check2d

+ @

check2d is a feature-complete 2D collision detection library for JavaScript, designed for real-time games and simulations.

It combines a Bounding Volume Hierarchy (BVH) broad phase with Separating Axis Theorem (SAT) narrow phase detection, providing fast and accurate collision checks across many shape types.

$3

- BVH-based broad phase for high performance
- SAT-based precise collision detection
- supports boxes, circles, ellipses, polygons, lines, points
- raycasting, offsets, rotation, scaling
- group-based collision filtering
- visual debugging helpers
- browser and Node.js support
- battle-tested and well benchmarked

---

demos

- Stress test
https://nenjack.github.io/check2d/demo/?stress
- Tank demo
https://nenjack.github.io/check2d/demo/
- StackBlitz
https://stackblitz.com/edit/check2d
- CodePan
https://nenjack.github.io/codepan/#/boilerplate/check2d?pans=console,html

---

quick start

``ts
const { System } = require('check2d')

const system = new System()
``

$3

`ts
const { Box, Circle, Polygon } = require('check2d')

const box = system.createBox({ x: 0, y: 0 }, 10, 10)
const circle = new Circle({ x: 5, y: 0 }, 5)

system.insert(circle)
`

---

body manipulation

Bodies can be transformed freely. Changes are batched and applied once.

`ts
box.setPosition(10, 5, false)
box.setAngle(Math.PI / 4, false)
box.setScale(2, 1, false)
box.move(1, false)

box.updateBody()
`

Supported features include:

* position, rotation, scale
* movement in facing direction
* offsets relative to body center
* AABB access
* padding to reduce BVH reinserts
* group-based collision filtering

---

collision checks

`ts
system.checkAll((result) => {
console.log(result)
})

system.checkOne(box, (result) => {
console.log(result)
})

// optional automatic separation
system.separate()
`

$3

`ts
const points = system.getCollisionPoints(result.a, result.b)
`

---

raycasting

`ts
const hit = system.raycast(
{ x: 0, y: 0 },
{ x: 0, y: -10 },
(body) => true
)

if (hit) {
const { point, body } = hit
console.log(point, body)
}
`

---

visual debugging

Draw bodies directly to a context:

`ts
context.beginPath()
system.draw(context)
context.stroke()
`

Draw BVH bounding boxes:

`ts
context.beginPath()
system.drawBVH(context)
context.stroke()
`

---

browser usage

`js
import { System } from 'https://esm.sh/check2d'
`

---

testing & benchmark

`bash
Test Suites: 12 passed, 12 total
Tests: 84 passed, 84 total
`

Run benchmarks and stress tests:

`bash
git clone https://github.com/nenjack/check2d.git
cd check2d
npm i
npm run benchmark
`

---

installation

`bash
yarn add check2d
`

---

documentation

API reference and guides:
https://nenjack.github.io/check2d/

---

why not a physics engine?

Physics engines like Matter.js or Planck.js are excellent when full simulation is required, but they often introduce unnecessary overhead when only collision detection is needed.

check2d focuses purely on collision detection:

* no gravity
* no forces
* no assumptions about movement

This makes it ideal as a standalone collision system or as the foundation of a custom physics engine.

---

contributing

Contributions are welcome.

* run npm run precommit
* follow conventional commits
* avoid using any`

---

license

MIT