apply perlin noise
Applies the Perlin noise to the bitmap data, offsetting the octave displacement by the FLICKER_RATE each time this method is called. 

  
                  private function applyNoise():void {
                          _perlinNoise.perlinNoise(
                                  20,
                                  20,
                                  1,
                                  _perlinSeed,
                                  false,
                                  true,
                                  BitmapDataChannel.RED,
                                  true,
                                  _perlinOffsets
                          );
                          // altering offset contributes to upward animation of flames
                          (_perlinOffsets[0] as Point).y += FLICKER_RATE;
                  }