円を脈動させる

/**
* Expanding Circle
*
* @author aa_debdeb
* @date 2015/09/18
*/

float RADIOUS = 150;
float RADOUS_VARIANT = 100;

float TIME_STEP = 0.01;
float time = 0.0;

void setup(){
  size(500, 500);
  smooth();
  frameRate(24);
  noStroke();
  background(255);
}

void draw(){
  background(255);
  fill(220, 20, 60);
  float radious = getRadious();
  arc(width / 2.0, height / 2.0, 2.0 * radious, 2.0 * radious, 0, PI * 2);

  time += TIME_STEP;
}

float getRadious(){
  return RADIOUS + RADOUS_VARIANT *((1.0 + sin(time * 2.0)) * 0.5) * sin(time * 20.0);
}