steer Namespace Reference

All steering functions are templated for easy application to objects inheriting from Agent. Because of this, it is easy to add into any type of design - be it a class hierarchy or a more advanced data structure or system (such as an entity component system). All functions return a steer::steer::Vector2 that can be used to calculate a force with which the entity should be moved given each type of behavior. Combine each calculated force with a weight (any scalar value - but keep it sane or behavior could become strange). Simply multiply each weight, or weights, by the force generated by each behavior's return value to fine-tune it. In addition to the steering functions themselves, this file contains various utilities used by them to perform their work. More...

Classes
class	Agent
	The invisible, but highly necessary, automaton which drives your *game entity/graphical representation's motion. Getters and Setters are provided, *however it will always be easier to just use the data - since it is all public. More...
struct	BehaviorParameters
	Data table with default values used to define variables for guiding steerable objects (agents). More...
class	ArriveComponent
	An example implementation of the arrive steering behavior. The agent will seek the target with a dampened arrival. More...
class	EvadeComponent
	An example implementation of the evasion steering behavior. The agent will flee from the target while predicting it's trajectory. More...
class	FleeComponent
	An example implementation of the flee steering behavior. The agent will flee from the target when it enters its threat range. More...
class	FlockingComponent
	An example implementation of the flocking steering behavior. The agent will interact with other members of the flock utilizing alignment, separation, cohesion, and wandering behaviors. More...
class	HideComponent
	An example implementation of the hiding steering behavior. More...
class	InterposeComponent
	An example implementation of the interpose steering behavior. More...
class	OffsetPursuitComponent
	An example implementation of the offset pursuit steering behavior. More...
class	PathFollowingComponent
	An example implementation of the path following steering behavior. More...
class	PursuitComponent
	An example implementation of the pursuit steering behavior. More...
class	SeekComponent
	An example implementation of the seek steering behavior. More...
class	SuperComponent
	An example implementation of the an agent with every steering behavior implemented. More...
class	WanderComponent
	An example implementation of the wander steering behavior. More...
class	Matrix2D
	A class for 2D matrices and related operations. More...
class	Path
	Class providing the necessary structure for path following behavior. More...
class	SphereObstacle
	Class to aid in obstacle avoidance routine. More...
struct	Vector2
	A 2D vector struct used in many steering calculations. More...
class	VectorMath
	Stateless VectorMath class utilizing static methods to manipulate vectors. Copies of Vector2 are cheap, therefore all functions are "pass by value" at this time. More...
class	Wall
	A class for constructing 2D walls for wall avoidance behaviors. More...

Typedefs
typedef signed char	Int8
	< Useful typedefs for signed/unsigned integers.
typedef unsigned char	Uint8
typedef signed short	Int16
typedef unsigned short	Uint16
typedef signed int	Int32
typedef unsigned int	Uint32
typedef signed long long	Int64
typedef unsigned long long	Uint64
	Useful constants for minimum and maximum values.

Enumerations
enum	behaviorType {   none = 0x00000, seek = 0x00002, flee = 0x00004, arrive = 0x00008,   wander = 0x00010, cohesion = 0x00020, separation = 0x00040, alignment = 0x00080,   obstacleAvoidance = 0x00100, wallAvoidance = 0x00200, followPath = 0x00400, pursuit = 0x00800,   evade = 0x01000, interpose = 0x02000, hide = 0x04000, flock = 0x08000,   offsetPursuit = 0x10000 }
	Bitfield for behavior types. Useful as a representation for combining behaviors.
enum	Deceleration { slow = 3, normal = 2, fast = 1 }
	Useful for applying a scaling factor to deceleration.
enum	summingMethod { weightedSum = 1, prioritized = 2, dithered = 3 }
	Useful for indicating what type of summation method to use for steering forces.
enum	{ clockwise = 1, anticlockwise = -1 }

Functions
template<class T , class conT >
void	TagVehiclesWithinViewRange (const T &entity, const conT &neighbors, float viewDistance)
template<class T , class conT >
void	TagObstaclesWithinViewRange (const T &entity, const conT &obstacles, float boxLength)
template<class T , class conT >
void	TagNeighbors (const T &entity, const conT &neighbors, float radius)
template<class T , class conT >
void	TagObstacles (const T &entity, const conT &obstacles, float radius)
bool	TwoCirclesOverlapped (float x1, float y1, float r1, float x2, float y2, float r2)
	Tests for circle-to-circle overlap.
bool	TwoCirclesOverlapped (Vector2 c1, float r1, Vector2 c2, float r2)
	Tests for circle-to-circle overlap.
template<class T , class conT >
bool	Overlapped (const T *ob, const conT &conOb, float MinDistBetweenObstacles)
bool	LineIntersection2D (steer::Vector2 A, steer::Vector2 B, steer::Vector2 C, steer::Vector2 D, float &dist, steer::Vector2 &point)
	Checks for an intersection between two lines, given beginning and end points for both lines.
void	WrapAround (steer::Vector2 &pos, int MaxX, int MaxY)
	Calculates the vector useful for wrapping around the steering vector of an agent to fit in the bounds of a rectangle (the screen, for example).
template<class T , class N >
steer::Vector2	calculateTarget (const T &agent, const N &other)
template<class T , class N , class P >
steer::Vector2	calculateTarget (const T &agent, const N &otherA, const P &otherB)
template<class T >
steer::Vector2	Seek (const T &agent)
template<class T >
steer::Vector2	Seek (const T &agent, steer::Vector2 target)
	A function returning the value necessary to steer an agent towards a target.
template<class T , class conT >
steer::Vector2	Alignment (const T &agent, const conT &neighbors)
template<class T , class conT >
steer::Vector2	Separation (const T &agent, const conT &neighbors)
template<class T , class conT >
steer::Vector2	Cohesion (const T &agent, const conT &neighbors)
template<class T >
steer::Vector2	Arrive (const T &agent, Uint32 deceleration)
template<class T , class N >
steer::Vector2	Pursuit (const T &agent, const N &evader)
template<class T , class N >
steer::Vector2	OffsetPursuit (const T &agent, const N &leader, const steer::BehaviorParameters &parameters)
template<class T >
steer::Vector2	Flee (const T &agent)
template<class T , class N >
steer::Vector2	Evade (const T &agent, const N &other)
steer::Vector2	findPosition (const steer::Vector2 &goalPosition, const float radius, const steer::Vector2 &avoidPosition, float distanceBuffer)
	This function calculates a position located on the other side of some position in space, given a radius, that is out of reach from an undesirable position (for example, a pursuing agent).
template<class T , class N , class conT >
steer::Vector2	Hide (const T &agent, const N &other, const conT &obstacles, const steer::BehaviorParameters &parameters)
template<class T , class N , class P >
steer::Vector2	Interpose (const T &agent, const N &otherA, const P &otherB, const steer::BehaviorParameters &parameters)
template<class T >
steer::Vector2	Wander (const T &agent)
template<class T , class conT >
steer::Vector2	ObstacleAvoidance (const T &agent, const conT &obstacles, const steer::BehaviorParameters &parameters)
template<class T >
steer::Vector2	WallAvoidance (const T &agent, const std::vector< steer::Wall * > &walls)
template<class T >
steer::Vector2	PathFollowing (const T &agent, steer::Path *path, const steer::BehaviorParameters &params)
std::vector< steer::Vector2 >	WorldTransform (std::vector< steer::Vector2 > &points, const steer::Vector2 &pos, const steer::Vector2 &forward, const steer::Vector2 &side, const steer::Vector2 &scale)
	Given a std::vector of steer::Vector2, a position, orientation, and scale, this function transforms the std::vector of steer::Vector2 into the object's world space.
std::vector< steer::Vector2 >	WorldTransform (std::vector< steer::Vector2 > &points, const steer::Vector2 &pos, const steer::Vector2 &forward, const steer::Vector2 &side)
	Given a std::vector of steer::Vector2, a position, and orientation, this function transforms the std::vector of steer::Vector2 into the object's world space.
steer::Vector2	PointToWorldSpace (const steer::Vector2 &point, const steer::Vector2 &AgentHeading, const steer::Vector2 &AgentSide, const steer::Vector2 &AgentPosition)
	Transforms a point from the agent's local space into world space.
steer::Vector2	VectorToWorldSpace (const steer::Vector2 &vec, const steer::Vector2 &AgentHeading, const steer::Vector2 &AgentSide)
	Transforms a vector from the agent's local space into world space.
steer::Vector2	PointToLocalSpace (const steer::Vector2 &point, const steer::Vector2 &AgentHeading, const steer::Vector2 &AgentSide, const steer::Vector2 &AgentPosition)
	Transforms a vector from world space into the agent's local space.
steer::Vector2	VectorToLocalSpace (const steer::Vector2 &vec, const steer::Vector2 &AgentHeading, const steer::Vector2 &AgentSide)
	Transforms a vector from world space into the agent's local space.
void	Vec2DRotateAroundOrigin (steer::Vector2 &v, float ang)
	Rotates a vector by an angle in radians around the origin.
std::vector< steer::Vector2 >	CreateWhiskers (unsigned int NumWhiskers, float WhiskerLength, float fov, steer::Vector2 facing, steer::Vector2 origin)
	Given an origin, a facing direction, a 'field of view' describing the limit of the outer whiskers, a whisker length and the number of whiskers this method returns a vector containing the end positions of a series of whiskers radiating away from the origin and with equal distance between them. (like the spokes of a wheel clipped to a specific segment size);.
template<typename T >
bool	isNaN (T val)
float	DegreesToRadians (float degrees)
bool	IsZero (float val)
	Returns true if the parameter is equal to zero.
bool	InRange (float start, float end, float val)
	Returns true if the third parameter is in the range described by the first two parameters.
template<class T >
T	Maximum (const T &v1, const T &v2)
int	RandInt (int x, int y)
	Returns a random integer between x and y.
float	RandFloat ()
	Returns a random float between 1 and the maximum value for a float.
float	RandInRange (float x, float y)
	Returns a random float between x and y.
bool	RandBool ()
	Returns true or false randomly.
float	RandomClamped ()
	Returns a random float in the range -1 < n < 1.
float	RandGaussian (float mean=0.0, float standard_deviation=1.0)
	Returns a random number with a normal distribution. See method at http://www.taygeta.com/random/gaussian.html.
float	Sigmoid (float input, float response=1.0)
	Returns a value from the sigmoid (S-curve) function based on input and response.
template<class T >
T	MaxOf (const T &a, const T &b)
template<class T >
T	MinOf (const T &a, const T &b)
template<class T , class U , class V >
void	Clamp (T &arg, const U &minVal, const V &maxVal)
int	Rounded (float val)
	Rounds a double up or down depending on its value.
int	RoundUnderOffset (float val, float offset)
	rounds a double up or down depending on whether its mantissa is higher or lower than offset.
bool	isEqual (float a, float b)
	Compares two real numbers. Returns true if they are equal.
bool	isEqual (double a, double b)
	Compares two real numbers. Returns true if they are equal.
template<class T >
float	Average (const std::vector< T > &v)
float	StandardDeviation (const std::vector< float > &v)
	Finds the standard deviation from a std::vector of floats.
template<class container >
void	DeleteSTLContainer (container &c)
template<class map >
void	DeleteSTLMap (map &m)
Vector2	operator* (const Vector2 &lhs, double rhs)
Vector2	operator* (double lhs, const Vector2 &rhs)
Vector2	operator- (const Vector2 &lhs, const Vector2 &rhs)
Vector2	operator+ (const Vector2 &lhs, const Vector2 &rhs)
Vector2	operator/ (const Vector2 &lhs, double val)
Vector2	Vec2DNormalize (const Vector2 &v)
double	Vec2DDistance (const Vector2 &v1, const Vector2 &v2)
double	Vec2DDistanceSq (const Vector2 &v1, const Vector2 &v2)
double	Vec2DLength (const Vector2 &v)
double	Vec2DLengthSq (const Vector2 &v)
bool	NotInsideRegion (Vector2 p, Vector2 top_left, Vector2 bot_rgt)
bool	InsideRegion (Vector2 p, Vector2 top_left, Vector2 bot_rgt)
bool	InsideRegion (Vector2 p, int left, int top, int right, int bottom)
bool	isSecondInFOVOfFirst (Vector2 posFirst, Vector2 facingFirst, Vector2 posSecond, double fov)

Variables
const int	MaxInt = (std::numeric_limits<int>::max)()
const double	MaxDouble = (std::numeric_limits<double>::max)()
const double	MinDouble = (std::numeric_limits<double>::min)()
const float	MaxFloat = (std::numeric_limits<float>::max)()
const float	MinFloat = (std::numeric_limits<float>::min)()
	Useful constants for Pi.
const float	Pi = 3.14159f
const float	TwoPi = Pi * 2
const float	HalfPi = Pi / 2
const float	QuarterPi = Pi / 4

Detailed Description

All steering functions are templated for easy application to objects inheriting from Agent. Because of this, it is easy to add into any type of design - be it a class hierarchy or a more advanced data structure or system (such as an entity component system). All functions return a steer::steer::Vector2 that can be used to calculate a force with which the entity should be moved given each type of behavior. Combine each calculated force with a weight (any scalar value - but keep it sane or behavior could become strange). Simply multiply each weight, or weights, by the force generated by each behavior's return value to fine-tune it. In addition to the steering functions themselves, this file contains various utilities used by them to perform their work.

Function Documentation

std::vector< steer::Vector2 > steer::CreateWhiskers ( unsigned int  NumWhiskers, float  WhiskerLength, float  fov, steer::Vector2  facing, steer::Vector2  origin  )

inline

Given an origin, a facing direction, a 'field of view' describing the limit of the outer whiskers, a whisker length and the number of whiskers this method returns a vector containing the end positions of a series of whiskers radiating away from the origin and with equal distance between them. (like the spokes of a wheel clipped to a specific segment size);.

Parameters

NumWhiskers	- a plain old unsigned int.
WhiskerLength	- a plain old float.
facing	- a steer::Vector2 of floats.
origin	- a steer::Vector2 of floats.

steer::Vector2 steer::findPosition ( const steer::Vector2 &  goalPosition, const float  radius, const steer::Vector2 &  avoidPosition, float  distanceBuffer  )

inline

This function calculates a position located on the other side of some position in space, given a radius, that is out of reach from an undesirable position (for example, a pursuing agent).

Parameters

goalPosition	- a 2D vector of doubles.
radius	- a plain old float.
avoidPosition	- a 2D vector of doubles.
boundary	- a plain old float.

bool steer::InRange ( float  start, float  end, float  val  )

inline

Returns true if the third parameter is in the range described by the first two parameters.

Parameters

start	- a plain old float.
end	- a plain old float.
val	- a plain old float.

bool steer::isEqual ( float  a, float  b  )

inline

Compares two real numbers. Returns true if they are equal.

Parameters

a	- a plain old float.
b	- a plain old float.

bool steer::isEqual ( double  a, double  b  )

inline

Compares two real numbers. Returns true if they are equal.

Parameters

a	- a plain old double.
b	- a plain old double.

bool steer::IsZero ( float  val )

inline

Returns true if the parameter is equal to zero.

Parameters

val	- a plain old float.

bool steer::LineIntersection2D ( steer::Vector2  A, steer::Vector2  B, steer::Vector2  C, steer::Vector2  D, float &  dist, steer::Vector2 &  point  )

inline

Checks for an intersection between two lines, given beginning and end points for both lines.

Parameters

A	- a 2D vector of floats.
B	- a 2D vector of floats.
C	- a 2D vector of floats.
D	- a 2D vector of floats.
dist	- a plain old float.
point	- a 2D vector of floats.

steer::Vector2 steer::PointToLocalSpace ( const steer::Vector2 &  point, const steer::Vector2 &  AgentHeading, const steer::Vector2 &  AgentSide, const steer::Vector2 &  AgentPosition  )

inline

Transforms a vector from world space into the agent's local space.

Parameters

point	- a steer::Vector2 of floats.
AgentHeading	- a steer::Vector2 of floats.
AgentSide	- a steer::Vector2 of floats.
AgentPosition	- a steer::Vector2 of floats.

steer::Vector2 steer::PointToWorldSpace ( const steer::Vector2 &  point, const steer::Vector2 &  AgentHeading, const steer::Vector2 &  AgentSide, const steer::Vector2 &  AgentPosition  )

inline

Transforms a point from the agent's local space into world space.

Parameters

point	- a steer::Vector2 of floats.
AgentHeading	- a steer::Vector2 of floats.
AgentSide	- a steer::Vector2 of floats.
AgentPosition	- a steer::Vector2 of floats.

float steer::RandGaussian ( float  mean = 0.0, float  standard_deviation = 1.0  )

inline

Returns a random number with a normal distribution. See method at http://www.taygeta.com/random/gaussian.html.

Parameters

mean	- a plain old float.
standard_deviation	- a plain old float.

float steer::RandInRange ( float  x, float  y  )

inline

Returns a random float between x and y.

Parameters

x	- a plain old float.
y	- a plain old float.

int steer::RandInt ( int  x, int  y  )

inline

Returns a random integer between x and y.

Parameters

x	- a plain old int.
y	- a plain old int.

int steer::Rounded ( float  val )

inline

Rounds a double up or down depending on its value.

Parameters

val	- a plain old float.

int steer::RoundUnderOffset ( float  val, float  offset  )

inline

rounds a double up or down depending on whether its mantissa is higher or lower than offset.

Parameters

val	- a plain old float.
offset	- a plain old float.

template<class T >

steer::Vector2 steer::Seek	(	const T &	agent,
		steer::Vector2	target
	)

A function returning the value necessary to steer an agent towards a target.

Parameters

agent	- a steer::Agent derived object.
target	- the target vector you are trying to reach.

float steer::Sigmoid ( float  input, float  response = 1.0  )

inline

Returns a value from the sigmoid (S-curve) function based on input and response.

Parameters

input	- a plain old float.
response	- a plain old float.

float steer::StandardDeviation ( const std::vector< float > &  v )

inline

Finds the standard deviation from a std::vector of floats.

Parameters

v	- a std::vector of floats.

bool steer::TwoCirclesOverlapped ( float  x1, float  y1, float  r1, float  x2, float  y2, float  r2  )

inline

Tests for circle-to-circle overlap.

Parameters

x1	- a plain old float.
y1	- a plain old float.
r1	- a plain old float.
x2	- a plain old float.
y2	- a plain old float.
r2	- a plain old float.

bool steer::TwoCirclesOverlapped ( Vector2  c1, float  r1, Vector2  c2, float  r2  )

inline

Tests for circle-to-circle overlap.

Parameters

c1	- a plain old float.
r1	- a plain old float.
c2	- a plain old float.
r2	- a plain old float.

void steer::Vec2DRotateAroundOrigin ( steer::Vector2 &  v, float  ang  )

inline

Rotates a vector by an angle in radians around the origin.

Parameters

v	- a steer::Vector2 of floats.
ang	- a plain old float.

steer::Vector2 steer::VectorToLocalSpace ( const steer::Vector2 &  vec, const steer::Vector2 &  AgentHeading, const steer::Vector2 &  AgentSide  )

inline

Transforms a vector from world space into the agent's local space.

Parameters

vec	- a steer::Vector2 of floats.
AgentHeading	- a steer::Vector2 of floats.
AgentSide	- a steer::Vector2 of floats.

steer::Vector2 steer::VectorToWorldSpace ( const steer::Vector2 &  vec, const steer::Vector2 &  AgentHeading, const steer::Vector2 &  AgentSide  )

inline

Transforms a vector from the agent's local space into world space.

Parameters

vec	- a steer::Vector2 of floats.
AgentHeading	- a steer::Vector2 of floats.
AgentSide	- a steer::Vector2 of floats.

std::vector< steer::Vector2 > steer::WorldTransform ( std::vector< steer::Vector2 > &  points, const steer::Vector2 &  pos, const steer::Vector2 &  forward, const steer::Vector2 &  side, const steer::Vector2 &  scale  )

inline

Given a std::vector of steer::Vector2, a position, orientation, and scale, this function transforms the std::vector of steer::Vector2 into the object's world space.

Parameters

points	- a std::vector of steer::Vector2 floats.
pos	- a steer::Vector2 of floats.
forward	- a steer::Vector2 of floats.
side	- a steer::Vector2 of floats.
scale	- a steer::Vector2 of floats.

std::vector< steer::Vector2 > steer::WorldTransform ( std::vector< steer::Vector2 > &  points, const steer::Vector2 &  pos, const steer::Vector2 &  forward, const steer::Vector2 &  side  )

inline

Given a std::vector of steer::Vector2, a position, and orientation, this function transforms the std::vector of steer::Vector2 into the object's world space.

Parameters

points	- a std::vector of steer::Vector2.
pos	- a steer::Vector2 of floats.
forward	- a steer::Vector2 of floats.
side	- a steer::Vector2 of floats.

void steer::WrapAround ( steer::Vector2 &  pos, int  MaxX, int  MaxY  )

inline

Calculates the vector useful for wrapping around the steering vector of an agent to fit in the bounds of a rectangle (the screen, for example).

Parameters

pos	- a 2D vector of floats.
MaxX	- a plain old int.
MaxY	- a plain old int.