# Box2D/Box2D/Common/b2Settings.h File Reference

`#include <cassert>`
`#include <cmath>`

Go to the source code of this file.

## Classes
struct | b2Version
## Defines
#define | B2_NOT_USED(x) ((void)(x))
#define | b2Assert(A) assert(A)
#define | b2_maxFloat FLT_MAX
#define | b2_epsilon FLT_EPSILON
#define | b2_pi 3.14159265359f
#define | b2_maxManifoldPoints 2
| The maximum number of contact points between two convex shapes.
#define | b2_maxPolygonVertices 8
| The maximum number of vertices on a convex polygon.
#define | b2_aabbExtension 0.1f
#define | b2_aabbMultiplier 2.0f
#define | b2_linearSlop 0.005f
#define | b2_angularSlop (2.0f / 180.0f * b2_pi)
#define | b2_polygonRadius (2.0f * b2_linearSlop)
#define | b2_maxTOIContacts 32
| Maximum number of contacts to be handled to solve a TOI impact.
#define | b2_velocityThreshold 1.0f
#define | b2_maxLinearCorrection 0.2f
#define | b2_maxAngularCorrection (8.0f / 180.0f * b2_pi)
#define | b2_maxTranslation 2.0f
#define | b2_maxTranslationSquared (b2_maxTranslation * b2_maxTranslation)
#define | b2_maxRotation (0.5f * b2_pi)
#define | b2_maxRotationSquared (b2_maxRotation * b2_maxRotation)
#define | b2_contactBaumgarte 0.2f
#define | b2_timeToSleep 0.5f
| The time that a body must be still before it will go to sleep.
#define | b2_linearSleepTolerance 0.01f
| A body cannot sleep if its linear velocity is above this tolerance.
#define | b2_angularSleepTolerance (2.0f / 180.0f * b2_pi)
| A body cannot sleep if its angular velocity is above this tolerance.
## Typedefs
typedef signed char | int8
typedef signed short | int16
typedef signed int | int32
typedef unsigned char | uint8
typedef unsigned short | uint16
typedef unsigned int | uint32
typedef float | float32
## Functions
void * | b2Alloc (int32 size)
| Implement this function to use your own memory allocator.
void | b2Free (void *mem)
| If you implement b2Alloc, you should also implement this function.
float32 | b2MixFriction (float32 friction1, float32 friction2)
| Friction mixing law. Feel free to customize this.
float32 | b2MixRestitution (float32 restitution1, float32 restitution2)
| Restitution mixing law. Feel free to customize this.
## Variables
b2Version | b2_version
| Current version.

## Detailed Description

Global tuning constants based on meters-kilograms-seconds (MKS) units.

## Define Documentation

#define b2_aabbExtension 0.1f

This is used to fatten AABBs in the dynamic tree. This allows proxies to move by a small amount without triggering a tree adjustment. This is in meters.

#define b2_aabbMultiplier 2.0f

This is used to fatten AABBs in the dynamic tree. This is used to predict the future position based on the current displacement. This is a dimensionless multiplier.

#define b2_angularSleepTolerance (2.0f / 180.0f * b2_pi)

A body cannot sleep if its angular velocity is above this tolerance.

#define b2_angularSlop (2.0f / 180.0f * b2_pi)

A small angle used as a collision and constraint tolerance. Usually it is chosen to be numerically significant, but visually insignificant.

#define b2_contactBaumgarte 0.2f

This scale factor controls how fast overlap is resolved. Ideally this would be 1 so that overlap is removed in one time step. However using values close to 1 often lead to overshoot.

#define b2_epsilon FLT_EPSILON

#define b2_linearSleepTolerance 0.01f

A body cannot sleep if its linear velocity is above this tolerance.

#define b2_linearSlop 0.005f

A small length used as a collision and constraint tolerance. Usually it is chosen to be numerically significant, but visually insignificant.

#define b2_maxAngularCorrection (8.0f / 180.0f * b2_pi)

The maximum angular position correction used when solving constraints. This helps to prevent overshoot.

#define b2_maxFloat FLT_MAX

#define b2_maxLinearCorrection 0.2f

The maximum linear position correction used when solving constraints. This helps to prevent overshoot.

#define b2_maxManifoldPoints 2

The maximum number of contact points between two convex shapes.

#define b2_maxPolygonVertices 8

The maximum number of vertices on a convex polygon.

#define b2_maxRotation (0.5f * b2_pi)

The maximum angular velocity of a body. This limit is very large and is used to prevent numerical problems. You shouldn't need to adjust this.

#define b2_maxRotationSquared (b2_maxRotation * b2_maxRotation)

#define b2_maxTOIContacts 32

Maximum number of contacts to be handled to solve a TOI impact.

#define b2_maxTranslation 2.0f

The maximum linear velocity of a body. This limit is very large and is used to prevent numerical problems. You shouldn't need to adjust this.

#define b2_maxTranslationSquared (b2_maxTranslation * b2_maxTranslation)

#define B2_NOT_USED | ( | x |  | ) | ((void)(x))

#define b2_pi 3.14159265359f

#define b2_polygonRadius (2.0f * b2_linearSlop)

The radius of the polygon/edge shape skin. This should not be modified. Making this smaller means polygons will have an insufficient buffer for continuous collision. Making it larger may create artifacts for vertex collision.

#define b2_timeToSleep 0.5f

The time that a body must be still before it will go to sleep.

#define b2_velocityThreshold 1.0f

A velocity threshold for elastic collisions. Any collision with a relative linear velocity below this threshold will be treated as inelastic.

#define b2Assert | ( | A |  | ) | assert(A)

## Typedef Documentation

typedef float float32

typedef signed short int16

typedef signed int int32

typedef signed char int8

typedef unsigned short uint16

typedef unsigned int uint32

typedef unsigned char uint8

## Function Documentation

void* b2Alloc | ( | int32 | size | ) |

Implement this function to use your own memory allocator.

void b2Free | ( | void * | mem | ) |

If you implement b2Alloc, you should also implement this function.

float32 b2MixFriction | ( | float32 | friction1,
|  | float32 | friction2 |
| ) |  |  | `[inline]`

Friction mixing law. Feel free to customize this.

float32 b2MixRestitution | ( | float32 | restitution1,
|  | float32 | restitution2 |
| ) |  |  | `[inline]`

Restitution mixing law. Feel free to customize this.

## Variable Documentation

b2Version b2_version

Current version.