for (int i=0; i<90; i++) {
    beginShape();
    for (int j=0; j<1000; j++) {
      // linear eq for increasing period:
      float period = .098*j + 30;
      // calculate wave height at current point:
      float sinHeight = -sin(((float)j/period)*PI);
      // draw point:
      vertex(j,40 + i*spacing + sinHeight*amplitude);
    }
    endShape();
  }