Shader "Unlit/2D-Ocean"
{
 Properties
 {
 _MainTex ("Texture", 2D) = "white" {}
 _SunColor("SunColor",Color) = (1,1,1,1)
 _SunRoundColor("SunRoundColor",Color) = (1,0,0,1)
 _WaveColor1("WaveColor1",Color) = (1,1,1,1)
 _WaveColor2("WaveColor2",Color) = (1,1,1,1)
 _WaveColor3("WaveColor3",Color) = (1,1,1,1)
 _WaveColor4("WaveColor4",Color) = (1,1,1,1)
 _WaveColor5("WaveColor5",Color) = (1,1,1,1)
 _SkyColor("SkyColor",Color)=(0,1,0,1)
  _CloudPos1("CloudPos1",Vector)=(0,0,0,0)
 _CloudPos2("CloudPos2",Vector) = (0,0,0,0)
 _CloudPos3("CloudPos3",Vector) = (0,0,0,0)
 _CloudPos4("CloudPos4",Vector) = (0,0,0,0)
 _CloudPos5("CloudPos5",Vector) = (0,0,0,0)
 _WaveFactor1("WaveFactor1",Vector)=(0,0,0,0)
 _WaveFactor2("WaveFactor2",Vector) = (0,0,0,0)
 _WaveFactor3("WaveFactor3",Vector) = (0,0,0,0)
 _WaveFactor4("WaveFactor4",Vector) = (0,0,0,0)
 _WaveFactor5("WaveFactor5",Vector) = (0,0,0,0)
 _SunPos("SunPos",Vector)=(0,0,0,0)
 _SunRoundFactor("SunRoundFactor",Range(0.0,2.0)) = 0.1
 _SunSize("SunSize",Range(0.0,1.0)) = 1.0
 }
 SubShader
 {
 Tags { "RenderType"="Transparent" }
 LOD 100

 Blend SrcAlpha OneMinusSrcAlpha
 Pass
 {
 CGPROGRAM
 #pragma vertex vert
 #pragma fragment frag 
 #include "UnityCG.cginc"

 struct appdata
 {
 float4 vertex : POSITION;
 float2 uv : TEXCOORD0;
 };

 struct v2f
 {
 float2 uv : TEXCOORD0;
 float4 vertex : SV_POSITION;
 };

 sampler2D _MainTex;
 float4 _MainTex_ST;
 float4 _CloudPos1;
 float4 _CloudPos2;
 float4 _CloudPos3;
 float4 _CloudPos4;
 float4 _CloudPos5;
 float4 _WaveColor1;
 float4 _WaveColor2;
 float4 _WaveColor3;
 float4 _WaveColor4;
 float4 _WaveColor5;
 float4 _WaveFactor1;
 float4 _WaveFactor2;
 float4 _WaveFactor3;
 float4 _WaveFactor4;
 float4 _WaveFactor5;
 float4 _SunColor;
 float4 _SunRoundColor;
 float4 _SunPos;
 float _SunRoundFactor;
 float _SunSize;
 float4 _SkyColor;
 
 //畫單個圓(uv,位置，大小，抗鋸齒)
 float4 Circle(float2 uv, float2 center, float size, float blur) {
 uv = uv - center;
 uv = uv / size;
 float len = length(uv);
 //長度大于一個半徑單位透明度為0，小于透明度為1
 float val = smoothstep(1.0,1.0-blur, len);
 return float4(1, 1, 1, val);
 }

 //畫單個云
 float4 DrawCloud(float2 uv, float2 center, float size) {
 uv = uv - center;
 uv = uv / size;
 float4 col = Circle(uv, float2(0.0, 0.0), 0.2, 1);
 //將圓中不想要的部分剪切掉
 col = col * smoothstep(-0.1, -0.1 + 0.01, uv.y);
 //圓擺放不同位置組成云
 col += Circle(uv, float2(0.15, -0.05), 0.1, 1);
 col += Circle(uv, float2(0.0, -0.1), 0.11, 1);
 col += Circle(uv, float2(-0.15, -0.1), 0.1, 1);
 col += Circle(uv, float2(-0.3, -0.08), 0.1, 1);
 col += Circle(uv, float2(-0.2, 0.0), 0.15, 1);
 return col;
 }

 //畫復數云
 float4 DrawClouds(float2 uv) {
 uv.x += 0.03*_Time.y;
 //使得左右連續
 uv.x = frac(uv.x + 0.5) - 0.5;
 float4 col = DrawCloud(uv, _CloudPos1.xy, 0.1);
 col += DrawCloud(uv, _CloudPos2.xy, 0.12);
 col += DrawCloud(uv, _CloudPos3.xy, 0.14);
 col += DrawCloud(uv, _CloudPos4.xy, 0.16);
 col += DrawCloud(uv, _CloudPos5.xy, 0.18);
 return col;
 }

 //畫太陽光環
 float4 DrawSunCircle(float2 uv,float2 center,float size) {
 uv = uv - center;
 uv = uv / size;
 //atan2返回點(x,y)與x軸的夾角，范圍(-π,π]
 //獲取極坐標的θ角度
 float degree = atan2(uv.y , uv.x ) + _Time.y * -0.1;
 //uv向量離中心點距離
 //獲取極坐標的r=x2+y2開方
 float len = length(uv);
 //根據極坐標玫瑰線:r(θ)=a*sin(kθ)
 //求得r;a為擴散幅度，k為花瓣數*0.5
 float r = 0.3*abs(sin(degree*5.0));
 //畫花瓣
 //保留r值小于到中心點距離的所有像素
 float sunRound= smoothstep(r + 0.1 + _SunRoundFactor, r + _SunRoundFactor, len);
 return float4(1,1,1,sunRound)*_SunRoundColor;
 }

 //畫波浪(參數:uv,頻率,振幅,整體高度,移動速度)
 float4 DrawWave(float2 uv,float waveFrequency,float waveAmplitude,float waveHeight,float speed) {
 uv.x += speed * _Time.y;
 uv.y += sin(_Time.y+waveHeight)*0.02;
 //uv.y大于sin函數的部分透明度為0，小于的部分透明度為1
 float val = uv.y - sin(uv.x*waveFrequency)*waveAmplitude - waveHeight;
 val = smoothstep(0.001,0.0, val);
 return float4(1, 1, 1, val);
 }

 //畫背景
 float4 DrawBackground(float2 uv) {
 float4 val = lerp(float4(1,1,1,1), _SkyColor, uv.y);
 return val;
 }

 //混合圖層(b為前景,a為背景)
 float4 LerpImages(float4 a, float4 b) {
 return float4(lerp(a, b, b.a).rgb, a.a + b.a);
 }

 v2f vert (appdata v)
 {
 v2f o;
 o.vertex = UnityObjectToClipPos(v.vertex);
 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
 return o;
 }
 
 float4 frag (v2f i) : SV_Target
 { 
 //太陽中心
 float4 sunCoreColor = Circle(i.uv, _SunPos.xy, _SunSize, 0.05)*_SunColor;
 //太陽光環
 float4 sunAroundColor = DrawSunCircle(i.uv, _SunPos.xy, _SunSize);
 //云
 float4 cloudsColor = DrawClouds(i.uv);
 //波浪
 float4 wave1 = DrawWave(i.uv, _WaveFactor1.x, _WaveFactor1.y, _WaveFactor1.z, _WaveFactor1.w)*_WaveColor1;
 float4 wave2 = DrawWave(i.uv, _WaveFactor2.x, _WaveFactor2.y, _WaveFactor2.z, _WaveFactor2.w)*_WaveColor2;
 float4 wave3 = DrawWave(i.uv, _WaveFactor3.x, _WaveFactor3.y, _WaveFactor3.z, _WaveFactor3.w)*_WaveColor3;
 float4 wave4 = DrawWave(i.uv, _WaveFactor4.x, _WaveFactor4.y, _WaveFactor4.z, _WaveFactor4.w)*_WaveColor4;
 float4 wave5 = DrawWave(i.uv, _WaveFactor5.x, _WaveFactor5.y, _WaveFactor5.z, _WaveFactor5.w)*_WaveColor5;
 //背景
 float4 backgroundColor = DrawBackground(i.uv);
 //圖層疊加
 float4 finalColor = LerpImages(backgroundColor, sunAroundColor);
 finalColor = LerpImages(finalColor, sunCoreColor);
 finalColor= LerpImages(finalColor, wave1);
 finalColor = LerpImages(finalColor, wave2);
 finalColor = LerpImages(finalColor, wave3);
 finalColor = LerpImages(finalColor, wave4);
 finalColor = LerpImages(finalColor, wave5);
 finalColor = LerpImages(finalColor, cloudsColor);
 return finalColor;
 }
 ENDCG
 }
 }
}