update method
Advances every live particle by dt seconds.
Implementation
@override
void update(ParticleStorage storage, double dt) {
var factor = 1.0 - coefficient * dt;
if (factor < 0.0) factor = 0.0;
final n = storage.aliveCount;
for (var i = 0; i < n; i++) {
storage.velX[i] *= factor;
storage.velY[i] *= factor;
storage.velZ[i] *= factor;
}
}