update method
Advances every live particle by dt seconds.
Implementation
@override
void update(ParticleStorage storage, double dt) {
final n = storage.aliveCount;
for (var i = 0; i < n; i++) {
final life = storage.lifetime[i];
final nAge = life > 0.0 ? storage.age[i] / life : 0.0;
storage.size[i] =
storage.baseSize[i] * scale.sample(nAge, storage.random01[i]);
}
}