花びら

/**
* Petals
*
* @author aa_debdeb
* @date 2015/11/18
*/


ArrayList<Flow> flows;

void setup(){
  size(500, 500);
  smooth();
  frameRate(60);
  background(255, 240, 245);
  flows = new ArrayList<Flow>();
}

void draw(){
  noStroke();
  fill(255, 240, 245, 10);
  rect(-1, -1, width, height);
  if(random(1) < 0.5){
    flows.add(new Flow());
  }
  
  ArrayList<Flow> killedFlows = new ArrayList<Flow>();
  for(Flow flow : flows){
    flow.display();
    if(flow.isKilled()){
      killedFlows.add(flow);
    }
  }
  for(Flow killedFlow : killedFlows){
    flows.remove(killedFlow);
  }
  
}

class Flow{
  
  PVector pos;
  PVector velocity;
  float weight;
  float weightSpeed;
  float time;
  
  Flow(){
    pos = new PVector(random(width), random(height));
    float radian = random(TWO_PI);
    velocity = new PVector(1.0 * cos(radian), 1.0 * sin(radian));
    weight = 0.1;
    weightSpeed = 1.0;
  }  
  
  void display(){
    weightSpeed += - sqrt(time) * 0.005;
    weight += weightSpeed;
    if(weight < 0){weight = 0;}
    float forceSize = random(0.1);
    float radian = random(TWO_PI);
    PVector force = new PVector(forceSize * cos(radian), forceSize * sin(radian));
    velocity.add(force);
    PVector nextPos = PVector.add(pos, velocity); 
    stroke(218, 112, 214);
    strokeWeight(weight);
    line(pos.x, pos.y, nextPos.x, nextPos.y);
    pos = nextPos;
    time++;
  }
  
  boolean isKilled(){
    return weight == 0;
  }
}