Circle2 NPM | npm.io

circle2

install

npm install circle2

use

new Circle([origin , radius)

Where origin adheres to the following form:

[0, 1]
{ x: 0, y: 1}

and radius is a number

Note: the arguments to the Circle function are optional. If none are passed circle.position will be 0, 0 and circle.radius will be 1

You can also pass in a 3 points and have the circle computed from them:

var circle = Circle([
  [0, 0],
  [10, 0],
  [0, 10]
])

console.log(circle.radius()); // 10
console.log(circle.position); // { x: 0, y: 0 }

or an 3-item array of Vec2

var circle = Circle([
  Vec2(0, 0),
  Vec2(10, 0),
  Vec2(0, 10)
])

console.log(circle.radius()); // 10
console.log(circle.position); // { x: 0, y: 0 }

Note: changing the passed Vec2s will change the circle

Instance Methods

radius(newRadius)

Get/Set the radius of the circle

containsPoint(point)

Where point looks like one of the following:

[0, 1]
{ x: 0, y: 1 }
new Vec2(0, 1)

This function will return true if the passed point is inside or right on the boundary of the circle.

var Circle = require('circle2');

var c = Circle()

console.log(c.contains([10, 0])) // false

c.radius(10);

console.log(c.contains([10, 0])); // true

contains(thing)

Where thing meets the following criteria:

has .position and .radius() - circle
has a function .points() or array .points - polygon
has .x1, .y1, .x2, and .y2 - rectangle
has .x, .y, .w, and .h - rectangle
has .x, .y, .width, and .height - rectangle

This method will return true if the passed thing is completely inside, and false otherwise.

var Circle = require('circle2');

var center = [0, 0];

var c = new Circle(center, 10)
var c2 = new Circle(center, 5)

console.log(c.contains(c2)); // true

Note: if the points of thing are on the circumference of the circle, this method will return true

change(fn)

This is a method that you want to have called any time the circle changes. Either in radius or position

var c = new Circle();

var trackCircleRadius = c.change(function(circle) {
  // do stuff. c === circle
});

c.radius(10); // this will call `trackCircleRadius`

ignore(fn)

Takes an optional fn parameter which if passed will remove the specified listener.

If no fn is passed, all the listeners will be removed.

notify()

Force listeners to be called.

area()

Returns the area PI * r^2

circumference()

Returns the circumference PI * r*2

intersectCircle(circle)

Performs an intersection between this circle and the incoming. Results are as follows: