shader之——移动端模拟深度水

描述：

在网上看到很多效果很好的水，比如根据水的深度，颜色有深浅变化，能让水变得更真实，但是又会涉及到比较复杂的计算，在移动端上面还是有些吃力的。

最近研究了一下，想在移动端上面模拟这样的效果 ：

1 水的深浅透明度变化

2 水的深浅颜色变化

3 水上的阴影模拟（大面积的水通过烘焙比较浪费烘焙图）

根据上面的3点，可以通过一张黑白图的rg通道来实现深浅以及阴影的模拟 效果如下

如图，浅色的偏绿，深色的偏蓝 ，颜色可以手动调节，左边为阴影位置

代码如下：

Shader "Game_XXX/whater"
{
	Properties 
	{
		_WaterTex ("Normal Map (RGB), Foam (A)", 2D) = "white" {}
		_AlphaTex("AlphaTex", 2D) = "black" {}
		_shadowLight ("shadowLight",range(0,1)) = 0
		_Tiling ("Wave Scale", Range(0.00025, 0.007)) = 0.25
		_WaveSpeed("Wave Speed", Float) = 0.4
		_SpecularRatio ("Specular Ratio", Range(10,500)) = 200
		_outSideColor("outSideColor",Color) = (0,0,0,0)
		_outSideLight("outSideLight",Range(0,10))=1
		_inSideColor("inSideColor",Color) = (0,0,0,0)
		_inSideLight("intSideLight",Range(0,10))=1
		_Alpha("Alpha",Range(0,1)) = 1
		//模拟灯光颜色
		_LightColorSelf ("LightColorSelf",Color) = (1,1,1,1)
		//模拟灯光方向
		_LightDir ("LightDir",vector) = (0,1,0,0)
		//高光强度
		_specularLight("specularLight",range(0.1,2)) =1	
	}
	
	SubShader {  
		Tags {
			"Queue"="Transparent-200"
			"RenderType"="Transparent" 
			"IgnoreProjector" = "True"
			"LightMode" = "ForwardBase"
		}
		LOD 250
		Pass
		{

			 ZWrite Off
			 Blend SrcAlpha OneMinusSrcAlpha
			 CGPROGRAM

			 #pragma vertex Vert
			 #pragma fragment Frag
			 #include "UnityCG.cginc"
			
			 float _Tiling;
			 float _WaveSpeed;
			 float _SpecularRatio;
			 sampler2D _WaterTex;
			 sampler2D _AlphaTex;
			 float4 _LightColorSelf;
			 float4 _LightDir;
			 float4 _outSideColor;
			 float _outSideLight;
			 float4 _inSideColor;
			 float _inSideLight;
			 float _shadowLight;
			 float _specularLight;
			 float _Alpha;

			struct v2f
			{
			 float4 position  : POSITION;
			 float3 worldView  : TEXCOORD0;
			 float3 tilingAndOffset:TEXCOORD2;
			 float3x3 tangentTransform:TEXCOORD4;  
			 float2 alphaUV :TEXCOORD7;

			};

			

			v2f Vert(appdata_full v)
			{
			 v2f o;
			 float4 worldPos = mul(unity_ObjectToWorld, v.vertex);
			 //视向量（世界空间）
			 o.worldView = -normalize(worldPos - _WorldSpaceCameraPos);
			 o.position = UnityObjectToClipPos(v.vertex);
			 //uv动画
			 o.tilingAndOffset.z =frac( _Time.x * _WaveSpeed);//frac :返回标量或矢量的小数
			 o.tilingAndOffset.xy = worldPos.xz*_Tiling;
			 o.alphaUV = v.texcoord;
			 //求世界法线三件套  
			 float3 normal =normalize( UnityObjectToWorldNormal(v.normal));  
             float3 tangentDir = normalize( mul( unity_ObjectToWorld, float4( v.tangent.xyz, 0.0 ) ).xyz );//切线空间转化为世界空间  
             float3 bitangentDir = normalize(cross(normal, tangentDir) * v.tangent.w);//切线 法线 计算副切线  

			 o.tangentTransform = float3x3( tangentDir, bitangentDir, normal);  
			 return o;
			}

			float4 Frag(v2f i):COLOR
			{

			  

			  //法线采样
			  fixed3 BumpMap01 = UnpackNormal(tex2D(_WaterTex,i.tilingAndOffset.xy + i.tilingAndOffset.z ));
			  fixed3 BumpMap02 = UnpackNormal(tex2D(_WaterTex,i.tilingAndOffset.xy*1.1 - i.tilingAndOffset.z));
			  //两张法线相混合
			  //fixed3 N1 =saturate( normalize(mul( BumpMap01.rgb, i.tangentTransform )));
			  //fixed3 N2 =saturate( normalize(mul( BumpMap02.rgb, i.tangentTransform )));
			  //fixed3 worldNormal  =  N1 - float3(N2.x,0,N2.z);

			  fixed3 N1 = normalize(mul( BumpMap01.rgb, i.tangentTransform ));
			  fixed3 N2 = normalize(mul( BumpMap02.rgb, i.tangentTransform ));
			  fixed3 worldNormal = N1*0.5 +N2*0.5;




			  float LdotN = dot(worldNormal, _LightDir.xyz); //_LightDir为模拟灯光
			 

			  //高光 
			  float dotSpecular = dot(worldNormal,  normalize( i.worldView+_LightDir.xyz));
			  fixed3 specularReflection = pow(saturate(dotSpecular), _SpecularRatio)*_specularLight;


			  //通道贴图采样
			  fixed4 alphaTex = tex2D (_AlphaTex,i.alphaUV);
			  //模拟灯光的颜色 * 漫反射系数= 基础水的颜色
			  fixed4 col =_LightColorSelf*2 * saturate (LdotN) ;
			  //用alpha贴图的r通道来模拟水的深浅的颜色，白色为深色，黑色为浅色 ，同时乘以想要的颜色
			  col.rgb = col.rgb * alphaTex.r *_inSideColor * _inSideLight  +  col.rgb * (1-alphaTex.r) * _outSideColor *_outSideLight + specularReflection;

			  //控制透明度，根据alpha的r通道 来控制深浅的透明度，深色的透明度小 浅色的透明度大
			  col.a = _Alpha * alphaTex.r;

			  //手动绘制阴影 用alpha贴图的g通道 跟col相乘 来模拟阴影 
			  alphaTex.g = saturate(alphaTex.g + _shadowLight);
			  col.rgb *= alphaTex.g;
			  return col;
			}
		      ENDCG	
	    }  
	}

	FallBack "Diffuse"
}