update method
Advances every live particle by dt seconds.
Implementation
@override
void update(ParticleStorage storage, double dt) {
final ax = acceleration.x * dt;
final ay = acceleration.y * dt;
final az = acceleration.z * dt;
final n = storage.aliveCount;
for (var i = 0; i < n; i++) {
storage.velX[i] += ax;
storage.velY[i] += ay;
storage.velZ[i] += az;
}
}