American Flag

The American flag shown here was generated completely algorithmically using the dynamic drawing routines. As a result, the movie is very small - only about 1k!

The flag is divided up into narrow vertical strips using masks. Then the strips are rotated slightly using sin waves. This produces apparent motion in both the x and y directions.

The motion propagates from the left edge of the flag to the right edge, producing the effect that the wind is blowing from the left.

The function that animates the flag reads as follows:

function myWaveFlag(evt)
{
  for (var i = kNbrStrips-1; i>0; --i) {
    flags[i].rotation = flags[i-1].rotation;
  }
  var t = getTimer();
  flags[0].rotation = Math.sin(t*.001+Math.cos(t*.0005)*Math.PI*2)*2;
}

The next movie in this sequence shows how to apply this effect to a photographic image.