Our fixtures can be any shape you can imagine or you can combine a variety of different shaped fixtures to make the shape you want.Ī fixture has a shape, density, friction and restitution attached to it. In Box2D our objects are called bodies, and each body is made up of one or more fixtures, which have a fixed position and orientation within the body. The world steps but we don’t see anything as we don’t have anything to interact with it. Now if you run your game it will be pretty boring as nothing happens. The first argument is our Box2D world and the second argument is our libGDX camera. You generally will not use this in a released version of your game, but for testing purposes we will set it up now like so:ĭebugRenderer. The next thing we are going to do is setup our debug renderer. If pixels are used (such as 640 by 480) instead of meters (such as 12 by 9), objects will always move slowly no matter what you do. E.g: drawing a Sprite with a width of 2.0f (2 meters) and using a camera viewportWidth of 20.0f, the Sprite will fill 1/10th of the width on the window.Ī common mistake is measuring your world in pixels instead of meters. To scale up the graphics to make them visible, you should use a camera with a viewportWidth / viewportHeight also in meters. This means drawing a Sprite with a width/height in meters. It is advised to use the same scale you use for Box2D to draw graphics. Generally we want objects to sleep as this conserves CPU usage, but there are situations where you might not want your objects to sleep. The second value in the world creation is a boolean value which tells the world if we want objects to sleep or not. These values can be anything you like, but remember to stick to a constant scale. The first argument we supply is a 2D vector containing the gravity: 0 to indicate no gravity in the horizontal direction, and -10 is a downwards force like in real life (assuming your y axis points upwards). World world = new World ( new Vector2 ( 0, - 10 ), true ) To create the world we use the following code: That said, libGDX does come with a Box2D debug renderer which is extremely handy for debugging your physics simulations, or even for testing your game-play before writing any rendering code. It does not however render the objects for you for that you will use libGDX graphics functions. The world object is basically what holds all your physics objects/bodies and simulates the reactions between them. When setting up Box2D the first thing we need is a world. For backwards compatibility, creating a World for the first time will have the same effect, but using the Box2D class should be preferred. To initialize Box2D it is necessary to call Box2D.init(). Therefore, their documentation may come in handy.īox2D is an extension and not included with libGDX by default. The Box2D implementation in libGDX is a thin Java wrapper around the C++ engine. It is one of the most popular physics libraries for 2D games and has been ported to many languages and many different engines, including libGDX.
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