tcollide

tcollide is a simple 3D collision detection library for three.js that uses the GJK and EPA algorithms. The current physics model is very simple, something along the lines of:

if (objectsAreColliding()) {
  dont()
}

Nonetheless, maybe it will be useful for some people.

Usage

Install it using npm install tcollide

Creating shapes

Shapes in tcollide are called "supports". A support is a function that given a direction d returns the point on the shape with the highest dot product with d.

Supports can be created using several factory methods. Most methods take an object with the desired properties as an argument. Here are some examples:

import { sphere, box } from 'tcollide'
const myCircle = sphere({ position: [0, 1, 2], radius: 3 })
const myDefaultCircle = sphere({})
const myBox = box({ position: [1, 2, 3], size: [3, 2, 1] })

In addition to basic shapes, tcollide also includes some options for combining shapes. Note that the result of these operations is always another convex shape. On example is the hull(...supports) method, which combines support functions by running each of them on the given vector, and then returning the result with the highest dot product. hull can be used to create a capsule by combining two spheres:

import { sphere, hull } from 'tcollide'
const myCapsule = hull(
  sphere({ position: [0, 1, 0] }),
  sphere({})
)

There is also the sum(...supports) function, which simply adds the result of each support together. This could be used to create cool shapes like a rounded box:

import { sphere, box, sum } from 'tcollide'
const myRoundedBox = sum(sphere({}), box({}))

Creating bodies

A body is a collection of supports that move together. Bodies can be transformed and moved around. Bodies are created using the body factory method:

import { body, sphere } from 'tcollide'
const myBody = body({ supports: [sphere({})], isKinematic: true })

Once you have created a body, you can move it around as much as you like by changing Body.transform, which is a Matrix4 from three.js. Just make sure to call Body.update() after!

myBody.transform.setPosition(1, 2, 3)
myBody.update()

If you want, you can subscribe to changes in the body's position. To do so, use the changed(body) function. This function returns an RxJS observable. Here is an example:

import { changed } from 'tcollide'
changed(myBody).subscribe(() => {
  console.log(myBody.position)
})

Creating scenes

A scene is a collection of bodies. To create a scene and add bodies to it, do this:

import { scene } from 'tcollide'
const myScene = scene({})
myScene.add(myBody)

To increment the physics simulation, run Scene.update(dt), where dt is the elapsed time in seconds. This will trigger changes in all of the bodies. If you subscribed to the changes using changed(body), this callback will be run!

API reference