Shader "Custom/Loading"
{
 Properties
 {
 _Color ("Color", Color) = (0, 1, 0, 1)
 _Speed ("Speed", Range(1, 10)) = 1
 _Radius ("Radius", Range(0, 0.5)) = 0.3
 }
 SubShader
 {
 Tags { "Queue" = "Transparent" }
 Blend SrcAlpha OneMinusSrcAlpha
 ZWrite Off
 
 Pass
 {
  CGPROGRAM
  #pragma vertex vert
  #pragma fragment frag
  #include "UnityCG.cginc"
 
  #define PI 3.14159
 
  struct appdata
  {
  float4 vertex : POSITION;
  float2 uv : TEXCOORD0;
  };
 
  struct v2f
  {  
  float4 vertex : SV_POSITION;
  float2 uv : TEXCOORD0;
  };
 
  fixed4 _Color;
  half _Speed;
  fixed _Radius;
 
  fixed4 circle(float2 uv, float2 center, float radius)
  {
  //if(pow(uv.x - center.x, 2) + pow(uv.y - center.y, 2) < pow(radius, 2)) return _Color;
 
  if(length(uv - center) < radius) return _Color;
  else return fixed4(0, 0, 0, 0); 
  }
 
  v2f vert (appdata v)
  {
  v2f o;
  o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
  o.uv = v.uv;
 
  return o;
  }
  
  fixed4 frag (v2f i) : SV_Target
  {
  fixed4 finalCol = (0, 0, 0, 0);
 
  for(int count = 7; count > 1; count--)
  {
   half radian = fmod(_Time.y * _Speed + count * 0.5, 2 * PI);//弧度
   half2 center = half2(0.5 - _Radius * cos(radian), 0.5 + _Radius * sin(radian)); 
 
   finalCol += circle(i.uv, center, count * 0.01);
  }
 
  return finalCol;
  }
  ENDCG
 }
 }
}

Shader "Custom/Cooling"
{
 Properties
 {
 _MainTex ("Texture", 2D) = "white" {}
 _Speed ("Speed", Range(1, 10)) = 1
 _Color ("Color", Color) = (0, 0, 0, 1)
 }
 SubShader
 { 
 Pass
 {
  CGPROGRAM
  #pragma vertex vert
  #pragma fragment frag
  #include "UnityCG.cginc"
 
  #define PI 3.142
 
  struct appdata
  {
  float4 vertex : POSITION;
  float2 uv : TEXCOORD0;
  };
 
  struct v2f
  {  
  float4 vertex : SV_POSITION;
  float2 uv : TEXCOORD0;
  };
 
  sampler2D _MainTex;
  float4 _MainTex_ST;
  half _Speed;
  fixed4 _Color;
 
  v2f vert (appdata v)
  {
  v2f o;
  o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
  o.uv = TRANSFORM_TEX(v.uv, _MainTex);
  return o;
  }
  
  fixed4 frag (v2f i) : SV_Target
  {
  fixed4 col = tex2D(_MainTex, i.uv);
 
  //以正中間為中心，所以將uv范圍映射到(-0.5, 0.5)
  float2 uv = i.uv - float2(0.5, 0.5);
  //atan2(y, x)：反正切，y/x的反正切范圍在[-π, π]內(nèi)
  //-1用于控制方向
  float radian = atan2(uv.y, uv.x) * -1 + PI;
 
  float2 radian2 = fmod(_Time.y * _Speed, 2 * PI);
  fixed v = step(radian, radian2);
 
  if(v > 0) return col;
  else return col * _Color;
  }
  ENDCG
 }
 }
}