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Interval actions

Interval actions run for a fixed duration (in milliseconds) and then mark themselves done. They are the building blocks for tweens and for steps inside sequence().

Minimal example​

Runnable sample: website/snippets/actions/interval-actions.ts.

import { moveBy, moveTo, rotateBy, delay, callFunc, fadeOpacity, sequence } from '@zylem/game-lib/actions';

entity.runAction(
	sequence(
		moveBy({ x: 4, duration: 800 }),
		delay(300),
		rotateBy({ y: 180, duration: 500 }),
		callFunc(() => {
			entity.runAction(fadeOpacity({ from: 1, to: 0.3, duration: 400 }));
		}),
		moveTo({ x: 0, y: 0, z: 0, duration: 1000 }),
	),
);

Factories​

FunctionEffect
moveBy({ x?, y?, z?, duration })Displacement over time via velocity intent
moveTo({ x, y, z, duration })Absolute position; displacement computed on first tick
rotateBy({ x?, y?, z?, duration })Euler delta in degrees, applied as angular velocity
delay(ms)No-op wait
callFunc(fn)Runs fn once, completes immediately
fadeOpacity({ from?, to?, duration, targets?, restoreOpaque? })Lerps material opacity on meshes under the entity
resetEntityOpacity(entity, opacity?, transparent?)Instant opacity reset (not an Action)

moveBy and moveTo use setVelocityIntent with mode add so parallel moves compose within the same frame. rotateBy accumulates into transformStore.angularVelocity.

Opacity notes​

  • fadeOpacity traverses entity.group or entity.mesh unless you pass targets.
  • Materials must expose opacity and transparent. The action forces transparent: true while fading.
  • With restoreOpaque: true and to >= 1, opaque materials are restored when the fade completes.

Pitfalls​

  • moveTo captures the starting position on its first tick after reset(); restarting the same action instance recomputes from the new position.
  • Zero or negative duration skips motion for move/rotate helpers.
  • callFunc inside sequence is the usual place for spawning entities or playing sound; keep heavy work out of onTick implementations you write yourself.

API reference​