Bopit

Simple, quick, AABB framework-independent, collision system. We do rectangles only.

What it Does

• Bopit only does axis-aligned bounding-box (AABB) collisions. If you need anything more complicated than that (circles, polygons, etc.) use another library.
• Handles tunnelling - all items are treated as "bullets". The fact that we only use AABBs allows doing this fast.
• Strives to be fast while being economic in resources
• It's centered on detection, but it also offers some (minimal & basic) collision response
• Can also return the items that touch a point, a segment or a rectangular zone.
• Bopit is gameistic instead of realistic.

Usage

World

import {World, Body} from 'bopit'

const world = new World()
const body = new Body(0, 0, 10, 10)
body.add(world)

new World(cellSize)

Creates a new virtual space for tracking physical interactions split into cells.

• Parameters *

• cellSize Is an optional number. It defaults to 64. It represents the size of the sides of the (squared) cells that will be used internally to provide the data. In tile based games, it's usually a multiple of the tile side size. So in a game where tiles are 32x32, cellSize will be 32, 64 or 128. In more sparse games, it can be higher.

• Returns *

• World

world.queryRect(x, y, width, height)

Queries a rectangle in the world space and will return any bodies that are within that area.

• Parameters *

• x x coordinate, Number
• y y coordinate, Number
• width width of the rectangle, Number
• height height of the rectangle, Number

• Returns *

• [Body] an array of Bodies, will return an empty array if none found

world.queryPoint(x, y)

Queries a single point in the world and will return any bodies under that point.

• Parameters *

• x x coordinate, Number
• y y coordinate, Number

• Returns *

• [Body] an array of Bodies, will return an empty array if none found

world.querySegment(x1, y1, x2, y2)

Queries a line through the space and will return any bodies that are on that line.

• Parameters *

• x x coordinate, Number
• y y coordinate, Number

• Returns *

• [Body] an array of Bodies, will return an empty array if none found

---

new Body(x, y, width, height)

Creates a new physical, rectangular object that can collide with other things.

• Parameters *

• x x coordinate, Number
• y y coordinate, Number
• width width of the rectangle, Number
• height height of the rectangle, Number

• Returns *

• Body

body.add(world)

Adds the body to a world

body.destroy()

Removes the body from the world that it is in.

body.move(x, y, filter)

Will check the collisions and update the position of the body after the collisions

• Parameters *

• x x coordinate, Number
• y y coordinate, Number
• filter Function(body, collision, goalX, goalY)
  • body the body that the check has been run on.
  • collision the collision currently in progress
  • goalX x position of where the body is headed
  • goalY y position of where the body is headed

• Returns *

• finalX the final x resting spot after collisions
• finalY the final y resting spot after collisions
• collisions all of the collision data from collisions that happened along the way

body.check(x, y, filter)

Same as move but without changing the body. This is good for checking before moving.

body.distanceTo(other)

Returns the distance from one body to another

---

Example

Try out the example by running npm i && npm start in the example directory and then opening http://localhost:8080

import {World, Body} from 'bopit'
const world = new World(32)
const body = new Body(120, 120, 20, 20)
body.add(world)
const wall1 = new Body(100, 100, 400, 10, true)
wall1.add(world)

const [finalX, finalY, collisions] = body.move(body.x - 10, body.y - 10)

Thanks to

• kikito https://github.com/kikito/bump.lua for writing such an awesome library that I keep re-writing it in other languages.