flash actionscript

import flash.filters.*;
import flash.display.*;
//
var my_btm = new BitmapData(200, 200, true, 0xFFFFFF);
gradient_mc.start_offset = [];
gradient_mc.finish_offset = [];
var c = 0;
while (c<3) {
 gradient_mc.start_offset[c] = {x:0, y:0};
 gradient_mc.finish_offset[c] = {x:Math.random()*4-2, y:Math.random()*3+4};
 c++;
}
//
gradient_mc.onEnterFrame = function() {
 var c = 0;
 while (c<3) {
  this.start_offset[c].x += this.finish_offset[c].x;
  this.start_offset[c].y += this.finish_offset[c].y;
  c++;
 }
 //
 my_btm.perlinNoise(15, 50, 3, 5, false, false, 1, true, this.start_offset);
 var dmf = new DisplacementMapFilter(my_btm, new flash.geom.Point(0, 0), 1, 1, 10, 200, "clamp");
 this.filters = [dmf];
};