Contents
What do you need to know about Box2D?
Every Box2D program begins with the creation of a b2World object. b2World is the physics hub that manages memory, objects, and simulation. You can allocate the physics world on the stack, heap, or data section.
When do you create or delete a body in Box2D?
Worlds were briefly mentioned in one of the earlier topics as being the main entity in which all the Box2D bodies live. When you create or delete a body, you call a function of the world object to do this, so the world is managing all the allocations for the objects within it too.
How to change the world settings in Box2D?
To change this you can use b2World::SetAllowSleeping (bool). Once you have a world created as above, you can add bodies into it as we’ve been doing. To make anything interesting happen, we need to repeatedly call the Step function of the world to run the physics simulation.
When to use Box2D and how many iterations?
Typically Box2D is used for fast-paced simulations where an exact solution is not necessary, and at 60 frames per second it’s hard to see little imperfections anyway. So we usually want to set an upper limit on how many iterations to do, to keep the CPU time required reasonable.
What kind of game engine is Box2D written in?
From the game engine’s point of view, a physics engine is just a system for procedural animation. Box2D is written in portable C++. Most of the types defined in the engine begin with the b2 prefix.
How is the Box2D solver used in physics?
Box2D supports the creation of multiple worlds, but this is usually not necessary or desirable. The physics world has a solver that is used to advance time and to resolve contact and joint constraints. The Box2D solver is a high performance iterative solver that operates in order N time, where N is the number of constraints.
What kind of algorithm is used for Box2D?
Box2D uses a computational algorithm called an integrator. Integrators simulate the physics equations at discrete points of time. This goes along with the traditional game loop where we essentially have a flip book of movement on the screen. So we need to pick a time step for Box2D.
How big should a barrel be in Box2D?
Box2D generally works best when objects are the size of typical real world objects. For example, a barrel is about 1 meter tall. Due to the limitations of floating point arithmetic, using Box2D to model the movement of glaciers or dust particles is not a good idea.
Which is an example of a Hello Box2D project?
In the distribution of Box2D is a Hello World project. The program creates a large ground box and a small dynamic box. This code does not contain any graphics. All you will see is text output in the console of the box’s position over time. This is a good example of how to get up and running with Box2D.