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Daily Creative Coding

元「30 min. Processing」。毎日、Creative Codingします。

ベクトル計算によるパーティクルの壁面での反射

/**
* reflection of a particle
*
* @author aa_debdeb
* @date 2016/12/30
*/

int COUNT = 200;

PVector loc, vel;
float circleR = 30;

void setup(){
  size(500, 500);
  noStroke();
  initialize();
}

void initialize(){
  loc = new PVector(width / 2, height / 2);
  float velSize = 10;
  float velAng = random(TWO_PI);
  vel = new PVector(velSize * cos(velAng), velSize * sin(velAng));
}

void draw(){
  if(frameCount % COUNT == COUNT - 1){
    initialize();
  }
  background(#CAE7F2);
  fill(#A52175, map(frameCount % COUNT, 0, COUNT - 1, 255, 0));
  float r = float(frameCount % COUNT) / COUNT < 0.1 ? map(float(frameCount % COUNT) / COUNT, 0, 0.1, 0, circleR): circleR;
  ellipse(loc.x, loc.y, r * 2, r * 2);
  loc.add(vel);
  PVector n = null;
  if(loc.x < circleR){
    reflect(new PVector(1, 0));
  }
  if(loc.x > width - circleR){
    reflect(new PVector(-1, 0));
  }
  if(loc.y < circleR){
    reflect(new PVector(0, 1));
  }
  if(loc.y > height - circleR){
    reflect(new PVector(0, -1));
  }
}

void reflect(PVector n){
  PVector vn = PVector.mult(n, PVector.dot(vel, n)); 
  PVector vt = PVector.sub(vel, vn);
  vel = PVector.add(PVector.mult(vn, -1), vt);
  loc.add(vel);  
}
f:id:aa_debdeb:20161227073527j:plain