Tracing Beam

A Beam that follows the path of an SVG as the user scrolls. Adjusts beam length with scroll speed.

Svelte

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Changelog

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In dolore veniam excepteur eu est et sunt velit. Ipsum sint esse veniam fugiat esse qui sint ad sunt reprehenderit do qui proident reprehenderit. Laborum exercitation aliqua reprehenderit ea sint cillum ut mollit.

Launch Week

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Installation

Install Dependencies

npm i svelte-motion clsx tailwind-merge

Add util file

src/lib/utils/cn.ts 
import { type ClassValue, clsx } from 'clsx';
import { twMerge } from 'tailwind-merge';
        
export function cn(...inputs: ClassValue[]) {
    return twMerge(clsx(inputs));
}

Add the following code in tailwind.config.ts file

tailwind.config.ts 
import flattenColorPalette from 'tailwindcss/lib/util/flattenColorPalette';

const config = {
	// ... other properties
	plugins: [
		// ...other plugins
		addVariablesForColors
	]
};

// This plugin adds each Tailwind color as a global CSS variable, e.g. var(--gray-200).
function addVariablesForColors({ addBase, theme }: any) {
	let allColors = flattenColorPalette(theme('colors'));
	let newVars = Object.fromEntries(
		Object.entries(allColors).map(([key, val]) => [`--${key}`, val])
	);

	addBase({
		':root': newVars
	});
}

Copy the source code

src/lib/components/ui/TracingBeam/TracingBeam.svelte 
<script lang="ts">
	import { onMount } from 'svelte';
	import { tweened } from 'svelte/motion';
	import { cubicOut } from 'svelte/easing';

	let svgHeight = 0;
	let velo = 0;
	let y1 = tweened(50, { duration: 500, easing: cubicOut });
	let y2 = tweened(50, { duration: 500, easing: cubicOut });
	let scrollYProgress = 0;
	let scrollYProgressVelocity = 0;
	let ref: HTMLDivElement;
	let contentRef: HTMLDivElement;

	onMount(() => {
		if (typeof window !== 'undefined') {
			svgHeight = contentRef.offsetHeight;
			window.addEventListener('scroll', handleScroll);
		}
		return () => {
			if (typeof window !== 'undefined') {
				window.removeEventListener('scroll', handleScroll);
			}
		};
	});

	$: {
		if (typeof window !== 'undefined') {
			scrollYProgress = window.scrollY / document.body.offsetHeight;
			scrollYProgressVelocity = scrollYProgress - scrollYProgressVelocity;
			velo = scrollYProgressVelocity;
			y1.set(scrollYProgress * (svgHeight - velo * 500));
			y2.set(scrollYProgress * (svgHeight - velo * 2000));
		}
	}

	let ticking = false;
	function handleScroll() {
		if (!ticking) {
			if (typeof window !== 'undefined') {
				window.requestAnimationFrame(() => {
					scrollYProgress = window.scrollY / document.body.offsetHeight;
					ticking = false;
				});
				ticking = true;
			}
		}
	}
</script>

<div bind:this={ref} class="relative mx-auto h-full w-full max-w-4xl">
	<div class="absolute -left-20 top-3">
		<div
			class="border-netural-200 ml-[27px] flex h-4 w-4 items-center justify-center rounded-full border shadow-sm"
			style="box-shadow: {scrollYProgress > 0 ? 'none' : 'rgba(0, 0, 0, 0.24) 0px 3px 8px'}"
		>
			<div
				class="h-2 w-2 rounded-full border border-neutral-300 bg-white"
				style="background-color: {scrollYProgress > 0
					? 'white'
					: 'var(--emerald-500)'}; border-color: {scrollYProgress > 0
					? 'white'
					: 'var(--emerald-600)'}"
			/>
		</div>
		<svg
			viewBox={`0 0 20 ${svgHeight}`}
			width="20"
			height={svgHeight}
			class=" ml-4 hidden lg:block"
			aria-hidden="true"
		>
			<path
				d={`M 1 0V -36 l 18 24 V ${svgHeight * 0.8} l -18 24V ${svgHeight}`}
				fill="none"
				stroke="#9091A0"
				stroke-opacity="0.16"
			/>
			<path
				d={`M 1 0V -36 l 18 24 V ${svgHeight * 0.8} l -18 24V ${svgHeight}`}
				fill="none"
				stroke="url(#gradient)"
				stroke-width="4"
				class="motion-reduce:hidden"
			/>
			<defs>
				<linearGradient
					id="gradient"
					gradientUnits="userSpaceOnUse"
					x1="0"
					x2="0"
					y1={$y1}
					y2={$y2}
				>
					<stop stop-color="#18CCFC" stop-opacity="0"></stop>
					<stop stop-color="#18CCFC"></stop>
					<stop offset="0.325" stop-color="#6344F5"></stop>
					<stop offset="1" stop-color="#AE48FF" stop-opacity="0"></stop>
				</linearGradient>
			</defs>
		</svg>
	</div>
	<div bind:this={contentRef}>
		<slot />
	</div>
</div>
src/lib/components/ui/TracingBeam/index.ts 
import TracingBeam from './TracingBeam.svelte';

export { TracingBeam };

Props

TracingBeam
Prop Type Description
className string | undefined The class name of the child component.