1681-engine / index / LagCompensator

Class: LagCompensator

Defined in: src/net/LagCompensator.ts:35

Lag compensation for a server: where every body was a moment ago, so a shot is judged against what the shooter saw. A client draws other bodies delayMs in the past between two snapshots (InterpolationBuffer); the server records the same positions at the same times, when each snapshot goes out, and blends between them the same way, so a rewind lands on the very picture the shooter aimed at, not on where the target has walked to since.

How far back a client may ask is capped (clampTime): a client that claims an old time to shoot round a corner gets no further back than maxRewindMs.

// when snapshots go out (RoomHost does this for a Room made with `rewindMs`)
lag.record(now, players);
// a client's shot, sent with `at: buffer.viewTime(serverNow())`
const at = LagCompensator.clampTime(msg.at, now, 250);
const hit = lag.alongRay(at, x, y, dx, dy, range, 6, shooterId)[0];

Constructors

Constructor

new LagCompensator(keepMs?): LagCompensator;

Defined in: src/net/LagCompensator.ts:39

keepMs: how much history is kept; at least the longest rewind allowed plus a snapshot interval.

Parameters

Parameter	Type	Default value
keepMs	number	1000

Returns

LagCompensator

Properties

keepMs

readonly keepMs: number = 1000;

Defined in: src/net/LagCompensator.ts:39

Accessors

newest

Get Signature

get newest(): number;

Defined in: src/net/LagCompensator.ts:42

The latest recorded time, or -Infinity before any.

Returns

number

---

oldest

Get Signature

get oldest(): number;

Defined in: src/net/LagCompensator.ts:46

Returns

number

Methods

all()

all(time): RewoundBody[];

Defined in: src/net/LagCompensator.ts:92

Every body in the history at time.

Parameters

Parameter	Type
time	number

Returns

RewoundBody[]

---

alongRay()

alongRay(
   time, 
   x, 
   y, 
   dx, 
   dy, 
   range, 
   radius, 
   except?
): RewoundHit[];

Defined in: src/net/LagCompensator.ts:115

A hitscan at time: the bodies a ray from (x, y) along (dx, dy) passed within radius of, before range px, in the order it met them. except (the shooter) is left out. Walls are the game's to check against the first hit.

Parameters

Parameter	Type
time	number
x	number
y	number
dx	number
dy	number
range	number
radius	number
except?	number

Returns

RewoundHit[]

---

at()

at(id, time): 
  | {
  x: number;
  y: number;
}
  | null;

Defined in: src/net/LagCompensator.ts:85

Where body id was at time, blended between the frames around it as InterpolationBuffer blends; null when the history has no frame of it. Before the oldest frame it is where it was then; after the newest, where it is.

Parameters

Parameter	Type
id	number
time	number

Returns

| { x: number; y: number; } | null

---

clear()

clear(): void;

Defined in: src/net/LagCompensator.ts:68

Returns

void

---

forget()

forget(id): void;

Defined in: src/net/LagCompensator.ts:64

Forgets a body everywhere in the history (it left the game, not just the view).

Parameters

Parameter	Type
id	number

Returns

void

---

near()

near(
   time, 
   x, 
   y, 
   radius, 
   except?
): RewoundBody[];

Defined in: src/net/LagCompensator.ts:106

The bodies whose centre was within radius of (x, y) at time, nearest first; except (the shooter) left out.

Parameters

Parameter	Type
time	number
x	number
y	number
radius	number
except?	number

Returns

RewoundBody[]

---

record()

record(time, bodies): void;

Defined in: src/net/LagCompensator.ts:51

Records every body's position at time. A time not after the last one recorded replaces that frame.

Parameters

Parameter	Type
time	number
bodies	Iterable<{ id: number; x: number; y: number; }>

Returns

void

---

clampTime()

static clampTime(
   claimed, 
   now, 
   maxRewindMs
): number;

Defined in: src/net/LagCompensator.ts:76

A time a client claims it saw, kept within [now - maxRewindMs, now]: the window a rewind is honoured in. A claim that is not a finite number is taken as now (no rewind).

Parameters

Parameter	Type
claimed	unknown
now	number
maxRewindMs	number

Returns

number