phaser/src/gameobjects/particles/Particle.js

/**
 * @author       Richard Davey <rich@photonstorm.com>
 * @copyright    2020 Photon Storm Ltd.
 * @license      {@link https://opensource.org/licenses/MIT|MIT License}
 */

var Class = require('../../utils/Class');
var DegToRad = require('../../math/DegToRad');
var DistanceBetween = require('../../math/distance/DistanceBetween');

/**
 * @classdesc
 * A Particle is a simple Game Object controlled by a Particle Emitter and Manager, and rendered by the Manager.
 * It uses its own lightweight physics system, and can interact only with its Emitter's bounds and zones.
 *
 * @class Particle
 * @memberof Phaser.GameObjects.Particles
 * @constructor
 * @since 3.0.0
 *
 * @param {Phaser.GameObjects.Particles.ParticleEmitter} emitter - The Emitter to which this Particle belongs.
 */
var Particle = new Class({

    initialize:

    function Particle (emitter)
    {
        /**
         * The Emitter to which this Particle belongs.
         *
         * A Particle can only belong to a single Emitter and is created, updated and destroyed via it.
         *
         * @name Phaser.GameObjects.Particles.Particle#emitter
         * @type {Phaser.GameObjects.Particles.ParticleEmitter}
         * @since 3.0.0
         */
        this.emitter = emitter;

        /**
         * The texture frame used to render this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#frame
         * @type {Phaser.Textures.Frame}
         * @default null
         * @since 3.0.0
         */
        this.frame = null;

        /**
         * The x coordinate of this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#x
         * @type {number}
         * @default 0
         * @since 3.0.0
         */
        this.x = 0;

        /**
         * The y coordinate of this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#y
         * @type {number}
         * @default 0
         * @since 3.0.0
         */
        this.y = 0;

        /**
         * The x velocity of this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#velocityX
         * @type {number}
         * @default 0
         * @since 3.0.0
         */
        this.velocityX = 0;

        /**
         * The y velocity of this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#velocityY
         * @type {number}
         * @default 0
         * @since 3.0.0
         */
        this.velocityY = 0;

        /**
         * The x acceleration of this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#accelerationX
         * @type {number}
         * @default 0
         * @since 3.0.0
         */
        this.accelerationX = 0;

        /**
         * The y acceleration of this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#accelerationY
         * @type {number}
         * @default 0
         * @since 3.0.0
         */
        this.accelerationY = 0;

        /**
         * The maximum horizontal velocity this Particle can travel at.
         *
         * @name Phaser.GameObjects.Particles.Particle#maxVelocityX
         * @type {number}
         * @default 10000
         * @since 3.0.0
         */
        this.maxVelocityX = 10000;

        /**
         * The maximum vertical velocity this Particle can travel at.
         *
         * @name Phaser.GameObjects.Particles.Particle#maxVelocityY
         * @type {number}
         * @default 10000
         * @since 3.0.0
         */
        this.maxVelocityY = 10000;

        /**
         * The bounciness, or restitution, of this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#bounce
         * @type {number}
         * @default 0
         * @since 3.0.0
         */
        this.bounce = 0;

        /**
         * The horizontal scale of this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#scaleX
         * @type {number}
         * @default 1
         * @since 3.0.0
         */
        this.scaleX = 1;

        /**
         * The vertical scale of this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#scaleY
         * @type {number}
         * @default 1
         * @since 3.0.0
         */
        this.scaleY = 1;

        /**
         * The alpha value of this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#alpha
         * @type {number}
         * @default 1
         * @since 3.0.0
         */
        this.alpha = 1;

        /**
         * The angle of this Particle in degrees.
         *
         * @name Phaser.GameObjects.Particles.Particle#angle
         * @type {number}
         * @default 0
         * @since 3.0.0
         */
        this.angle = 0;

        /**
         * The angle of this Particle in radians.
         *
         * @name Phaser.GameObjects.Particles.Particle#rotation
         * @type {number}
         * @default 0
         * @since 3.0.0
         */
        this.rotation = 0;

        /**
         * The tint applied to this Particle.
         *
         * @name Phaser.GameObjects.Particles.Particle#tint
         * @type {integer}
         * @webglOnly
         * @since 3.0.0
         */
        this.tint = 0xffffff;

        /**
         * The lifespan of this Particle in ms.
         *
         * @name Phaser.GameObjects.Particles.Particle#life
         * @type {number}
         * @default 1000
         * @since 3.0.0
         */
        this.life = 1000;

        /**
         * The current life of this Particle in ms.
         *
         * @name Phaser.GameObjects.Particles.Particle#lifeCurrent
         * @type {number}
         * @default 1000
         * @since 3.0.0
         */
        this.lifeCurrent = 1000;

        /**
         * The delay applied to this Particle upon emission, in ms.
         *
         * @name Phaser.GameObjects.Particles.Particle#delayCurrent
         * @type {number}
         * @default 0
         * @since 3.0.0
         */
        this.delayCurrent = 0;

        /**
         * The normalized lifespan T value, where 0 is the start and 1 is the end.
         *
         * @name Phaser.GameObjects.Particles.Particle#lifeT
         * @type {number}
         * @default 0
         * @since 3.0.0
         */
        this.lifeT = 0;

        /**
         * The data used by the ease equation.
         *
         * @name Phaser.GameObjects.Particles.Particle#data
         * @type {object}
         * @since 3.0.0
         */
        this.data = {
            tint: { min: 0xffffff, max: 0xffffff, current: 0xffffff },
            alpha: { min: 1, max: 1 },
            rotate: { min: 0, max: 0 },
            scaleX: { min: 1, max: 1 },
            scaleY: { min: 1, max: 1 }
        };
    },

    /**
     * Checks to see if this Particle is alive and updating.
     *
     * @method Phaser.GameObjects.Particles.Particle#isAlive
     * @since 3.0.0
     *
     * @return {boolean} `true` if this Particle is alive and updating, otherwise `false`.
     */
    isAlive: function ()
    {
        return (this.lifeCurrent > 0);
    },

    /**
     * Resets the position of this particle back to zero.
     *
     * @method Phaser.GameObjects.Particles.Particle#resetPosition
     * @since 3.16.0
     */
    resetPosition: function ()
    {
        this.x = 0;
        this.y = 0;
    },

    /**
     * Starts this Particle from the given coordinates.
     *
     * @method Phaser.GameObjects.Particles.Particle#fire
     * @since 3.0.0
     *
     * @param {number} x - The x coordinate to launch this Particle from.
     * @param {number} y - The y coordinate to launch this Particle from.
     */
    fire: function (x, y)
    {
        var emitter = this.emitter;

        this.frame = emitter.getFrame();

        if (emitter.emitZone)
        {
            //  Updates particle.x and particle.y during this call
            emitter.emitZone.getPoint(this);
        }

        if (x === undefined)
        {
            this.x += emitter.x.onEmit(this, 'x');
        }
        else
        {
            this.x += x;
        }

        if (y === undefined)
        {
            this.y += emitter.y.onEmit(this, 'y');
        }
        else
        {
            this.y += y;
        }

        this.life = emitter.lifespan.onEmit(this, 'lifespan');
        this.lifeCurrent = this.life;
        this.lifeT = 0;

        var sx = emitter.speedX.onEmit(this, 'speedX');
        var sy = (emitter.speedY) ? emitter.speedY.onEmit(this, 'speedY') : sx;

        if (emitter.radial)
        {
            var rad = DegToRad(emitter.angle.onEmit(this, 'angle'));

            this.velocityX = Math.cos(rad) * Math.abs(sx);
            this.velocityY = Math.sin(rad) * Math.abs(sy);
        }
        else if (emitter.moveTo)
        {
            var mx = emitter.moveToX.onEmit(this, 'moveToX');
            var my = (emitter.moveToY) ? emitter.moveToY.onEmit(this, 'moveToY') : mx;

            var angle = Math.atan2(my - this.y, mx - this.x);

            var speed = DistanceBetween(this.x, this.y, mx, my) / (this.life / 1000);

            //  We know how many pixels we need to move, but how fast?
            // var speed = this.distanceToXY(displayObject, x, y) / (maxTime / 1000);

            this.velocityX = Math.cos(angle) * speed;
            this.velocityY = Math.sin(angle) * speed;
        }
        else
        {
            this.velocityX = sx;
            this.velocityY = sy;
        }

        if (emitter.acceleration)
        {
            this.accelerationX = emitter.accelerationX.onEmit(this, 'accelerationX');
            this.accelerationY = emitter.accelerationY.onEmit(this, 'accelerationY');
        }

        this.maxVelocityX = emitter.maxVelocityX.onEmit(this, 'maxVelocityX');
        this.maxVelocityY = emitter.maxVelocityY.onEmit(this, 'maxVelocityY');

        this.delayCurrent = emitter.delay.onEmit(this, 'delay');

        this.scaleX = emitter.scaleX.onEmit(this, 'scaleX');
        this.scaleY = (emitter.scaleY) ? emitter.scaleY.onEmit(this, 'scaleY') : this.scaleX;

        this.angle = emitter.rotate.onEmit(this, 'rotate');
        this.rotation = DegToRad(this.angle);

        this.bounce = emitter.bounce.onEmit(this, 'bounce');

        this.alpha = emitter.alpha.onEmit(this, 'alpha');

        this.tint = emitter.tint.onEmit(this, 'tint');
    },

    /**
     * An internal method that calculates the velocity of the Particle.
     *
     * @method Phaser.GameObjects.Particles.Particle#computeVelocity
     * @since 3.0.0
     *
     * @param {Phaser.GameObjects.Particles.ParticleEmitter} emitter - The Emitter that is updating this Particle.
     * @param {number} delta - The delta time in ms.
     * @param {number} step - The delta value divided by 1000.
     * @param {array} processors - Particle processors (gravity wells).
     */
    computeVelocity: function (emitter, delta, step, processors)
    {
        var vx = this.velocityX;
        var vy = this.velocityY;

        var ax = this.accelerationX;
        var ay = this.accelerationY;

        var mx = this.maxVelocityX;
        var my = this.maxVelocityY;

        vx += (emitter.gravityX * step);
        vy += (emitter.gravityY * step);

        if (ax)
        {
            vx += (ax * step);
        }

        if (ay)
        {
            vy += (ay * step);
        }

        if (vx > mx)
        {
            vx = mx;
        }
        else if (vx < -mx)
        {
            vx = -mx;
        }

        if (vy > my)
        {
            vy = my;
        }
        else if (vy < -my)
        {
            vy = -my;
        }

        this.velocityX = vx;
        this.velocityY = vy;

        //  Apply any additional processors
        for (var i = 0; i < processors.length; i++)
        {
            processors[i].update(this, delta, step);
        }
    },

    /**
     * Checks if this Particle is still within the bounds defined by the given Emitter.
     *
     * If not, and depending on the Emitter collision flags, the Particle may either stop or rebound.
     *
     * @method Phaser.GameObjects.Particles.Particle#checkBounds
     * @since 3.0.0
     *
     * @param {Phaser.GameObjects.Particles.ParticleEmitter} emitter - The Emitter to check the bounds against.
     */
    checkBounds: function (emitter)
    {
        var bounds = emitter.bounds;
        var bounce = -this.bounce;

        if (this.x < bounds.x && emitter.collideLeft)
        {
            this.x = bounds.x;
            this.velocityX *= bounce;
        }
        else if (this.x > bounds.right && emitter.collideRight)
        {
            this.x = bounds.right;
            this.velocityX *= bounce;
        }

        if (this.y < bounds.y && emitter.collideTop)
        {
            this.y = bounds.y;
            this.velocityY *= bounce;
        }
        else if (this.y > bounds.bottom && emitter.collideBottom)
        {
            this.y = bounds.bottom;
            this.velocityY *= bounce;
        }
    },

    /**
     * The main update method for this Particle.
     *
     * Updates its life values, computes the velocity and repositions the Particle.
     *
     * @method Phaser.GameObjects.Particles.Particle#update
     * @since 3.0.0
     *
     * @param {number} delta - The delta time in ms.
     * @param {number} step - The delta value divided by 1000.
     * @param {array} processors - An optional array of update processors.
     *
     * @return {boolean} Returns `true` if this Particle has now expired and should be removed, otherwise `false` if still active.
     */
    update: function (delta, step, processors)
    {
        if (this.delayCurrent > 0)
        {
            this.delayCurrent -= delta;

            return false;
        }

        var emitter = this.emitter;

        //  How far along in life is this particle? (t = 0 to 1)
        var t = 1 - (this.lifeCurrent / this.life);

        this.lifeT = t;

        this.computeVelocity(emitter, delta, step, processors);

        this.x += this.velocityX * step;
        this.y += this.velocityY * step;

        if (emitter.bounds)
        {
            this.checkBounds(emitter);
        }

        if (emitter.deathZone && emitter.deathZone.willKill(this))
        {
            this.lifeCurrent = 0;

            //  No need to go any further, particle has been killed
            return true;
        }

        this.scaleX = emitter.scaleX.onUpdate(this, 'scaleX', t, this.scaleX);

        if (emitter.scaleY)
        {
            this.scaleY = emitter.scaleY.onUpdate(this, 'scaleY', t, this.scaleY);
        }
        else
        {
            this.scaleY = this.scaleX;
        }

        this.angle = emitter.rotate.onUpdate(this, 'rotate', t, this.angle);
        this.rotation = DegToRad(this.angle);

        this.alpha = emitter.alpha.onUpdate(this, 'alpha', t, this.alpha);

        this.tint = emitter.tint.onUpdate(this, 'tint', t, this.tint);

        this.lifeCurrent -= delta;

        return (this.lifeCurrent <= 0);
    }

});

module.exports = Particle;