In this lesson, you will learn how round-trip time (RTT) and network jitter directly influence player responsiveness and the techniques used to mask these inconsistencies in a multiplayer environment.
The Impact of Latency and Jitter
In multiplayer Unity development, Latency (or RTT) is the time it takes for a packet to travel from the client to the server and back. It is essentially the "ping" of your game. However, even if your average latency is low, Jitter—the variation in the time it takes for consecutive packets to arrive—can be destructive. High jitter leads to "choppy" movement, as the game client receives updates at inconsistent intervals, causing entities to teleport or "rubber-band" because the simulation cannot predict their next position reliably.
Strategies for Mitigation
To maintain a responsive feel despite these network realities, we utilize Client-Side Prediction and Entity Interpolation.
- Client-Side Prediction: The local client simulates its own actions immediately without waiting for server confirmation. If the server later sends a position that disagrees with the client's local calculation, the client must reconcile the state.
- Entity Interpolation: To counter jitter, we don't render remote players at their exact "last received" position. Instead, we buffer incoming packets and interpolate between them to ensure smooth motion.
Consider a simple movement buffer implementation for a remote entity:
// Smoothly move the entity towards the target position received from the server
void Update() {
float interpolationFactor = Time.deltaTime * interpolationSpeed;
transform.position = Vector3.Lerp(transform.position, targetPosition, interpolationFactor);
}
By using Vector3.Lerp or Vector3.MoveTowards, we smooth out the arrival of packets. If the connection is jittery, the interpolationSpeed determines how aggressively the game tries to catch up versus how much it favors smooth visual movement. Increasing the buffer delay adds latency but effectively hides jitter-induced stutter, a classic trade-off in network architecture.
Key Takeaway: Latency dictates the delay in your game's feedback loop, while jitter creates inconsistent movement; mitigating these requires balancing immediate client-side feedback with interpolation to smooth out the inevitable irregularities of network traffic.