Unity 地形shader atlas纹理接缝问题

头上长西瓜 2017-12-26 10:47:48

这是魔兽争霸用的地形纹理图集
http://www.cnblogs.com/sifenkesi/archive/2011/03/03/1970051.html
这个帖子介绍了纹理的拼接方式
最近想用unity仿照着写一个shader,大体基本实现了,但是在子纹理的连接处出现了接缝的问题,如下图

附上shader,请大侠们帮忙分析一下原因

// Unity built-in shader source. Copyright (c) 2016 Unity Technologies. MIT license (see license.txt)



Shader "Nature/Terrain/Standard" {

	Properties {

		// set by terrain engine

		[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" {}

		[HideInInspector] _Normal3 ("Normal 3 (A)", 2D) = "bump" {}

		[HideInInspector] _Normal2 ("Normal 2 (B)", 2D) = "bump" {}

		[HideInInspector] _Normal1 ("Normal 1 (G)", 2D) = "bump" {}

		[HideInInspector] _Normal0 ("Normal 0 (R)", 2D) = "bump" {}

		[HideInInspector] [Gamma] _Metallic0 ("Metallic 0", Range(0.0, 1.0)) = 0.0	

		[HideInInspector] [Gamma] _Metallic1 ("Metallic 1", Range(0.0, 1.0)) = 0.0	

		[HideInInspector] [Gamma] _Metallic2 ("Metallic 2", Range(0.0, 1.0)) = 0.0	

		[HideInInspector] [Gamma] _Metallic3 ("Metallic 3", Range(0.0, 1.0)) = 0.0

		[HideInInspector] _Smoothness0 ("Smoothness 0", Range(0.0, 1.0)) = 1.0	

		[HideInInspector] _Smoothness1 ("Smoothness 1", Range(0.0, 1.0)) = 1.0	

		[HideInInspector] _Smoothness2 ("Smoothness 2", Range(0.0, 1.0)) = 1.0	

		[HideInInspector] _Smoothness3 ("Smoothness 3", Range(0.0, 1.0)) = 1.0



		// 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 {

			"Queue" = "Geometry-100"

			"RenderType" = "Opaque"

		}



		CGPROGRAM

		#pragma surface surf Lambert

		#pragma target 3.0



		struct Input

		{

		    float2 uv_Splat0 : TEXCOORD0;

		    float2 uv_Control : TEXCOORD4;

		};

		sampler2D _Control,_Splat0,_Splat1,_Splat2,_Splat3;

		half _Metallic0;

		half _Metallic1;

		half _Metallic2;

		half _Metallic3;



		void surf (Input IN, inout SurfaceOutput o) {

			half4 BlendTex = tex2D(_Control, IN.uv_Control);

			half4 lay0={0.0,0.0,0.0,0.0},lay1={0.0,0.0,0.0,0.0},lay2={0.0,0.0,0.0,0.0},lay3={0.0,0.0,0.0,0.0};

			float2 xy;half k;



			k = round(BlendTex.r * 256.0);

			if(k>0&&k<33){

				xy.x = floor(k / 4)/8;

				xy.y = (3-fmod(k, 4))/4;

				lay0 = tex2D(_Splat0,frac(IN.uv_Splat0)/float2(8,4)+xy,ddx(IN.uv_Splat0/float2(8,4)),ddy(IN.uv_Splat0/float2(8,4)));

			}

			k = round(BlendTex.g * 256.0);

			if(k>0&&k<33){

				xy.x = floor(k / 4)/8;

				xy.y = (3-fmod(k, 4))/4;

				lay1 = tex2D(_Splat1,frac(IN.uv_Splat0)/float2(8,4)+xy,ddx(IN.uv_Splat0/float2(8,4)),ddy(IN.uv_Splat0/float2(8,4)));

			}

			k = round(BlendTex.b * 256.0);

			if(k>0&&k<33){

				xy.x = floor(k / 4)/8;

				xy.y = (3-fmod(k, 4))/4;

				lay2 = tex2D(_Splat2,frac(IN.uv_Splat0)/float2(8,4)+xy,ddx(IN.uv_Splat0/float2(8,4)),ddy(IN.uv_Splat0/float2(8,4)));

			}

			k = round(BlendTex.a * 256.0);

			if(k>0&&k<33){

				xy.x = floor(k / 4)/8;

				xy.y = (3-fmod(k, 4))/4;

				lay3 = tex2D(_Splat3,frac(IN.uv_Splat0)/float2(8,4)+xy,ddx(IN.uv_Splat0/float2(8,4)),ddy(IN.uv_Splat0/float2(8,4)));

			}

			float4 finalColor;

			finalColor=lerp(lay0,lay1,lay1.a);

			finalColor=lerp(finalColor,lay2,lay2.a);

			finalColor=lerp(finalColor,lay3,lay3.a);

			o.Albedo.rgb=finalColor;

		}

		ENDCG

	}



	Dependency "AddPassShader" = "Hidden/TerrainEngine/Splatmap/Standard-AddPass"

	Dependency "BaseMapShader" = "Hidden/TerrainEngine/Splatmap/Standard-Base"



	Fallback "Nature/Terrain/Diffuse"

}