RK4Spring Class Reference

this class implements a simple dampped spring system using RK4 integration the main motionFunction is derived from http://gafferongames.com/game-physics/spring-physics/ More...

#include <RK4Spring.h>

List of all members.

Public Member Functions
	RK4Spring (ngl::Vector _a, ngl::Vector _b, float _length, float _k, float _damping)
	ctor
void	update ()
	this method calls the integrator to calculate the spring force and updates the spring points, if the points are fixed then no update is made to the points
void	setTimeStep (float _t)
	accessor to set the integration time step (dt)
ngl::Vector	motionFunction (const State &_state, float _t)
	this is going to calculate the spring function F = -k(|x|-d)(x/|x|) - bv where k is the spring constant |x| is the distance between the two spring points d is the distance of seperation b is the coefficient of damping larger b increases the damping force v is the relative velocity between the spring points
void	setAPosition (const ngl::Vector &_a)
	mutator to set the a position of the spring
void	setBPosition (const ngl::Vector &_b)
	mutator to set the b position of the spring
ngl::Vector	getAPosition () const
	accesor for the spring a position
ngl::Vector	getBPosition () const
	accesor for the spring b position
ngl::Vector	getInitialAPosition () const
	accesor for the spring initial a position
ngl::Vector	getInitialBPosition () const
	accesor for the spring initial b position
void	setK (float _k)
	mutator to set the spring constant k
void	setLength (float _l)
	mutator to set the spring resting length
void	setDamping (float _d)
	mutator to set the spring damping co-efficient
void	setAFixed (bool _f)
	mutator to set if the point a is fixed and should not be updated
void	setBFixed (bool _f)
	mutator to set if the point b is fixed and should not be updated
void	reset ()
	re-set the simulation, this will return a and b to the initial values and re-set the time value m_t to 0

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Detailed Description

this class implements a simple dampped spring system using RK4 integration the main motionFunction is derived from http://gafferongames.com/game-physics/spring-physics/

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Constructor & Destructor Documentation

RK4Spring::RK4Spring	(	ngl::Vector	_a,
		ngl::Vector	_b,
		float	_length,
		float	_k,
		float	_damping
	)

ctor

Parameters:

[in]	_a	the start position of spring point a-/\/\/\/
[in]	_b	the start position of spring point -/\/\/\/-b
[in]	_length	the resting length of the spring
[in]	_k	the spring constant from Hooke's law
[in]	_damping	the damping co-efficient of the spring

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Member Function Documentation

ngl::Vector RK4Spring::getAPosition

(

)

const [inline]

accesor for the spring a position

Returns:

m_a the current spring position

ngl::Vector RK4Spring::getBPosition

(

)

const [inline]

accesor for the spring b position

Returns:

m_b the current spring position

ngl::Vector RK4Spring::getInitialAPosition

(

)

const [inline]

accesor for the spring initial a position

Returns:

m_initialA the current spring position

ngl::Vector RK4Spring::getInitialBPosition

(

)

const [inline]

accesor for the spring initial b position

Returns:

m_initialB the current spring position

ngl::Vector RK4Spring::motionFunction	(	const State &	_state,
		float	_t
	)

this is going to calculate the spring function F = -k(|x|-d)(x/|x|) - bv where k is the spring constant |x| is the distance between the two spring points d is the distance of seperation b is the coefficient of damping larger b increases the damping force v is the relative velocity between the spring points

Parameters:

[in]	_state	the state of the spring values to calculate
[in]	_t	the current time state

Returns:

a vector of the force calculated via the RK4 integrator

void RK4Spring::setAFixed

(

bool

_f

)

[inline]

mutator to set if the point a is fixed and should not be updated

Parameters:

[in]

_f

the new value for the point a

void RK4Spring::setAPosition

(

const ngl::Vector &

_a

)

[inline]

mutator to set the a position of the spring

Parameters:

[in]

_a

the value to set

void RK4Spring::setBFixed

(

bool

_f

)

[inline]

mutator to set if the point b is fixed and should not be updated

Parameters:

[in]

_f

the new value for the point b

void RK4Spring::setBPosition

(

const ngl::Vector &

_b

)

[inline]

mutator to set the b position of the spring

Parameters:

[in]

_b

the value to set

void RK4Spring::setDamping

(

float

_d

)

[inline]

mutator to set the spring damping co-efficient

Parameters:

[in]

_d

the new damping value

void RK4Spring::setK

(

float

_k

)

[inline]

mutator to set the spring constant k

Parameters:

[in]

_k

the new k value

void RK4Spring::setLength

(

float

_l

)

[inline]

mutator to set the spring resting length

Parameters:

[in]

_l

the new resting length value

void RK4Spring::setTimeStep

(

float

_t

)

[inline]

accessor to set the integration time step (dt)

Parameters:

[in]

_t

the time step value to use

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The documentation for this class was generated from the following file:

• include/RK4Spring.h