Creating an Infinite Auto-Scrolling Gallery using WebGL with OGL and GLSL Shaders

Hello everyone, introducing myself a little bit first, I’m Luis Henrique Bizarro, I’m a Senior Creative Developer at Active Theory based in São Paulo, Brazil. It’s always a pleasure to me having the opportunity to collaborate with Codrops to help other developers learn new things, so I hope everyone enjoys this tutorial!

In this tutorial I’ll explain you how to create an auto scrolling infinite image gallery. The image grid is also scrollable be user interaction, making it an interesting design element to showcase works. It’s based on this great animation seen on made by Jesper Landberg.

I’ve been using the technique of styling images first with HTML + CSS and then creating an abstraction of these elements inside WebGL using some camera and viewport calculations in multiple websites, so this is the approach we’re going to use in this tutorial.

The good thing about this implementation is that it can be reused across any WebGL library, so if you’re more familiar with Three.js or Babylon.js than OGL, you’ll also be able to achieve the same results using a similar code, when it’s about shading and scaling the plane meshes.

So let’s get into it!

Implementing our HTML markup

The first step is implementing our HTML markup. We’re going to use <figure> and <img> elements, nothing special here, just the standard:

<div class="demo-1__gallery"> <figure class="demo-1__gallery__figure"> <img class="demo-1__gallery__image" src="images/demo-1/1.jpg"> </figure> <!-- Repeating the same markup until 12.jpg. -->

Setting our CSS styles

The second step is styling our elements using CSS. One of the first things I do in a website is defining the font-size of the html element because I use rem to help with the responsive breakpoints.

This comes in handy if you’re doing creative websites that only require two or three different breakpoints, so I highly recommend starting using it if you haven’t adopted rem yet.

One thing I’m also using is calc() with the size of the designs. In our tutorial we’re going to use 1920 as our main width, scaling our font-size depending on the screen size of 100vw. This results in 10px at a 1920px screen, for example:

html { font-size: calc(100vw / 1920 * 10);

Now let’s style our grid of images. We want to freely place our images across the screen using absolute positioning, so we’re just going to set the height, width and left/top styles across all our demo-1 classes:

.demo-1__gallery { height: 295rem; position: relative; visibility: hidden;
} .demo-1__gallery__figure { position: absolute; &:nth-child(1) { height: 40rem; width: 70rem; } &:nth-child(2) { height: 50rem; left: 85rem; top: 30rem; width: 40rem; } &:nth-child(3) { height: 50rem; left: 15rem; top: 60rem; width: 60rem; } &:nth-child(4) { height: 30rem; right: 0; top: 10rem; width: 50rem; } &:nth-child(5) { height: 60rem; right: 15rem; top: 55rem; width: 40rem; } &:nth-child(6) { height: 75rem; left: 5rem; top: 120rem; width: 57.5rem; } &:nth-child(7) { height: 70rem; right: 0; top: 130rem; width: 50rem; } &:nth-child(8) { height: 50rem; left: 85rem; top: 95rem; width: 40rem; } &:nth-child(9) { height: 65rem; left: 75rem; top: 155rem; width: 50rem; } &:nth-child(10) { height: 43rem; right: 0; top: 215rem; width: 30rem; } &:nth-child(11) { height: 50rem; left: 70rem; top: 235rem; width: 80rem; } &:nth-child(12) { left: 0; top: 210rem; height: 70rem; width: 50rem; }
} .demo-1__gallery__image { height: 100%; left: 0; object-fit: cover; position: absolute; top: 0; width: 100%;

Note that we’re hiding the visibility of our HTML, because it’s not going to be visible for the users since we’re going to load these images inside the <canvas> element. But below you can find a screenshot of what the result will look like.

Creating our OGL 3D environment

Now it’s time to get started with the WebGL implementation using OGL. First let’s create an App class that is going to be the entry point of our demo and inside of it, let’s also create the initial methods: createRenderer, createCamera, createScene, onResize and our requestAnimationFrame loop with update.

import { Renderer, Camera, Transform } from 'ogl' class App { constructor () { this.createRenderer() this.createCamera() this.createScene() this.onResize() this.update() this.addEventListeners() } createRenderer () { this.renderer = new Renderer({ alpha: true }) = document.body.appendChild( } createCamera () { = new Camera( = 45 = 5 } createScene () { this.scene = new Transform() } /** * Wheel. */ onWheel (event) { } /** * Resize. */ onResize () { this.screen = { height: window.innerHeight, width: window.innerWidth } this.renderer.setSize(this.screen.width, this.screen.height){ aspect: / }) const fov = * (Math.PI / 180) const height = 2 * Math.tan(fov / 2) * const width = height * this.viewport = { height, width } } /** * Update. */ update () { this.renderer.render({ scene: this.scene, camera: }) window.requestAnimationFrame(this.update.bind(this)) } /** * Listeners. */ addEventListeners () { window.addEventListener('resize', this.onResize.bind(this)) window.addEventListener('mousewheel', this.onWheel.bind(this)) window.addEventListener('wheel', this.onWheel.bind(this)) }
} new App()

Explaining some part of our App.js file

In our createRenderer method, we’re initializing one renderer with alpha enabled, storing our GL context ( reference in the variable and appending our <canvas> element to our document.body.

In our createCamera method, we’re just creating a new Camera and setting some of its attributes: fov and its z position.

In our createScene method, we’re using the Transform class, that is the representation of a new scene that is going to contain all our planes that represent our images in the WebGL environment.

The onResize method is the most important part of our initial setup. It’s responsible for three different things:

  1. Making sure we’re always resizing the <canvas> element with the correct viewport sizes.
  2. Updating our perspective dividing the width and height of the viewport.
  3. Storing in the variable this.viewport, the value representations that will help to transform pixels into 3D environment sizes by using the fov from the camera.

The approach of using the camera.fov to transform pixels in 3D environment sizes is an approach used very often in multiple WebGL implementations. Basically what it does is making sure that if we do something like: this.mesh.scale.x = this.viewport.width; it’s going to make our mesh fit the entire screen width, behaving like width: 100%, but in 3D space.

And finally in our update, we’re setting our requestAnimationFrame loop and making sure we keep rendering our scene.

Create our reusable geometry instance

It’s a good practice to keep memory usage low by always reusing the same geometry reference no matter what WebGL library you’re using. To represent all our images, we’re going to use a Plane geometry, so let’s create a new method and store this new geometry inside the this.planeGeometry variable.

import { Renderer, Camera, Transform, Plane } from 'ogl' createGeometry () { this.planeGeometry = new Plane(

Select all images and create a new class for each one

Now it’s time to use document.querySelector to select all our images and create one reusable class that is going to represent our images. (We’re going to create a single Media.js file later.)

createMedias () { this.mediasElements = document.querySelectorAll('.demo-1__gallery__figure') this.medias = Array.from(this.mediasElements).map(element => { let media = new Media({ element, geometry: this.planeGeometry, gl:, scene: this.scene, screen: this.screen, viewport: this.viewport }) return media })

As you can see, we’re just selecting all .demo-1__gallery__figure elements, going through them and generating an array of `this.medias` with new instances of Media.

Now it’s important to start attaching this array in important pieces of our setup code.

Let’s first include all our media inside the method onResize and also call media.onResize for each one of these new instances:

if (this.medias) { this.medias.forEach(media => media.onResize({ screen: this.screen, viewport: this.viewport }))

And inside our update method, we’re going to call media.update() as well:

if (this.medias) { this.medias.forEach(media => media.update())

Setting up our Media.js file and class

Our Media class is going to use Mesh, Program and Texture classes from OGL to create a 3D plane and attribute a texture to it, which in our case is going to be our images.

In our constructor, we’re going to store all variables that we need and that were passed in the new Media() initialization from index.js:

import { Mesh, Program, Texture } from 'ogl' import fragment from 'shaders/fragment.glsl'
import vertex from 'shaders/vertex.glsl' export default class { constructor ({ element, geometry, gl, scene, screen, viewport }) { this.element = element this.image = this.element.querySelector('img') this.geometry = geometry = gl this.scene = scene this.screen = screen this.viewport = viewport this.createMesh() this.createBounds() this.onResize() }

In our createMesh method, we’ll load the image texture using the this.image.src attribute, then create a new Program, which is basically a representation of the material we’re applying to our Mesh. So our method looks like this:

createMesh () { const image = new Image() const texture = new Texture( image.src = this.image.src image.onload = _ => { texture.image = image } const program = new Program(, { fragment, vertex, uniforms: { tMap: { value: texture }, uScreenSizes: { value: [0, 0] }, uImageSizes: { value: [0, 0] } }, transparent: true }) this.plane = new Mesh(, { geometry: this.geometry, program }) this.plane.setParent(this.scene)

Looks pretty simple, right? After we generate a new Mesh, we’re setting the plane as children of this.scene, so we’re including our mesh inside our main scene.

As you’ve probably noticed, our Program receives fragment and vertex. These both represent the shaders we’re going to use on our planes. For now, we’re just using simple implementations of both.

In our vertex.glsl file we’re getting the uv and position attributes, and making sure we’re rendering our planes in the right 3D world position.

attribute vec2 uv;
attribute vec3 position; uniform mat4 modelViewMatrix;
uniform mat4 projectionMatrix; varying vec2 vUv; void main() { vUv = uv; gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);

In our fragment.glsl file, we’re receiving a tMap texture, as you can see in the tMap: { value: texture } declaration, and rendering it in our plane geometry:

precision highp float; uniform sampler2D tMap; varying vec2 vUv; void main() { gl_FragColor.rgb = texture2D(tMap, vUv).rgb; gl_FragColor.a = 1.0;

The createBounds method is important to make sure we’re positioning and scaling our planes in the correct DOM elements positions, so it’s basically going to call for this.element.getBoundingClientRect() to get the right position of our planes, and then after that using these values to calculate the 3D values of our plane.

createBounds () { this.bounds = this.element.getBoundingClientRect() this.updateScale() this.updateX() this.updateY()
} updateScale () { this.plane.scale.x = this.viewport.width * this.bounds.width / this.screen.width this.plane.scale.y = this.viewport.height * this.bounds.height / this.screen.height
} updateX (x = 0) { this.plane.position.x = -(this.viewport.width / 2) + (this.plane.scale.x / 2) + ((this.bounds.left - x) / this.screen.width) * this.viewport.width
} updateY (y = 0) { this.plane.position.y = (this.viewport.height / 2) - (this.plane.scale.y / 2) - (( - y) / this.screen.height) * this.viewport.height
} update (y) { this.updateScale() this.updateX() this.updateY(y)

As you’ve probably noticed, the calculations for scale.x and scale.y are going to stretch our plane to make it the same width and height of the <img> elements. And the position.x and position.y takes the offset from the element and makes our translate our planes to the correct x and y axis in 3D.

And let’s not forget our onResize method, which is basically going to call createBounds again to refresh our getBoundingClientRect values and make sure we keep our 3D implementation responsive as well.

onResize (sizes) { if (sizes) { const { screen, viewport } = sizes if (screen) this.screen = screen if (viewport) this.viewport = viewport } this.createBounds()

This is the result we’ve got so far.

Implement cover behavior in fragment shaders

As you’ve probably noticed, our images are stretched. It happens because we need to make proper calculations in the fragment shaders in order to have a behavior like object-fit: cover; or background-size: cover; in WebGL.

I like to use an approach to pass the images’ real sizes and do some ratio calculations inside the fragment shader, so let’s adapt our code to this approach. So in our Program, we’re going to pass two new uniforms called uPlaneSizes and uImageSizes:

const program = new Program(, { fragment, vertex, uniforms: { tMap: { value: texture }, uPlaneSizes: { value: [0, 0] }, uImageSizes: { value: [0, 0] } }, transparent: true

Now we need to update our fragment.glsl and use these values to calculate our images ratios:

precision highp float; uniform vec2 uImageSizes;
uniform vec2 uPlaneSizes;
uniform sampler2D tMap; varying vec2 vUv; void main() { vec2 ratio = vec2( min((uPlaneSizes.x / uPlaneSizes.y) / (uImageSizes.x / uImageSizes.y), 1.0), min((uPlaneSizes.y / uPlaneSizes.x) / (uImageSizes.y / uImageSizes.x), 1.0) ); vec2 uv = vec2( vUv.x * ratio.x + (1.0 - ratio.x) * 0.5, vUv.y * ratio.y + (1.0 - ratio.y) * 0.5 ); gl_FragColor.rgb = texture2D(tMap, uv).rgb; gl_FragColor.a = 1.0;

And then we also need update our image.onload method to pass naturalWidth and naturalHeight to uImageSizes:

image.onload = _ => { program.uniforms.uImageSizes.value = [image.naturalWidth, image.naturalHeight] texture.image = image

And createBounds to update the uPlaneSizes uniforms:

createBounds () { this.bounds = this.element.getBoundingClientRect() this.updateScale() this.updateX() this.updateY() this.plane.program.uniforms.uPlaneSizes.value = [this.plane.scale.x, this.plane.scale.y]

That’s it! Now we have properly scaled images.

Implementing smooth scrolling

Before we implement our infinite logic, it’s good to start making scrolling work properly. In our setup code, we have included a onWheel method, which is going to be used to lerp some variables and make our scroll butter smooth.

In our constructor from index.js, let’s create the this.scroll object with these variables:

this.scroll = { ease: 0.05, current: 0, target: 0,

Now let’s update our onWheel implementation. When working with wheel events, it’s always important to normalize it, because it behaves differently based on the browser, I’ve been using normalize-wheel library to help on it:

import NormalizeWheel from 'normalize-wheel' onWheel (event) { const normalized = NormalizeWheel(event) const speed = normalized.pixelY += speed * 0.5

Let’s also create our lerp utility function inside the file utils/math.js:

export function lerp (p1, p2, t) { return p1 + (p2 - p1) * t

And now we just need to lerp from the this.scroll.current to the inside the update method. And finally pass it to the media.update() methods:

update () { this.scroll.current = lerp(this.scroll.current,, this.scroll.ease) if (this.medias) { this.medias.forEach(media => media.update(this.scroll.current)) }

After that we already have a result like this.

Making our smooth scrolling infinite

The approach of making an infinite scrolling logic is basically repeating the same grid over and over while the user keeps scrolling your page. Since the user can scroll up or down, you also need to take under consideration what direction is being scrolled, so overall the algorithm should work this way:

  • If you’re scrolling down, your elements move up — when your first element isn’t on the screen anymore, you should move it to the end of the list.
  • If you’re scrolling up, your elements move to down — when your last element isn’t on the screen anymore, you should move it to the start of the list.

To explain it in a visual way, let’s say we’re scrolling down and the red area is our viewport and the blue elements are not in the viewport anymore.

When we are in this state, we just need to move the blue elements to the end of our gallery grid, which is the entire height of our gallery: 295rem.

Let’s include the logic for it then. First, we need to create a new variable called this.scroll.last to store the last value of our scroll, this is going to be checked to give us up or down strings:

this.scroll = { ease: 0.05, current: 0, target: 0, last: 0

In our update method, we need to include the following lines of validations and pass this.direction to our this.medias elements.

update () { this.scroll.current = lerp(this.scroll.current,, this.scroll.ease) if (this.scroll.current > this.scroll.last) { this.direction = 'down' } else if (this.scroll.current < this.scroll.last) { this.direction = 'up' } if (this.medias) { this.medias.forEach(media => media.update(this.scroll.current, this.direction)) } this.renderer.render({ scene: this.scene, camera: }) this.scroll.last = this.scroll.current window.requestAnimationFrame(this.update.bind(this))

Then we need to get the total gallery height and transform it to 3D dimensions, so let’s include a querySelector of .demo-1__gallery and call the createGallery method in our index.js constructor.

createGallery () { = document.querySelector('.demo-1__gallery')

It’s time to do the real calculations using this selector, so in our onResize method, we need to include the following lines:

this.galleryBounds =
this.galleryHeight = this.viewport.height * this.galleryBounds.height / this.screen.height

The this.galleryHeight variable now is storing the 3D size of the entire grid, now we need to pass it to both onResize and new Media() calls:

if (this.medias) { this.medias.forEach(media => media.onResize({ height: this.galleryHeight, screen: this.screen, viewport: this.viewport }))
this.medias = Array.from(this.mediasElements).map(element => { let media = new Media({ element, geometry: this.planeGeometry, gl:, height: this.galleryHeight, scene: this.scene, screen: this.screen, viewport: this.viewport }) return media

And then inside our Media class, we need to store the height as well in the constructor and also in the onResize methods:

constructor ({ element, geometry, gl, height, scene, screen, viewport }) { this.height = height
onResize (sizes) { if (sizes) { const { height, screen, viewport } = sizes if (height) this.height = height if (screen) this.screen = screen if (viewport) this.viewport = viewport }

Now we’re going to include the logic to move our elements based on their viewport position, just like our visual representation of the red and blue rectangles.

If the idea is to keep summing up a value based on the scroll and element position, we can achieve this by just creating a new variable called this.extra = 0, this is going to store how much we need to sum (or subtract) of our media, so in our constructor let’s include it:

constructor ({ element, geometry, gl, height, scene, screen, viewport }) { this.extra = 0

And let’s reset it on resizing the browser, to make all values consistent so it doesn’t break when users resizes their viewport:

onResize (sizes) { this.extra = 0

And in our updateY method, we’re going to include it as well:

updateY (y = 0) { this.plane.position.y = ((this.viewport.height / 2) - (this.plane.scale.y / 2) - (( - y) / this.screen.height) * this.viewport.height) - this.extra

Finally, the only thing left now is updating the this.extra variable inside our update method, making sure we’re adding or subtracting the this.height depending on the direction.

const planeOffset = this.plane.scale.y / 2
const viewportOffset = this.viewport.height / 2 this.isBefore = this.plane.position.y + planeOffset < -viewportOffset
this.isAfter = this.plane.position.y - planeOffset > viewportOffset if (direction === 'up' && this.isBefore) { this.extra -= this.height this.isBefore = false this.isAfter = false
} if (direction === 'down' && this.isAfter) { this.extra += this.height this.isBefore = false this.isAfter = false

Since we’re working in 3D space, we’re dealing with cartesian coordinates, that’s why you can notice we’re dividing most things by two (ex: this.viewport.heighht / 2). So that’s also the reason why we had to do a different logic for the this.isBefore and this.isAfter checks.

Awesome, we’re almost finishing our demo! That’s how it looks now, pretty cool to have it endless right?

Including touch events

Let’s also include touch events, so this demo can be more responsive to user interactions! In our addEventListeners method, let’s include some window.addEventListener calls:

window.addEventListener('mousedown', this.onTouchDown.bind(this))
window.addEventListener('mousemove', this.onTouchMove.bind(this))
window.addEventListener('mouseup', this.onTouchUp.bind(this)) window.addEventListener('touchstart', this.onTouchDown.bind(this))
window.addEventListener('touchmove', this.onTouchMove.bind(this))
window.addEventListener('touchend', this.onTouchUp.bind(this))

Then we just need to implement simple touch events calculations, including the three methods: onTouchDown, onTouchMove and onTouchUp.

onTouchDown (event) { this.isDown = true this.scroll.position = this.scroll.current this.start = event.touches ? event.touches[0].clientY : event.clientY
} onTouchMove (event) { if (!this.isDown) return const y = event.touches ? event.touches[0].clientY : event.clientY const distance = (this.start - y) * 2 = this.scroll.position + distance
} onTouchUp (event) { this.isDown = false

Done! Now we also have touch events support enabled for our gallery.

Implementing direction-aware auto scrolling

Let’s also implement auto scrolling to make our interaction even better. In order to achieve that we just need to create a new variable that will store our speed based on the direction the user is scrolling.

So let’s create a variable called this.speed in our index.js file:

constructor () { this.speed = 2

This variable is going to be changed by our down and up validations we have in our update loop, so if the user is scrolling down, we’re going to keep the speed as 2, if the user is scrolling up, we’re going to replace it with -2, and before that we will sum this.speed to the variable:

update () { += this.speed this.scroll.current = lerp(this.scroll.current,, this.scroll.ease) if (this.scroll.current > this.scroll.last) { this.direction = 'down' this.speed = 2 } else if (this.scroll.current < this.scroll.last) { this.direction = 'up' this.speed = -2 }

Implementing distortion shaders

Now let’s make everything even more interesting, it’s time to play a little bit with shaders and distort our planes while the user is scrolling through our page.

First, let’s update our update method from index.js, making sure we expose both current and last scroll values to all our medias, we’re going to do a simple calculation with them.

update () { if (this.medias) { this.medias.forEach(media => media.update(this.scroll, this.direction)) }

And now let’s create two uniforms for our Program shader: uOffset and uViewportSizes, and pass them:

const program = new Program(, { fragment, vertex, uniforms: { tMap: { value: texture }, uPlaneSizes: { value: [0, 0] }, uImageSizes: { value: [0, 0] }, uViewportSizes: { value: [this.viewport.width, this.viewport.height] }, uStrength: { value: 0 } }, transparent: true

As you can probably notice, we’re going to need to set uViewportSizes in our onResize method as well, since this.viewport changes when we resize, so to keep this.viewport.width and this.viewport.height up to date, we also need to include the following lines of code in onResize:

onResize (sizes) { if (sizes) { const { height, screen, viewport } = sizes if (height) this.height = height if (screen) this.screen = screen if (viewport) { this.viewport = viewport this.plane.program.uniforms.uOffset.value = [this.viewport.width, this.viewport.height] } }

Remember the this.scroll update we’ve made from index.js? Now it’s time to include a small trick to generate a speed value inside our Media.js:

update (y, direction) { this.updateY(y.current) this.plane.program.uniforms.uStrength.value = ((y.current - y.last) / this.screen.width) * 10

We’re basically checking the difference between the current and last values, which returns us some kind of “speed” of the scrolling, and dividing it by the this.screen.width, to keep our effect value behaving correctly independently of the width of our screen.

Finally now it’s time to play a little bit with our vertex shader. We’re going to bend our planes a little bit while the user is scrolling through the page. So let’s update our vertex.glsl file with this new code:

#define PI 3.1415926535897932384626433832795 precision highp float;
precision highp int; attribute vec3 position;
attribute vec2 uv; uniform mat4 modelViewMatrix;
uniform mat4 projectionMatrix; uniform float uStrength;
uniform vec2 uViewportSizes; varying vec2 vUv; void main() { vec4 newPosition = modelViewMatrix * vec4(position, 1.0); newPosition.z += sin(newPosition.y / uViewportSizes.y * PI + PI / 2.0) * -uStrength; vUv = uv; gl_Position = projectionMatrix * newPosition;

That’s it! Now we’re also bending our images creating an unique type of effect!

Explaining a little bit of the shader logic: basically what’s implemented in the newPosition.z line is taking into consideration the uViewportSize.y, which is our height from the viewport and the current position.y of our plane, getting the division of both and multiplying by PI that we defined on the very top of our shader file. And then we use the uStrength which is the strength of the bending, that is tight with our scrolling values, making it bend based on how faster you scroll the demo.

That’s the final result of our demo! I hope this tutorial was useful to you and don’t forget to comment if you have any questions!

Photography used in the demos by Planete Elevene and Jayson Hinrichsen.

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