Texture Splatting.shader

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Custom/Texture Splatting" {

	Properties {
		_MainTex ("Splat Map", 2D) = "white" {}
		[NoScaleOffset] _Texture1 ("Texture 1", 2D) = "white" {}
		[NoScaleOffset] _Texture2 ("Texture 2", 2D) = "white" {}
		[NoScaleOffset] _Texture3 ("Texture 3", 2D) = "white" {}
		[NoScaleOffset] _Texture4 ("Texture 4", 2D) = "white" {}
	}

	SubShader {

		Pass {
			CGPROGRAM

			#pragma vertex MyVertexProgram
			#pragma fragment MyFragmentProgram

			#include "UnityCG.cginc"

			sampler2D _MainTex;
			float4 _MainTex_ST;

			sampler2D _Texture1, _Texture2, _Texture3, _Texture4;

			struct VertexData {
				float4 position : POSITION;
				float2 uv : TEXCOORD0;
			};

			struct Interpolators {
				float4 position : SV_POSITION;
				float2 uv : TEXCOORD0;
				float2 uvSplat : TEXCOORD1;
			};

			Interpolators MyVertexProgram (VertexData v) {
				Interpolators i;
				i.position = UnityObjectToClipPos(v.position);
				i.uv = TRANSFORM_TEX(v.uv, _MainTex);
				i.uvSplat = v.uv;
				return i;
			}

			float4 MyFragmentProgram (Interpolators i) : SV_TARGET {
				float4 splat = tex2D(_MainTex, i.uvSplat);
				return
					tex2D(_Texture1, i.uv) * splat.r +
					tex2D(_Texture2, i.uv) * splat.g +
					tex2D(_Texture3, i.uv) * splat.b +
					tex2D(_Texture4, i.uv) * (1 - splat.r - splat.g - splat.b);
			}

			ENDCG
		}
	}
}