Using vector math

The Box2D library uses two-dimensional vectors in a form of its own native data type called b2Vec2. It's used in many places of the Box2D library so it's better to stick with this one.

This data type can be used to specify the position in a 2D space, directional vector with unit size or a speed vector. Keep in mind that Box2D doesn't know the difference between the uses of this vector.

Getting ready

This recipe expects the user to have a basic knowledge of vector math.

The LuaBox2D library contains the b2Vec2 object interface called Vec2. You can create one simply by calling its constructor function. Almost all object constructors are available via the LuaBox2D interface:

local box2d = require 'LuaBox2D'
local Vec2 = box2d.Vec2

This will define a shortcut for the Vec2 object constructor.

How to do it…

You can create a new Vec2 vector object by calling the constructor in one of the following ways:

-- create zero vector
local vector1 = Vec2()
-- create a vector with x=1 and y=2
local...