Barrel

ArrayList thingies = new ArrayList();
float grid, sz, theta;
int flip = -1;
int stepx = 20;
int stepy = stepx/5*3;
int column, row;
color bg = #555152 ;
color f1 = #2E2633  ;
color f2 = #99173C ;

void setup() {
  size(500, 300);
  background(bg);
  stroke(bg);
  column = width/stepx;
  row = height/stepy;
  sz = column -2;
  rectMode(CENTER);

  for (int y=0; y<height; y+=row) {
    flip *= -1;
    for (int x=0; x<width;x+=column) {
      Thingie thingie = new Thingie(x, y, flip, theta);
      thingies.add(thingie);
      flip *= -1;
      theta += TWO_PI/stepx;
    }
  }
}

void draw() {
  background(bg);

  for (int i=0; i<thingies.size();i++) {
    Thingie thing = (Thingie) thingies.get(i);
    thing.display();
  }


  if (frameCount % 4 == 0 && frameCount < 121) saveFrame("image-####.gif");
}


class Thingie {
  float edge, theta, theta2, x, y;
  int flip;

  Thingie(float _x, float _y, int _flip, float _theta) {
    x = _x;
    y = _y;
    flip = _flip;
    theta = _theta;
    theta2 = _theta;

  }

  void display() {
    fill(#ECE3B7);
    noStroke();
    //stroke(bg);
    edge = map(sin(theta), -1, 1, 0, .5*sz);

    if (flip == 1) {
      fill(f1);
    }
    else {
      fill(f2);
    }

    pushMatrix();
    translate(x+column/2, y+column/2);
    rotate(theta2);
    rect(0, 0, sz, sz, edge);
    popMatrix();
    theta -= 0.0523;
    theta2 -= (0.0523);
  }
}