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.

highlights

• 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

const { System } = require('check2d')

const system = new System()
Copy

creating bodies

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)
Copy

---

body manipulation

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

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

box.updateBody()
Copy

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

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

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

// optional automatic separation
system.separate()
Copy

collision points

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

---

raycasting

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

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

---

visual debugging

Draw bodies directly to a <canvas> context:

context.beginPath()
system.draw(context)
context.stroke()
Copy

Draw BVH bounding boxes:

context.beginPath()
system.drawBVH(context)
context.stroke()
Copy

---

browser usage

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

---

testing & benchmark

Test Suites: 12 passed, 12 total
Tests:       84 passed, 84 total
Copy

Run benchmarks and stress tests:

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

---

installation

yarn add check2d
Copy

---

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