInInspector] _Splat3 ("Layer 3 (A)", 2D) = "white" {}
	[HideInInspector] _Splat2 ("Layer 2 (B)", 2D) = "white" {}
	[HideInInspector] _Splat1 ("Layer 1 (G)", 2D) = "white" {}
	[HideInInspector] _Splat0 ("Layer 0 (R)", 2D) = "white" {}
	// used in fallback on old cards & base map
	[HideInInspector] _MainTex ("BaseMap (RGB)", 2D) = "white" {}
	[HideInInspector] _Color ("Main Color", Color) = (1,1,1,1)
}
	
SubShader {
	Tags {
		"SplatCount" = "4"
		"Queue" = "Geometry-100"
		"RenderType" = "Opaque"
	}
CGPROGRAM
#pragma surface surf Lambert
struct Input {
	float2 uv_Control : TEXCOORD0;
	float2 uv_Splat0 : TEXCOORD1;
	float2 uv_Splat1 : TEXCOORD2;
	float2 uv_Splat2 : TEXCOORD3;
	float2 uv_Splat3 : TEXCOORD4;
};

sampler2D _Control;
sampler2D _Splat0,_Splat1,_Splat2,_Splat3;

void surf (Input IN, inout SurfaceOutput o) {
	fixed4 splat_control = tex2D (_Control, IN.uv_Control);
	fixed3 col;
	col  = splat_control.r * tex2D (_Splat0, IN.uv_Splat0).rgb;
	col += splat_control.g * tex2D (_Splat1, IN.uv_Splat1).rgb;
	col += splat_control.b * tex2D (_Splat2, IN.uv_Splat2).rgb;
	col = col * clamp(pow(1 - splat_control.a * 1.1 - splat_control.a * tex2D (_Splat3, IN.uv_Splat3).a, 3.4), 0, 1) + tex2D (_Splat3, IN.uv_Splat3).rgb * clamp(splat_control.a * 3.0 + splat_control.a * tex2D (_Splat3, IN.uv_Splat3).a * 4, 0.0, 1.0);
	o.Albedo = col;
	o.Alpha = 0.0;
}
ENDCG  
}

Dependency "AddPassShader" = "Hidden/TerrainEngine/Splatmap/Lightmap-AddPass"
Dependency "BaseMapShader" = "Diffuse"
Dependency "Details0"      = "Hidden/TerrainEngine/Details/Vertexlit"
Dependency "Details1"      = "Hidden/TerrainEngine/Details/WavingDoublePass"
Dependency "Details2"      = "Hidden/TerrainEngine/Details/BillboardWavingDoublePass"
Dependency "Tree0"         = "Hidden/TerrainEngine/BillboardTree"

// Fallback to Diffuse
Fallback "Diffuse"
}