# Apply glitch effect on scroll event by Three.js

## Background

I’ve just started to learn Three.js. As you know this library is powerful to create 3d animation, motion graphics and effects. In this post I’m going to explain how I achieved to implement glitch image by scrolling using React. There is no meaning what I chose React. That is simply one of major framework and it’s a bit helpful for some developers but I don’t mention about React in this article.

## What is Glitch?

Glitch is a word to depict collapsed or bug images. To express those of images there are various methodologies such as scratching, distorting, noise and jaggy.

I initially thought that RGB glitch was a cool effect and easy to implement because the glitched image is composed of only 3 images separated with R, B, G channels from original image. Indeed I found an example in learning-threejs repository including the shader file.

https://github.com/josdirksen/learning-threejs

#### Setup

First of all I created THEE.Mesh objects to display images then added material with shader.

// NOTE: Setup material
const material = originalMaterial.clone();
material.uniforms.tDiffuse.value = cardTexture;

cardTexture is a THREE.Texture loaded from THREE.TextureLoader. This texture is assigned to tDiffuse property that is used in shader as image data. I placed these mesh objects along DIV layout in DOM tree into canvas. The layout is inspired by this sample and borrowed images in the repository.

## Let’s glitching

Thanks to this fantastic example all I need to do is change distance among RGB images and direction on scroll event. I customised this properties when scroll up event occurred, 90 degrees shifts with particular RGB amount value like this. Every time the content of the page is scrolled, this RGB glitch effect is applied.

let offset = 1.2
const scrollTop = Math.max(window.pageYOffset, document.documentElement.scrollTop, document.body.scrollTop)
const currentScrollY = scrollTop
const isDownScroll = oldScrollY >= currentScrollY
let diff = Math.floor((oldScrollY - currentScrollY)) * offset
let direction = 90

if (isDownScroll) {
diff *= -1
direction *= -1
}
})
const applyRgbShader = (value, direction = 90) => {
planeGeometries.map(card => {
const material = card.material;
material.uniforms.amount.value = value / 300.0;
material.uniforms.angle.value = direction * ( Math.PI / 180 );
});
}

The planeGeometries in applyRgbShader function keeps exactly the targets of THREE.Mesh on canvas. Each item has a texture by an image as a material that I’ve initialised above a couple of code.

## Conclusion

Applying glitch effect to a specific object is not difficult to apply. But if you want to apply it throughout page or container, you may have to dive into more complicate three.js world. I also explains how to apply shader throughout a container. You can see the sample at above gif image on resize.

You can see the final image in this post to visit my portfolio site.

https://mitsuyacider.com/

I put this glitch scroll sample code in Github. I hope this post is helpful for some developers.

https://github.com/mitsuyacider/GlitchScroll