import { EasingFunction } from "../easing";
import { Module, ModuleObject } from "../module";
import { ParticleEffect } from "../particleEffect";
import { Particle } from "../particle";
declare type ParticleWithInitialAlpha = Particle & {
    /**
     * Saved initial alpha of particle. This is cached when particle is added.
     */
    _alphaOverLifetime_initialAlpha?: number;
};
/**
 * Module that decays particles alpha over their lifetime.
 *
 * Alpha animation can be customized with `easing` property.
 *
 * This module modifies `Particle.alpha` property and can not be combined with any other modifier that does so.
 * It can however be combined with modules that alter the alpha during initialization, but these modules must be defined before `AlphaOverLifetime`!
 *
 * @module
 * @category    Modifier
 * easing {
 *      @tooltip        TODO
 *      @type           EasingFunction
 *      @defaultValue   easeOutSine
 * }
 */
export declare class AlphaOverLifetime extends Module {
    /**
     * Easing function that controls the animation of alpha.
     *
     * Assign via `EasingFunctions` export.
     */
    easing: EasingFunction;
    init(): void;
    handleParticleAdd: (particle: ParticleWithInitialAlpha) => void;
    update(dt: number): void;
    /**
     * Wrap the properties of the module into a JSON containing only primitive JavaScript data types
     * (such as numbers, strings, etc.) that can be serialized into strings natively.
     */
    toObject(): ModuleObject;
    static fromObject(particleEffect: ParticleEffect, object: ModuleObject, hideWarnings: boolean): AlphaOverLifetime;
    /**
     * Serializable identifier for the module.
     *
     * This must be unique between all existing Modules in the library.
     */
    static moduleTypeId: string;
}
export {};