Physics Engine: Box2D

Box2D Stats
Developer: Erin Catto
Cost: Free, open-source
Programming Language: C++

Box2D is is an open-source physics and graphics engine for two-dimensional games created by Erin Catto in 2006. Features include:

  • Continuous Collision Detection
  • Rigid Body Dynamics
  • Gravity
  • Friction
  • Restitution

Box2D has become the basis for many other engines, including Cocos2D for iPhone, Chipmunk, and Torque2D



Gravity is a vital portion of 3D video games and simulations, as the environment cannot mimic real physics without gravity. Without gravity, characters and objects will not be able to properly move, jump, or fall, because gravity is an essential piece of many motion equations. In most situations, a complete Physics Engine is optimal, as it factors in gravity along with other components – collision detection, rotation calculations, rigid body dynamics, Brownian motion, et cetera), however it is not required. Algorithms for gravity have been written and open sourced for many languages and can be easily found on services like GitHub, Google Code, and SourceForge.

The Force of Gravity equals 9.8 m/s2, so if a character starts falling from rest, his speed will increase according to the time elapsed squared times the force of gravity. The speed can then be used to calculate how much damage must be applied to the character, so falling for one second doesn’t hurt the player as much as falling for 4 seconds, which adds an additional dynamic to gameplay.


About this Blog
Welcome to the Unlimited Physics blog! This weekly blog will look at all kinds of awesome Physics and Physics applications.
I don’t want this blog to turn into just reviews. I see this blog analyzing different uses of physics and different kinds of physics and their benefits. However, I will look at different uses from the real world and point out what physics are being used and how.

About Me
My name is Justin Etzine, and I’m a High School Junior at Posnack in South Florida. I love technology and engineering. I’ve been programming since fifth grade, and since expanded from just computer science into engineering in general.