A Zen master was out walking with his student. The student saw a fox chasing a rabbit and said to his master, "I wonder who will win?"
"According to an old fable," the master replied, "the rabbit will get away from the fox."
"Surely not, the fox is faster."
"But the rabbit will still escape," insisted the Zen master.
"Why are you so certain?" asked the student.
"Because the fox is running for his dinner, but the rabbit is running for his life."
http://chimera.labs.oreilly.com/books/1234000000802/ch05.html#driving_animation_with_requestanimationf http://stackoverflow.com/questions/20433474/dynamic-bones-animation-in-three-js