Did you see this effect - tail after fast moving heroes' weapons? How to make this thing?
I believe that would be done with a slow moving particle emitter that has a short life span. that way it would always be created but only show if the hero is moving fast enough for it to drag behing
Actually, I think he's thinking of "ribbons."
Ribbons are what are used by on the blademaster and paladin's attack animations. For more information, a search of the website for the term "ribbons" would probably help.
The answer is blizz ribbons which comes with warcraft art tools but only worx with 3ds max 4 - 5.1 There might b a way to do it with gmax but thats about it i guess. Good Luck!!!
W00t! DexScript is coming out soon with a new version that will support ribbon emitters. - They say only a few weeks till they're done, and they're usually pretty accurate. GO DEX! W00t!