三、效果实现：8、水（2）透明效果

通常情况下，水都是透明的，在上次基础上加上透明效果。
核心原理是对对背景采样。

Shader "Customer/Water01"
{
    Properties
    {
        _Color("Color水颜色", color) = (0,0,0.8,0.5)
        _WaveNormalMap("Wave Normal Map", 2D) = "bump"{}
        _WaveHeight("Wave Height",Range(0,1)) = 0.1
        _WaveNormalScale("Wave Scale", float) = 10.0
        _WaveNormalSpeed("Wave Speed", float) = 1.0
        _waveNumber("Wave Number",float) = 4
        _BigWaveSpeed("Big Wave Speed",float) = 10
        _BigWaveHeight("Big Wave Height",float) = 0.5
        _BigWaveNumber("Big Wave Number",float) = 10
        _Opacity("不透明度", range(0, 1)) = 0.5
    }
    SubShader
    {
        Tags
        {
            "Queue" = "Transparent"
            "RenderType" = "Transparent"
        }
        GrabPass{
            "_GrabPassTex"
        }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"
            #include "Lighting.cginc" 
            #pragma multi_compile_fog

            float4 _Color;
            sampler2D _WaveNormalMap;
            fixed _WaveHeight;
            float _WaveNormalScale;
            fixed _WaveNormalSpeed;
            fixed _waveNumber;

            fixed _dividHeight;
            fixed _BigWaveSpeed;
            fixed _BigWaveHeight;
            fixed _BigWaveNumber;

            // 输入参数
            float4 _MainTex_ST;
            uniform half _Opacity;

            sampler2D _GrabPassTex;//用于渲染透明物体
            uniform sampler2D_float _CameraDepthTexture;

            // 输入结构
            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
                float3 normal:NORMAL;//法线通常都是必须的
                float4 tangent : TANGENT;
                float3 color:COLOR0;
            };
            // 输出结构
            struct v2f
            {
                float4 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;   // 由模型顶点信息换算而来的顶点屏幕位置
                float depth : TEXCOORD2;
                float3 normal:NORMAL;//法线通常都是必须的
                float4 lightDir_Tangent:TEXCOORD5;
                float4 screenuv:TEXCOORD1;
                float3 viewDir:TEXCOORD3;
                float4 vertex_Local : TEXCOORD4;
                float3 color:COLOR0;
            };
            
            // 输入结构>>>顶点Shader>>>输出结构
            v2f vert (appdata v)
            {
                v2f o;
                UNITY_INITIALIZE_OUTPUT(v2f, o);
                //获取自身深度值
                COMPUTE_EYEDEPTH(o.depth);

                float2 flow = float2(_Time.x*_WaveNormalSpeed, _Time.z*1.215*_WaveNormalSpeed);

                fixed3 n = UnpackNormal(tex2Dlod(_WaveNormalMap, float4(v.uv.xy*_WaveNormalScale + flow, 0, 0))).xyz;
                //float tempN = tex2Dlod(_WaveNormalMap, float4(v.uv.xy*_WaveNormalScale + flow, 0, 0)).g;这种写法也可以，当然下面的高度也要用下面这句
                //v.vertex.y = v.vertex.y + tempN * _WaveHeight + height;

                float height = 0;

                fixed wavebevel = 5;

                fixed attenuation = (1.0 - v.uv.y);

                fixed b = 0.8;
                fixed x = v.uv.y + b * sin(v.uv.y);
                if (v.vertex.y > _dividHeight)
                {
                    height = (cos(x*_BigWaveNumber - _Time.z*_BigWaveSpeed + v.uv.x*wavebevel) + 1)*0.5*_BigWaveHeight*attenuation;
                    height += (cos(x*_BigWaveNumber - _Time.z*_BigWaveSpeed + (1.0 - v.uv.x)*wavebevel) + 1)*0.5*_BigWaveHeight*attenuation;
                }
                v.vertex.y = v.vertex.y + n * _WaveHeight + height;
                

                if (v.vertex.y > _dividHeight)
                    v.vertex.z -= height * 0.1;

                o.vertex = UnityObjectToClipPos(v.vertex);

                //屏幕UV
                o.screenuv = ComputeScreenPos(o.vertex);// 背景纹理采样坐标
                UNITY_TRANSFER_FOG(o, o.vertex);
                return o;
            }

            fixed4 texCross(sampler2D tex, float2 uv, float speed)
            {
                float4 col1 = tex2D(tex, uv + float2(-_Time.x * speed, -_Time.x * speed));

                float4 col2 = tex2D(tex, uv + float2(_Time.x * speed * 0.5, _Time.x * 0.15 * speed));

                float4 col3 = tex2D(tex, uv + float2(_Time.x * speed * 0.84, -_Time.x * 0.11 * speed));

                float4 col4 = tex2D(tex, uv + float2(_Time.x * speed * 0.105, -_Time.x * 0.3515 * speed));

                return (col1 + col2 + col3 + col4) / 4;
            }

            // 输出结构>>>像素
            fixed4 frag (v2f i) : COLOR
            {
                //屏幕深度Z
                float ScreenZ = LinearEyeDepth(SAMPLE_DEPTH_TEXTURE_PROJ(_CameraDepthTexture, UNITY_PROJ_COORD(i.screenuv)));
                float4 finalCol = _Color;
                //Grab Tex
                fixed4 grabCol;
                grabCol = tex2D(_GrabPassTex, i.screenuv.xy / i.screenuv.w);
                //深色
                grabCol = lerp(grabCol, lerp(grabCol, _Color, _Color.a), _Opacity);


                fixed2 waveUV = i.uv.xy;
                return grabCol;
            }
            ENDCG
        }
    }
}