PHASER3 - SCROLLING CAMERA CLASS

ScrollingCamera extends the class Phaser.Cameras.Scene2D.Camera of Phaser 3 framework, adding the capacity of vertical and horizontal scrolling by dragging or using the mouse wheel, with optional snap system.
The scroll is customizable.

Live demo: https://jjcapellan.github.io/Phaser3-ScrollingCamera/

Features

• Vertical or horizontal scroll
• Natural snap effect (customizable)
• Snap event (sends the snap position)
• Interactive, even behind other cameras.
• Accepts dragging and mouse wheel as input (keyboard supported).

Table of contents

• Installation
  • Browser
  • From NPM
• How to use
• Snap event
• Public methods
  • setSpeed
  • moveToSanap
• Public properties
  • snapIndex
• License

Installation

Browser

There are two alternatives:

• Download the file scrollcam.umd.js to your proyect folder and add a reference in your html:

<script src = "scrollcam.umd.js"></script>

• Point a script tag to the CDN link:

<script src = "https://cdn.jsdelivr.net/gh/jjcapellan/[email protected]/dist/scrollcam.umd.js"></script>

Important: the class is exposed as ScrollingCamera

From NPM

npm i phaser3-scrolling-camera

Then you can acces the class as:

• CommonJS module:

const Phaser = require('phaser');
const ScrollingCamera = require('phaser3-scrolling-camera').default;

// In scene.create function
const config = { ... }
const myScrollCam = new ScrollingCamera(this, config);

• ES6 module:

import Phaser from 'phaser';
import ScrollingCamera from 'phaser3-scrolling-camera';

// In scene.create function
const config = { ... }
const myScrollCam = new ScrollingCamera(this, config);

How to use

This is the simplest case (uses the default parameters):

// In create function ...
let myCamera = new ScrollingCamera(this);

The constructor of ScrollingCamera only needs as argument a scene object. All the other arguments are optionals.
And this is the opposite case with all possible customizations:

// In create function ...
let cameraOptions = {
      x: 50,             // x position of the camera (default = 0)
      y: 50,             // y position of the camera (default = 0)
      width: 300,        // Width of the camera (default = game.config.width)
      height: 500,       // Height of the camera (default = game.config.height)
      contentBounds: {   // Determines the limits of the area where the camera is looking. (optional)
        x: 400,          // x position of contents from top-left origin (default = cameraOptions.x)
        y: 10,           // y position of contents from top-left origin (default = cameraOptions.y)
        length: 1200     // Distance measured in pixels along the camera main axis
      },
      wheel: {           // Mouse wheel params (optional)
        enable: true,    // Does this camera use the mouse wheel? (default = false)
        delta: 60        // Variation of scroll in pixels with each wheel change (default = 55)
      },
      drag: 0.90,        // Reduces the scroll speed per game step in 10%. (default = 0.95)      
      snap: {
        enable: false,   // Does this camera use snap effect? (default = false)
        padding: 20,     // Gap in pixels between snaps (default = 20)
        bounces: 3       // Number of bounces on target before the snap (default = 3)
      },
      horizontal: true   // Does this camera use horizontal scroll (default = false)
    };
const myCamera = new ScrollingCamera(this, cameraOptions);

In this image the content for the ScrollingCamera camera is positioned out of screen, in this way we haven't to hide it to the main camera of the scene (camera.ignore(...)):

Snap event

In the code bellow, the event snap returns the last snap position (snapIndex) where the camera was stopped.
This position is not in pixels, is an index representing the first snap, the second snap, ... (0, 1, ...).
This is usefull to extract a numeric value like in the demo.

const myCamera = new ScrollingCamera(this, configObject)

myCamera.on('snap', (snapIndex) => {
  console.log(snapIndex);
});

Public methods

Besides the functions inherited from the parent class, ScrollingCamera have these public methods:

setSpeed(speed: number)

Params:

• speed : scroll speed in pixels/second

This method can be usefull, for example, to implement keyboard control:

// In create function ...
let myCamera = new ScrollingCamera(this);
let cursors = this.input.keyboard.createCursorKeys();
cursors.down.on('down', () => myCamera.setSpeed(50));
cursors.up.on('down', () => myCamera.setSpeed(-50));

moveToSnap(snapIndex: number)

Params:

• snapIndex {number}: Snap position in function of gap beteen snaps (0 ,1 , 2, ...). Sets the scroll position to snapIndex instantly.

// In create function ...
let myCamera = new ScrollingCamera(this);
let cursors = this.input.keyboard.createCursorKeys();
cursors.down.on('down', () => myCamera.moveToSnap(myCamera.snapIndex - 1));
cursors.up.on('down', () => myCamera.moveToSnap(myCamera.snapIndex + 1));

Public properties

Besides inherited properties and the properties declared in the constructor, there are only one public property:

• snapIndex {number}: Stores the snap position in function of gap beteen snaps (0 ,1 , 2, ...). This property is send with the event snap as argument.

License

ScrollingCamera is licensed under the terms of the MIT open source license.