detect-collisions
v9.24.0
Published
Points, Lines, Boxes, Polygons (also hollow), Ellipses, Circles. RayCasting, offsets, rotation, scaling, bounding box padding, flags for static and ghost/trigger bodies
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16,329
Readme
Detect-Collisions
Introduction
Detect-Collisions 💫 is a lightning-fast ⚡️ TypeScript library built to detect collisions between diverse shapes like Points, Lines, Boxes, Polygons (including concave), Ellipses, and Circles. Utilizing Bounding Volume Hierarchy (BVH) and the Separating Axis Theorem (SAT), it offers rapid and accurate collision detection. The library supports RayCasting, offsets, rotation, scaling, and optimizations for: bounding box, flags for non-moving and ghost/trigger bodies and collision groups filtering - making it an ideal choice for high-speed applications in gaming and simulations.
Demos
Installation
npm i detect-collisions --save
API Documentation
For detailed documentation on the library's API, refer to the following link:
Detect-Collisions API Documentation
Usage
Step 1: Initialize Collision System
Initialize a unique collision system using Detect-Collisions:
const { System } = require("detect-collisions");
const system = new System();
Step 2: Understand Body Attributes
Bodies possess various properties:
- Position: Use
setPosition(x: number, y: number)
for teleport andmove(speed: number)
for moving forward in direction of its angle. - Scale: Use
setScale(x: number, y: number)
for setting andscale: Vector
for getting scale - Rotation: Use
setAngle(radians: number)
for setting andangle: number
for getting anddeg2rad(degrees: number)
to convert to radians. - Offset: Use
setOffset(offset: Vector)
for setting andoffset: Vector
for getting offset from the body center. - AABB Bounding Box: Use
aabb: BBox
for inserted orgetAABBAsBBox(): BBox
for non inserted bodies to get the bounding box. - Padding: Use
padding: number
and set to nonzero value to reduce costly reinserts on attributes' change. - Collision Filtering: Use
group: number
for collision filtering, with a range within 0x0 ~ 0x7fffffff. - Body Options: Read more in BodyOptions documentation
Step 3: Create and Manage Bodies
Create bodies of various types and manage them:
const {
Box,
Circle,
Ellipse,
Line,
Point,
Polygon,
} = require("detect-collisions");
// Example: Create and insert box1 body
const box1 = system.createBox(position, width, height, options);
// Example: Create box2 body
const box2 = new Box(position, width, height, options);
// Example: Insert box2 body
system.insert(box2);
Step 4: Manipulate Bodies
Manipulate body attributes and update the collision system:
// if omitted updateNow is true
const updateNow = false;
// this should be time scaled, 1 for example
const speed = 1;
// teleport
box.setPosition(x, y, updateNow);
box.setScale(scaleX, scaleY, updateNow);
box.setAngle(angle, updateNow);
box.move(speed, updateNow);
box.setOffset({ x, y }, updateNow);
console.log(box.dirty); // true
box.updateBody(); // Update the body once, when all manipulations are done
console.log(box.dirty); // false
box.group = group; // Immediate effect, no body/system update needed
console.log(box.dirty); // false
Step 5: Collision Detection and Resolution
Detect collisions and respond accordingly:
if (system.checkAll(callback)) {
// Do something yourself
}
if (system.checkOne(body, callback)) {
// Do something yourself
}
// Or separate bodies based on isStatic/isTrigger
system.separate();
Step 6: Cleaning Up
Remove bodies when they're no longer needed:
system.remove(body);
And that's it! You're now ready to utilize the Detect-Collisions library in your project.
Visual Debugging with Rendering
To facilitate debugging, Detect-Collisions allows you to visually represent the collision bodies. By invoking the draw()
method and supplying a 2D context of a <canvas>
element, you can draw all the bodies within a collision system. You can also opt to draw individual bodies.
const canvas = document.createElement("canvas");
const context = canvas.getContext("2d");
context.strokeStyle = "#FFFFFF";
context.beginPath();
// draw specific body
body.draw(context);
// draw whole system
system.draw(context);
context.stroke();
To assess the Bounding Volume Hierarchy, you can draw the BVH.
context.strokeStyle = "#FFFFFF";
context.beginPath();
// draw specific body bounding box
body.drawBVH(context);
// draw bounding volume hierarchy of the system
system.drawBVH(context);
context.stroke();
Raycasting
Detect-Collisions provides the functionality to gather raycast data. Here's how:
const start = { x: 0, y: 0 };
const end = { x: 0, y: -10 };
const hit = system.raycast(start, end, (body, ray) => {
// if you don't want the body to be hit by raycast return false
return true;
});
if (hit) {
const { point, body } = hit;
console.log({ point, body });
}
In this example, point
is a Vector
with the coordinates of the nearest intersection, and body
is a reference to the closest body.
Usage in Browsers
Just do what I did here, import from proper cdn as module, and v'oila:
https://code.pietal.dev/#/boilerplate/detect-collisions?pans=html,console
Contributing to the Project
We welcome contributions! Feel free to open a merge request. When doing so, please adhere to the following code style guidelines:
- Execute the
npm run precommit
script prior to submitting your merge request - Follow the conventional commits standard
- Refrain from using the
any
type
Additional Considerations
Why not use a physics engine?
While physics engines like Matter-js or Planck.js are recommended for projects that need comprehensive physics simulation, not all projects require such complexity. In fact, using a physics engine solely for collision detection can lead to unnecessary overhead and complications due to built-in assumptions (gravity, velocity, friction, etc.). Detect-Collisions is purpose-built for efficient and robust collision detection, making it an excellent choice for projects that primarily require this functionality. It can also serve as the foundation for a custom physics engine.
Benchmark
This will provide you with the results of both the insertion test benchmark and a headless Stress Demo benchmark, featuring moving bodies, with increasing amounts in each step.
git clone https://github.com/Prozi/detect-collisions.git
cd detect-collisions
npm i && npm run build # will build & run tests & run benchmarks
License
MIT