Sin for ever

int nbLines = 10, nbPts = 80;

float h, step;

float[] periods = new float[nbLines];

float[] speeds = new float[nbLines];

float[] offsets = new float[nbLines];

float[] amplitudes = new float[nbLines];

float [] prevys = new float[nbPts+1];

​

void setup() {

  size(450, 450, P2D);

  noFill();

  colorMode(HSB, 1);

  strokeWeight(8);

  step = width / float(nbPts);

  mousePressed();

}

​

void draw() {

  background(1);

  for (int i = 0; i < nbLines; i++) {

    offsets[i] += speeds[i];

    beginShape();

    stroke(0);

    for (int j = 0; j <= nbPts; j++) {

      float x = step * j;

      float y;

      if (i == 0) {

        y = i * 2 * h + h * sin(offsets[i] + float(j)/periods[i]) + h;

      } else {

        y = max(prevys[j] + 10, i * 2 * h + amplitudes[i] * sin(offsets[i] + float(j)/periods[i]) + h);

      }

      prevys[j] = y;

      vertex(x, y);

    }

    endShape();

  }

}

​

void mousePressed() {

  nbLines = (int)random(5, 10);

  h = height / nbLines / 2;

  for (int i = 0; i < nbLines; i++) {

    periods[i] = random(12, 102);

    speeds[i] = random(.05, .15) * (i%2 == 0 ? 1 : -1);

    offsets[i] = random(123);

    amplitudes[i] = random(2, .5) * h;

  }

}