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particle-curve overview

Table of contents

utils

ParticleCurve (type alias)

A value over a particle's normalized age t (0 = spawn, 1 = death; always 0 for a particle with an infinite lifetime). Forms:

  • a number: constant;
  • number[]: keyframes spread evenly from t = 0 to t = 1, linearly interpolated ([1, 0] fades from 1 to 0, [0, 1, 0] rises and falls);
  • ParticleKeyframe[]: keyframes at given t (sorted ascending), linearly interpolated, held before the first and after the last;
  • { keyframes, interpolation: 'step' }: either keyframe form, each value held until the next keyframe instead of interpolated - a lookup table of an old game ('linear' is the default). With number[] keyframes every value gets an equal share of the life ([a, b, c] shows a for the first third, c for the last), unlike the linear spread where the last value sits at t = 1;
  • a function (t, particle) => number, for anything else.

Signature

export type ParticleCurve =
  | number
  | readonly number[]
  | readonly ParticleKeyframe[]
  | {
      readonly keyframes: readonly number[] | readonly ParticleKeyframe[]
      readonly interpolation?: 'linear' | 'step'
    }
  | ParticleCurveFunction

ParticleCurveFunction (type alias)

A function curve: any value from the normalized age and the particle itself.

Signature

export type ParticleCurveFunction = (t: number, particle: Particle<any, any>) => number

ParticleKeyframe (type alias)

A keyframe of a {@link ParticleCurve}: value at normalized age t (0 = spawn, 1 = death).

Signature

export type ParticleKeyframe = { readonly t: number; readonly value: number }

evaluateParticleCurve

The value of curve at normalized age t. An undefined curve is 1, so it can multiply a particle's own value unconditionally.

Signature

export declare function evaluateParticleCurve(
  curve: ParticleCurve | undefined | null,
  t: number,
  particle: Particle<any, any>
): number