Today we’d like to share an interesting distortion effect with you. The main concept of this demo is to use a displacement map in order to distort an underlying image, giving it different types of effects. To demonstrate the liquid-like transitions between images, we’ve created a slideshow.

What a displacement map generally does, is using an image as a texture, that is later applied to an object, giving the illusion that the underlying object is wrapped around that texture. This is a technique commonly used in many different areas, but today we’ll explore how this can be applied to a simple image slideshow.

We’ll be using PixiJS as our renderer and filtering engine and GSAP for our animations.

Getting Started

In order to have a displacement effect, you need a displacement map texture. In this demo’s code we’ve provided with different types of textures you can use, but of course you can create one of your own, for example by using Photoshop’s render tool. Keep in mind that this image’s dimensions affect the end result, so playing around with differently sized textures, might give you different effect looks.

A general rule of thumb is that your texture image should be a power of 2 sized texture. What this means is that its width and height can be doubled-up or divided-down by 2. This ensures that your texture is optimized to run fast, without consuming too much memory. In other words the suggested dimensions for your texture image (width and/or height), would be: 8, 16, 32, 64, 128, 256, 512, 1024, 2048 etc.

For the demos, we’ve created a slideshow that, when navigating, shows the effect as a transition on the slides. We’ll also add some other options, but we’ll just go through the main idea of the distortion effect.

Markup

Our base markup for this demo is really minimal. We just need the navigation buttons for our slider and a wrapper for the slides. We use this wrapper to pass our slides to our component, therefore we hide it by default with CSS. This markup to JS approach may simplify the task of adding images to the slideshow, when working in a more dynamic environment. However, if it suits you better, you could just easily pass them as an array, upon initializing.

<div class="slide-wrapper"> <div class="slide-item"> <h3 class="slide-item__title">Slide 1</h3> <img src="..." class="slide-item__image"> </div> <div class="slide-item"> <h3 class="slide-item__title">Slide 2</h3> <img src="..." class="slide-item__image"> </div> <div class="slide-item"> <h3 class="slide-item__title">Slide 3</h3> <img src="..." class="slide-item__image"> </div> </div> <a href="#" class="scene-nav scene-nav--prev" data-nav="previous">PREV</a> <a href="#" class="scene-nav scene-nav--next" data-nav="next">NEXT</a>

CSS

In our CSS we hide our wrapper and position the navigation buttons at the left and right edges of the viewport.

.slide-wrapper { display: none; } .scene-nav { position: fixed; top: 50%; transform: translateY(-50%); z-index: 10; display: inline-block; } .scene-nav--next { right: 2%; } .scene-nav--prev { left: 2%; }

Setting up the stage

The idea is fairly simple: we add all of our slides into a container, apply the displacement filter and render. Then, when clicking the navigation buttons, we set the alpha property of the current image to 0, set the next one’s to 1 and tweak the displacement filter while navigating.

var renderer = new PIXI.autoDetectRenderer(); var stage = new PIXI.Container(); var slidesContainer = new PIXI.Container(); var displacementSprite = new PIXI.Sprite.fromImage( displacementImage ); var displacementFilter = new PIXI.filters.DisplacementFilter( displacementSprite ); // Add canvas to the HTML document.body.appendChild( renderer.view ); // Add child container to the stage stage.addChild( slidesContainer ); // Set the filter to stage stage.filters = [displacementFilter]; // We load the sprites to the slides container and position them at the center of the stage // The sprites array is passed to our component upon its initialization // If our slide has text, we add it as a child to the image and center it function loadPixiSprites( sprites ) { for ( var i = 0; i < sprites.length; i++ ) { var texture = new PIXI.Texture.fromImage( sprites[i] ); var image = new PIXI.Sprite( texture ); if ( texts ) { // Base styles for our Text var textStyle = new PIXI.TextStyle({ fill: '#ffffff', wordWrap: true, wordWrapWidth: 400 }); var text = new PIXI.Text( texts[i], textStyle); image.addChild( text ); // Center each to text to the image text.anchor.set(0.5); text.x = image.width / 2; text.y = image.height / 2; } image.anchor.set(0.5); image.x = renderer.width / 2; image.y = renderer.height / 2; slidesContainer.addChild( image ); } };

That would be the most basic setup you’d need in order for the scene to be ready. Next thing we want to do is handle the clicks of the navigation buttons. Like we said, when the user clicks on the next or previous button, we change the alpha property of the according slide and tweak our Displacement Filter. We use a simple timeline for this, which you could of course customize accordingly.

// We listen at each navigation element click and call the move slider function // passing it the index we want to go to var currentIndex = 0; var slideImages = slidesContainer.children; var isPlaying = false; for ( var i = 0; i < nav.length; i++ ) { var navItem = nav[i]; navItem.onclick = function( event ) { // Make sure the previous transition has ended if ( isPlaying ) { return false; } if ( this.getAttribute('data-nav') === 'next' ) { if ( that.currentIndex >= 0 && that.currentIndex < slideImages.length - 1 ) { moveSlider( currentIndex + 1 ); } else { moveSlider( 0 ); } } else { if ( that.currentIndex > 0 && that.currentIndex < slideImages.length ) { moveSlider( currentIndex - 1 ); } else { moveSlider( spriteImages.length - 1 ); } } return false; } } // Our transition between the slides // On our timeline we set the alpha property of the relevant slide to 0 or 1 // and scale out filter on the x & y axis accordingly function moveSlider( newIndex ) { isPlaying = true; var baseTimeline = new TimelineMax( { onComplete: function () { that.currentIndex = newIndex; isPlaying = false; }}); baseTimeline .to(displacementFilter.scale, 1, { x: 200, y: 200 }) .to(slideImages[that.currentIndex], 0.5, { alpha: 0 }) .to(slideImages[newIndex], 0.5, { alpha: 1 }) .to(displacementFilter.scale, 1, { x: 20, y: 20 } ); };

Finally, we have to render our scene and optionally add some default animations.

// Use Pixi's Ticker class to render our scene // similar to requestAnimationFrame var ticker = new PIXI.ticker.Ticker(); ticker.add( function( delta ) { // Optionally have a default animation displacementSprite.x += 10 * delta; displacementSprite.y += 3 * delta; // Render our stage renderer.render( stage ); });

Working Demo

This should sum up the most basic parts of how the demo works and give you a good starting point if you want to edit it according to your needs. However, if you don’t want to mess with too much code and need a quick working demo to play on your own, there are several options you could use when you initialize the component. So just include the script on your page and add the following code wherever you want to show your slideshow. Play around with different values to get started and don’t forget to try out different displacement map textures for different effects.

// Select all your images var spriteImages = document.querySelectorAll( '.slide-item__image' ); var spriteImagesSrc = []; var texts = []; for ( var i = 0; i < spriteImages.length; i++ ) { var img = spriteImages[i]; // Set the texts you want to display to each slide // in a sibling element of your image and edit accordingly if ( img.nextElementSibling ) { texts.push(img.nextElementSibling.innerHTML); } else { texts.push(''); } spriteImagesSrc.push( img.getAttribute('src' ) ); } // Initialise the Slideshow var initCanvasSlideshow = new CanvasSlideshow({ // pass the images you want as an array sprites: spriteImagesSrc, // if you want your slides to have title texts, pass them as an array texts: texts, // set your displacement texture displacementImage: 'https://imgur.com/a/Ea3wo', // optionally start with a default animation autoPlay: true, // [x, y] controls the speed for your default animation autoPlaySpeed: [10, 3], // [x, y] controls the effect amount during transitions displaceScale: [200, 70], // choose whether or not you slideshow will take up all the space of the viewport fullScreen: true, // If you choose to not have a fullscreen slideshow, set the stage's width & height accordingly stageWidth: 800, stageHeight: 600, // add you navigation element. Should have a 'data-nav' attribute with a value of next/previous navElement: document.querySelectorAll( '.scene-nav' ), // will fit the filter bounding box to the renderer displaceAutoFit: false });

Interactive

Last thing we want to do is optionally make our stage interactive. That is instead of auto playing, have our effect interact with our mouse. Just set the the interactive property to be true and play around with your mouse.

var initCanvasSlideshow = new CanvasSlideshow({ interactive: true ... });

In all mouse interactions we listen for the corresponding event, and based on the event data, we scale our displacement event respectively. It looks like this:

// Set our container to interactive mode slidesContainer.interactive = true; slidesContainer.buttonMode = true; // Our animation var rafID, mouseX, mouseY; function rotateSpite() { displacementSprite.rotation += 0.001; rafID = requestAnimationFrame( rotateSpite ); } slidesContainer.pointerover = function( mouseData ){ mouseX = mouseData.data.global.x; mouseY = mouseData.data.global.y; TweenMax.to( displacementFilter.scale, 1, { x: "+=" + Math.sin( mouseX ) * 100 + "", y: "+=" + Math.cos( mouseY ) * 100 + "" }); rotateSpite(); } slidesContainer.pointerdown = function( mouseData ){ mouseX = mouseData.data.global.x; mouseY = mouseData.data.global.y; TweenMax.to( displacementFilter.scale, 1, { x: "+=" + Math.sin( mouseX ) * 1200 + "", y: "+=" + Math.cos( mouseY ) * 200 + "" }); } slidesContainer.pointerout = function( mouseData ){ TweenMax.to( displacementFilter.scale, 1, { x: 0, y: 0 }); cancelAnimationFrame( rafID ); } slidesContainer.pointerup = function( mouseData ){ TweenMax.to( displacementFilter.scale, 1, { x: 0, y: 0 }); cancelAnimationFrame( rafID ); }

Simple as that! Hope this demo gives you a good starting point to play around with different filters and make it easy for you to create your own.