One of the toughest things to animate in Flash are large quantities of objects, like rain, sleet, dust, snow, or any other particle. A lot of animators will just create a "sheet" or large symbol of rain for example, and then motion tween that across the stage. This works, but the rain is all moving at the same speed, and over time, the viewer will begin to see a loop or repitiveness to the animation. The CartoonSmart Rain and Particles tutorial teaches how to programmably create independent particles of any type. With some simple changes to the code, the particles can change pace, direction , density, speed, distance, color, rotation, or alpha. And the particles can also have a finishing animation. For example, when the Flash animated rain particle hits the ground plane this can then trigger the rain particle symbol to splash. Likewise, the tutorial also teaches how to create a firework explode. The movieclip symbol shoots into the air, then when the actionscript animation finishes getting from point A to point B, the symbol advances to a frame where it explodes. Flash Examples on the site are
Floating Crystal Particles
,
Swirling Leaves
, Rain Snow or Sleet (seen above),
Chaotic Particles,
Fireworks.
A good companion tutorial is the
Flash Fire tutorial.