1681-engine / index / AnimStateMachine

Class: AnimStateMachine<State, Clip, P>

Defined in: src/anim/AnimStateMachine.ts:45

Chooses which clip an Animator plays from named states and the transitions between them, the way an animation graph in a larger engine does: the game sets parameters (a bool, a number, a one-shot trigger) and the machine moves between states when a transition's conditions hold, when a clip has played through, or from any state at all by priority. Frame markers fire events (a footstep on frame 3) for the game to hang sounds and effects on.

Pure and driven by update(dt), so it runs under node with a fake clock. The definition is compiled into typed arrays once; an update allocates nothing.

const sm = new AnimStateMachine(sheet.clips, {
  initial: 'idle',
  params: { speed: 0, grounded: true, jump: 'trigger' },
  states: { idle: { clip: 'idle' }, run: { clip: 'run', markers: [{ frame: 2, name: 'step' }] }, jump: { clip: 'jump' } },
  transitions: [
    { from: 'idle', to: 'run', when: { speed: ['>', 0] } },
    { from: 'run', to: 'idle', when: { speed: 0 } },
    { from: '*', to: 'jump', when: { jump: true, grounded: true }, priority: 10 },
  ],
});
sm.onEvent = (name) => name === 'step' && sound.play('step');
sm.set('speed', 3);
sm.update(dt);              // seconds; then show sm.frame

Type Parameters

Type Parameter	Default type
State extends string	string
Clip extends string	string
P extends AnimParams	AnimParams

Constructors

Constructor

new AnimStateMachine<State, Clip, P>(clips, options): AnimStateMachine<State, Clip, P>;

Defined in: src/anim/AnimStateMachine.ts:61

Parameters

Parameter	Type
clips	Record<Clip, AnimationClip>
options	AnimStateMachineOptions<State, Clip, P>

Returns

AnimStateMachine<State, Clip, P>

Properties

animator

readonly animator: Animator<Clip>;

Defined in: src/anim/AnimStateMachine.ts:47

The animator it drives; read frame off it (or off the machine).

---

onEvent

onEvent: ((event, state, frame) => void) | null = null;

Defined in: src/anim/AnimStateMachine.ts:49

Fired for every marker playback reaches, the state's first frame's on entering it.

---

onStateChange

onStateChange: ((from, to) => void) | null = null;

Defined in: src/anim/AnimStateMachine.ts:51

Fired after each change of state.

Accessors

frame

Get Signature

get frame(): string | number;

Defined in: src/anim/AnimStateMachine.ts:78

The frame to show now (a sheet frame index or name, as the clip lists it).

Returns

string | number

---

normalizedTime

Get Signature

get normalizedTime(): number;

Defined in: src/anim/AnimStateMachine.ts:83

How much of this state's clip has played: 0 at entry, 1 after one pass, 2 after two loops.

Returns

number

---

state

Get Signature

get state(): State;

Defined in: src/anim/AnimStateMachine.ts:73

The state playing.

Returns

State

Methods

get()

get(name): number | boolean;

Defined in: src/anim/AnimStateMachine.ts:96

A parameter's value: bools as booleans, triggers as whether they are set.

Parameters

Parameter	Type
name	keyof P & string

Returns

number | boolean

---

play()

play(state): this;

Defined in: src/anim/AnimStateMachine.ts:114

Goes to state now, whatever the transitions say (a respawn, a cut scene).

Parameters

Parameter	Type
state	State

Returns

this

---

resetParams()

resetParams(): this;

Defined in: src/anim/AnimStateMachine.ts:122

Back to the initial values of every parameter (triggers cleared).

Returns

this

---

resetTrigger()

resetTrigger(name): this;

Defined in: src/anim/AnimStateMachine.ts:108

Parameters

Parameter	Type
name	keyof P & string

Returns

this

---

set()

set(name, value): this;

Defined in: src/anim/AnimStateMachine.ts:88

Sets a bool or number parameter.

Parameters

Parameter	Type
name	keyof P & string
value	number | boolean

Returns

this

---

trigger()

trigger(name): this;

Defined in: src/anim/AnimStateMachine.ts:103

Fires a trigger: the next update's transitions see it once.

Parameters

Parameter	Type
name	keyof P & string

Returns

this

---

update()

update(dt): void;

Defined in: src/anim/AnimStateMachine.ts:131

Advances the clip by dt seconds, fires the markers it passed, then takes at most one transition (so a chain of them never runs through several states in one frame). update(0) only checks the transitions.

Parameters

Parameter	Type
dt	number

Returns

void