Lightning 3 Renderer (Beta)

Warning: This is beta software and all of the exposed APIs are subject to breaking changes

A powerful 2D scene renderer designed for rendering highly performant user interfaces on web browsers running on embedded devices using WebGL.

The Renderer is not designed for direct application development but instead to provide a lightweight API for front-end application frameworks like Bolt and Solid.

Setup & Commands

# Install renderer + example dependencies
pnpm install

# Build Renderer
pnpm build

# Build Renderer (watch mode)
pnpm watch

# Run unit tests
pnpm test

# Run Visual Regression Tests
pnpm test:visual

# Build API Documentation (builds into ./typedocs folder)
pnpm typedoc

# Launch Example Tests in dev mode (includes Build Renderer (watch mode))
pnpm start

# Launch Example Tests in production mode
# IMPORTANT: To run test examples on embedded devices that use older browser versions
# you MUST run the examples in this mode.
pnpm start:prod

Browser Targets

The Lightning 3 Renderer's goal is to work with the following browser versions and above:

  • Chrome v38 (Released October 7, 2014)

Any JavaScript language features or browser APIs that cannot be automatically transpiled or polyfilled by industry standard transpilers (such as Babel) to target these versions must be carefully considered before use.

Example Tests

The Example Tests sub-project define a set of tests for various Renderer features. This is NOT an automated test. The command below will launch a web server which can be accessed by a web browser for manual testing. However, many of the Example Tests define Snapshots for the Visual Regression Test Runner (see below).

The Example Tests can be launched with:

pnpm start

See examples/README.md for more info.

Visual Regression Tests

In order to prevent bugs on existing Renderer features when new features or bug fixes are added, the Renderer includes a Visual Regression Test Runner along with a set of certified snapshot files that are checked into the repository.

These tests can be launched with:

pnpm test:visual

The captured Snapshots of these tests are optionally defined in the individual Example Tests.

See visual-regression/README.md for more info.

Manual Regression Tests

See [docs/ManualRegressionTests.md].

Release Procedure


Main Space vs Core Space

The Lightning 3 Renderer runs code in two logically seperate environments: the Main Space and the Core Space.

Users of the Renderer will write most of their code for the Main Space using the Main API. This is code that will always run on the browser's main thread and includes initializing the Renderer, creating/modifying/destroying nodes, controlling animations, etc.

The Core Space is where the actual rendering of each UI frame happens and is mostly meant to be transparent to users of the Renderer. However, the Core Space is where all of the code that must be tightly coupled to the rendering process must be loaded and run. The Core Space is extendible by users by writing Core Extensions via the Core API. This allows for users to develop their own shaders, textures, text renderers, dynamic shader effects, and more. Fonts used in an application must be loaded in this way too. The Core Space exists seperately from the Main Space because it is allowed to execute on the page's main thread OR a Web Worker thread. A Core Driver (see below) is used to bridge the Main Space with the Core Space.

Core Drivers

The Lightning 3 Renderer is designed to be able to use a single thread or multiple web worker threads based on the configuration of a Core Driver.

A Core Driver essentially acts as a bridge between the Main and Core spaces defined above.

The Renderer comes with two Core Drivers: the Main Core Driver for single threaded rendering and the ThreadX Core Driver for multi-threaded rendering.

NOTE: The ThreadX Core Driver is experimental and even when the Renderer graduates from beta may still not be ready for production use.

Main Core Driver

The Main Core Driver renders your application on the web page's main thread.

It can be configured into the Renderer like so:

import { MainCoreDriver, RendererMain } from '@lightningjs/renderer';

const renderer = new RendererMain(
// App Config
'app', // App div ID
new MainCoreDriver(), // Main Render driver

// ...

ThreadX Core Driver

The ThreadX Core Driver renders your application on a seperately spawned Web Worker thread.

It can be configured into the Renderer like so:

import {
} from '@lightningjs/renderer';

// The `@lightningjs/vite-plugin-import-chunk-url` Vite plugin is required for this:
import coreWorkerUrl from './common/CoreWorker.js?importChunkUrl';

const renderer = new RendererMain(
// App Config
'app', // App div ID
new ThreadXCoreDriver({

Core Extensions

To load fonts, and/or other custom code into the Core Space, you must write a Core Extension and pass it via dynamically importable URL to the initialization of the Renderer.

Just like with loading the ThreadX Core Web Worker for the ThreadX, you import your core extension using the @lightningjs/vite-plugin-import-chunk-url plugin so that it's code is bundled and loaded seperately from your main app's bundle.

You can write a Core Extension by extending the CoreExtension class from the Core API like so:

import {
type Stage,
} from '@lightning/renderer/core';

export default class MyCoreExtension extends CoreExtension {
async run(stage: Stage) {
// Load fonts into core
new WebTrFontFace('Ubuntu', {}, '/fonts/Ubuntu-Regular.ttf'),

new SdfTrFontFace(

And then in your application's main entry point you can import it using @lightningjs/vite-plugin-import-chunk-url:

import coreExtensionModuleUrl from './MyCoreExtension.js?importChunkUrl';

// Set up driver, etc.

// Initialize the Renderer
const renderer = new RendererMain(
// Other Renderer Config...
coreExtensionModule: coreExtensionModuleUrl,

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