unit uCloud;

interface

type
 tCloudParticle = record
   x: real;
   y: real;
   size: real;
 end;

 tCloudGen = object
 private
   centerX, centerY: real;
   ms: real;
   mr: real;
   particles: array of tCloudParticle;
   procedure reborn(n: integer);
 public
   procedure init(x, y: real; n: integer; radius: real; max_size: real);
   function getParticle(n: integer): tCloudParticle;
   procedure reset(n: integer);
   procedure moveTo(x, y: real);
   procedure tick(quant: real);
   function count: integer;
 end;

const
 pix2 = pi * 2;
 third = 1 / 5;

implementation

{ tCloudGen }

function tCloudGen.count: integer;
begin
 result := high(particles) + 1;
end;

function tCloudGen.getParticle(n: integer): tCloudParticle;
begin
 result.x := 0;
 result.y := 0;
 result.size := 0;
 if n > high(particles) then exit;
 result := particles[n];
end;

procedure tCloudGen.init(x, y: real; n: integer; radius: real; max_size: real);
var
 i: integer;
begin
 moveTo(x, y);
 reset(n);
 ms := max_size;
 mr := radius;
 for i := 0 to n do
   tick(1);
end;

procedure tCloudGen.moveTo(x, y: real);
begin
 centerX := x;
 centerY := y;
end;

procedure tCloudGen.reborn(n: integer);
var
 a, r: real;
begin
 a := random * pix2;
 r := random * mr;
 particles[n].x := centerX + cos(a) * r;
 particles[n].y := centerY + sin(a) * r;
 particles[n].size := (random * 0.5 + 0.5) * ms;
end;

procedure tCloudGen.reset(n: integer);
var
 i: integer;
begin
 setLength(particles, n);
 n := high(particles);
 for i := 0 to n do begin
   //particles[i].size := 0;
   reborn(i);
   particles[i].size := sqr(random) * ms;
 end
end;

procedure tCloudGen.tick(quant: real);
var
 i, n: integer;
begin
 n := high(particles);
 for i := 0 to n do begin
   particles[i].size := particles[i].size * (1 - third * quant);
   if particles[i].size < 1
     then reborn(i);
 end;
end;

end.