verlet-system


!img

A tiny 2D/3D verlet physics system.

``js
var Point = require('verlet-point')
var array = require('array-range')
var random = require('randf')

//create a world where points stay within window bounds
var world = require('verlet-system')({
gravity: [0, 500],
min: [0, 0],
max: [width, height]
})

//create 500 points scattered around page
var points = array(500).map(function() {
return Point({
position: [ random(0, width), random(0, height) ]
})
})

//draw our scene
fuction render() {
//step the physics
world.integrate(points, dt)

drawPoints(points)
}
`

Typically used alongside verlet-constraint and verlet-point.

By default, assumes 2D and points with [x, y]. You can require an explicit dimension like so:

`js
var World2D = require('verlet-system/2d') //points [x, y]
var World3D = require('verlet-system/3d') //points [x, y, z]
`

PRs for fixes/improvements welcome.

$3

See the demos folder. The demos are run with beefy.

- triangulate - mouse interactions
- line - using constraints

$3

You can use verlet-point, or just bare objects with the following structure:

`
var point = {
position: [x, y], //required
previous: [x, y], //required
acceleration: [x, y], //required
mass: 1 //optional, will default to 1.0
radius: 25 //optional, will default to 0.0
}
`

Points with a mass of 0 are considered "unmovable". radius is used for collision testing against min and max, but different applications may choose to ignore this.

bounded collisions

Collisions are ignored unless you set a min and/or max vector on the system (with the same number of components as the rest of your points). This will lead to particles 'bouncing' off the collision box. If a component is not a number, it will be ignored (i.e. act as infinity). For example, to allow particles to flow freely horizontally, but restrict them to the 2D window vertically, you might do this:

`js
world.min = [null, 0]
world.max = [null, height]
`

You can also specify a radius on points which will get used in the collision testing. See demo/bounce.js. By default, min and max are null objects, and no collisions are computed.

Usage

![NPM](https://nodei.co/npm/verlet-system/)

#### system = require('verlet-system')([opt])

Creates a new system with the specified options.

- gravity a vector describing the gravity of this system, defaults to a zero vector
- min the minimum bounds vector, defaults to null (i.e. negative infinity)
- max the maximum bounds vector, defaults to null (i.e. positive infinity)
- friction the air friction, defaults to 0.98
- bounce the friction with collision edges, i.e. "bounciness", defaults to 1.0

#### system.integrate(points, step)

Integrates the list of "points" with the given step (typically in seconds).

#### system.integratePoint(point, step)

Integrates a single "point".

running demos

`sh
git clone https://github.com/mattdesl/verlet-system.git
cd verlet-system
npm install

if you haven't got these tools,

npm run build-line
npm run build-triangulate
`

Should work with any tool that consumes CommonJS (i.e. jspm, DuoJS, browserify, webpack).

comparisons

This is not meant to be as feature-complete as choices like verlet-js, PhysicsJS, or matter-js. Some novel goals of this project:

- works in 2D or 3D
- no assumptions about rendering (i.e. works in WebGL, SVG, etc)
- no assumptions about interactions or geometries
- tiny and modular (3kb-6kb depending on what you require), e.g. you may not need constraints (as in the triangulate` demo)
- works on bare objects and arrays, easy to build your own systems on top of
- uses a bounding box rather than just a Y value for "floor"

License

MIT, see LICENSE.md for details.