Perticle Emitters: How to fade particles in from 0, then back out to 0

[Jake.Caron]

The title is the question.

[samme]

emitter.setAlpha(function (p, k, t) {
  return 1 - 2 * Math.abs(t - 0.5);
});

[jackfreak]

OMG you can pass functions !!! Thanks!