#include <SpringMath.h>

Static Public Member Functions
static constexpr float	SmoothingTimeToHalfLife (float SmoothingTime)

static constexpr float	HalfLifeToSmoothingTime (float HalfLife)

static constexpr float	SmoothingTimeToStrength (float SmoothingTime)

static constexpr float	StrengthToSmoothingTime (float Strength)

template<typename T >
static void	CriticalSpringDamper (T &InOutX, T &InOutV, T TargetX, float SmoothingTime, float DeltaTime)

static void	CriticalSpringDamperAngle (float &InOutAngleRadians, float &InOutAngularVelocityRadians, float TargetAngleRadians, float SmoothingTime, float DeltaTime)

static void	CriticalSpringDamperQuat (FQuat &InOutRotation, FVector &InOutAngularVelocityRadians, const FQuat &TargetRotation, float SmoothingTime, float DeltaTime)

template<typename TFloat >
static void	VelocitySpringDamperF (TFloat &InOutX, TFloat &InOutV, TFloat &InOutXi, TFloat TargetX, TFloat MaxSpeed, float SmoothingTime, float DeltaTime)

template<typename TVector >
static void	VelocitySpringDamper (TVector &InOutX, TVector &InOutV, TVector &InOutXi, TVector TargetX, float MaxSpeed, float SmoothingTime, float DeltaTime)

template<typename TVector >
static void	SpringCharacterUpdate (TVector &InOutPosition, TVector &InOutVelocity, TVector &InOutAcceleration, const TVector &TargetVelocity, float SmoothingTime, float DeltaTime, float VDeadzone=1e-2f, float ADeadzone=1e-4f)

template<typename TVector >
static void	SpringCharacterPredict (TArrayView< TVector > OutPredictedPositions, TArrayView< TVector > OutPredictedVelocities, TArrayView< TVector > OutPredictedAccelerations, const TVector &CurrentPosition, const TVector &CurrentVelocity, const TVector &CurrentAcceleration, const TVector &TargetVelocity, float SmoothingTime, float SecondsPerPredictionStep, float VDeadzone=1e-2f, float ADeadzone=1e-4f)

template<typename TVector >
static void	VelocitySpringCharacterUpdate (TVector &InOutPosition, TVector &InOutVelocity, TVector &InOutVelocityIntermediate, TVector &InOutAcceleration, TVector TargetVelocity, float SmoothingTime, float MaxAcceleration, float DeltaTime, float VDeadzone=1e-2f, float ADeadzone=1e-4f)

template<typename TVector >
static void	VelocitySpringCharacterPredict (TArrayView< TVector > OutPredictedPositions, TArrayView< TVector > OutPredictedVelocities, TArrayView< TVector > OutPredictedIntermediateVelocities, TArrayView< TVector > OutPredictedAccelerations, const TVector &CurrentPosition, const TVector &CurrentVelocity, const TVector &CurrentIntermediateVelocity, const TVector &CurrentAcceleration, const TVector &TargetVelocity, float SmoothingTime, float MaxAcceleration, float SecondsPerPredictionStep, float VDeadzone=1e-2f, float ADeadzone=1e-4f)

static void	CriticalSpringDamperQuatPredict (TArrayView< FQuat > OutPredictedRotations, TArrayView< FVector > OutPredictedAngularVelocities, int32 PredictCount, const FQuat &CurrentRotation, const FVector &CurrentAngularVelocity, const FQuat &TargetRotation, float SmoothingTime, float SecondsPerPredictionStep)

static constexpr void	ExponentialSmoothingApproxQuat (FQuat &InOutRotation, const FQuat &InTargetRotation, const float InDeltaTime, const float InSmoothingTime)

static constexpr void	ExponentialSmoothingApproxAngle (float &InOutAngleRadians, const float &InTargetAngleRadians, const float InDeltaTime, const float InSmoothingTime)

Member Function Documentation

◆ CriticalSpringDamper()

template<typename T >

static void SpringMath::CriticalSpringDamper	(	T &	InOutX,
		T &	InOutV,
		T	TargetX,
		float	SmoothingTime,
		float	DeltaTime
	)

inlinestatic

Simplified version of FMath::CriticallyDampedSmoothing where v_goal is assumed to be 0. This interpolates the value InOutX towards TargetX with the motion of a critically damped spring. The velocity of InOutX is stored in InOutV.

Template Parameters

T	The type to be damped

Parameters

InOutX	The value to be damped
InOutV	The speed of the value to be damped
TargetX	The goal to damp towards
SmoothingTime	The smoothing time to use for the spring. Longer times lead to more damped behaviour. A time of 0 will snap InOutX to TargetX
DeltaTime	Timestep in seconds

◆ CriticalSpringDamperAngle()

static void SpringMath::CriticalSpringDamperAngle	(	float &	InOutAngleRadians,
		float &	InOutAngularVelocityRadians,
		float	TargetAngleRadians,
		float	SmoothingTime,
		float	DeltaTime
	)

inlinestatic

Specialized angle version of CriticalSpringDamper that handles angle wrapping.

Parameters

InOutAngleRadians	The value to be damped
InOutAngularVelocityRadians	The speed of the value to be damped
TargetAngleRadians	The goal to damp towards
SmoothingTime	The smoothing time to use for the spring. Longer times lead to more damped behaviour. A time of 0 will snap InOutAngleRadians to TargetAngleRadians
DeltaTime	Timestep in seconds

◆ CriticalSpringDamperQuat()

static void SpringMath::CriticalSpringDamperQuat	(	FQuat &	InOutRotation,
		FVector &	InOutAngularVelocityRadians,
		const FQuat &	TargetRotation,
		float	SmoothingTime,
		float	DeltaTime
	)

inlinestatic

Specialized quaternion version of CriticalSpringDamper, uses FVector for angular velocity

Parameters

InOutRotation	The value to be damped
InOutAngularVelocityRadians	The angular velocity of the rotation in radians
TargetRotation	The target rotation to damp towards
SmoothingTime	he smoothing time to use for the spring. Longer times lead to more damped behaviour. A time of 0 will snap InOutRotation to TargetRotation
DeltaTime

◆ CriticalSpringDamperQuatPredict()

static void SpringMath::CriticalSpringDamperQuatPredict	(	TArrayView< FQuat >	OutPredictedRotations,
		TArrayView< FVector >	OutPredictedAngularVelocities,
		int32	PredictCount,
		const FQuat &	CurrentRotation,
		const FVector &	CurrentAngularVelocity,
		const FQuat &	TargetRotation,
		float	SmoothingTime,
		float	SecondsPerPredictionStep
	)

inlinestatic

Prediction of CriticalSpringDamperQuat

Parameters

OutPredictedRotations	ArrayView of output buffer to put the predicted rotations. ArrayView should be the same size as PredictCount
OutPredictedAngularVelocities	ArrayView of output buffer to put the predicted angular velocities. ArrayView should be the same size as PredictCount
PredictCount	How many points to predict. Must be greater than 0
CurrentRotation	Initial rotation at t = 0
CurrentAngularVelocity	Initial angular velocity at t = 0
TargetRotation	The target rotation
SmoothingTime	The smoothing time
SecondsPerPredictionStep	How many seconds per prediction step

◆ ExponentialSmoothingApproxAngle()

static constexpr void SpringMath::ExponentialSmoothingApproxAngle	(	float &	InOutAngleRadians,
		const float &	InTargetAngleRadians,
		const float	InDeltaTime,
		const float	InSmoothingTime
	)

inlinestaticconstexpr

Specialized angle damper, similar to FMath::ExponentialSmoothingApprox but deals correctly with angle wrap-around. Smooths an angle using exponential damping towards a target.

Parameters

InOutAngleRadians	The angle to be smoothed
InTargetAngleRadians	The target to smooth towards
InDeltaTime	Time interval
InSmoothingTime	Timescale over which to smooth. Larger values result in more smoothed behaviour. Can be zero.

◆ ExponentialSmoothingApproxQuat()

static constexpr void SpringMath::ExponentialSmoothingApproxQuat	(	FQuat &	InOutRotation,
		const FQuat &	InTargetRotation,
		const float	InDeltaTime,
		const float	InSmoothingTime
	)

inlinestaticconstexpr

Specialized quaternion damper, similar to FMath::ExponentialSmoothingApprox but for quaternions. Smooths a value using exponential damping towards a target.

Parameters

InOutRotation	The value to be smoothed
InTargetRotation	The target to smooth towards
InDeltaTime	Time interval
InSmoothingTime	Timescale over which to smooth. Larger values result in more smoothed behaviour. Can be zero.

◆ HalfLifeToSmoothingTime()

static constexpr float SpringMath::HalfLifeToSmoothingTime ( float HalfLife )

inlinestaticconstexpr

Convert a halflife to a smoothing time

Parameters

HalfLife The half life of the spring. How long it takes the value to get halfway towards the target.

Returns: The smoothing time of the spring in seconds. It is the time by which the output lags the input when critically damped, when the input is changing at a constant rate.

◆ SmoothingTimeToHalfLife()

static constexpr float SpringMath::SmoothingTimeToHalfLife ( float SmoothingTime )

inlinestaticconstexpr

Convert a smoothing time to a half life

Parameters

SmoothingTime The smoothing time of the spring in seconds. It is the time by which the output lags the input when critically damped, when the input is changing at a constant rate.

Returns: The half life of the spring. How long it takes the value to get halfway towards the target.

◆ SmoothingTimeToStrength()

static constexpr float SpringMath::SmoothingTimeToStrength ( float SmoothingTime )

inlinestaticconstexpr

Convert from smoothing time to spring strength.

Parameters

SmoothingTime The smoothing time of the spring in seconds. It is the time by which the output lags the input when critically damped, when the input is changing at a constant rate.

Returns: The spring strength. This corresponds to the undamped frequency of the spring in hz.

◆ SpringCharacterPredict()

template<typename TVector >

static void SpringMath::SpringCharacterPredict	(	TArrayView< TVector >	OutPredictedPositions,
		TArrayView< TVector >	OutPredictedVelocities,
		TArrayView< TVector >	OutPredictedAccelerations,
		const TVector &	CurrentPosition,
		const TVector &	CurrentVelocity,
		const TVector &	CurrentAcceleration,
		const TVector &	TargetVelocity,
		float	SmoothingTime,
		float	SecondsPerPredictionStep,
		float	VDeadzone = `1e-2f`,
		float	ADeadzone = `1e-4f`
	)

inlinestatic

Gives predicted positions, velocities and accelerations for SpringCharacterUpdate. Useful for generating a predicted trajectory given known initial start conditions.

Template Parameters

TVector The type of vector to use (e.g. FVector2D, FVector4, FVector etc)

Parameters

OutPredictedPositions	ArrayView of output buffer to put the predicted positions. ArrayView should be the same size as PredictCount
OutPredictedVelocities	ArrayView of output buffer to put the predicted velocities. ArrayView should be the same size as PredictCount
OutPredictedAccelerations	ArrayView of output buffer to put the predicted accelerations. ArrayView should be the same size as PredictCount
PredictCount	How many points to predict. Must be greater than 0
CurrentPosition	The initial position of the character
CurrentVelocity	The initial velocity of the character
CurrentAcceleration	The initial acceleration of the character
TargetVelocity	The target velocity of the character
SmoothingTime	The smoothing time of the character. It takes roughly the smoothing time in order for the character to reach the target velocity.
SecondsPerPredictionStep	How much time in between each prediction step.
VDeadzone	Deadzone for velocity. Current velocity will snap to target velocity when within the deadzone
ADeadzone	Deadzone for acceleration. Acceleration will snap to zero when within the deadzone

◆ SpringCharacterUpdate()

template<typename TVector >

static void SpringMath::SpringCharacterUpdate	(	TVector &	InOutPosition,
		TVector &	InOutVelocity,
		TVector &	InOutAcceleration,
		const TVector &	TargetVelocity,
		float	SmoothingTime,
		float	DeltaTime,
		float	VDeadzone = `1e-2f`,
		float	ADeadzone = `1e-4f`
	)

inlinestatic

Update the position of a character given a target velocity using a simple damped spring

Template Parameters

TVector The type of vector to use (e.g. FVector2D, FVector4, FVector etc)

Parameters

InOutPosition	The position of the character
InOutVelocity	The velocity of the character. Needs to be stored and persisted by the caller. Usually initialized to zero and not modified by the caller.
InOutAcceleration	The acceleration of the character. Needs to be stored and persisted by the caller. Usually initialized to zero and not modified by the caller.
TargetVelocity	The target velocity of the character.
SmoothingTime	The time over which to smooth velocity. It takes roughly the smoothing time in order for the character to reach the target velocity.
DeltaTime	The delta time to tick the character
VDeadzone	Deadzone for velocity. Current velocity will snap to target velocity when within the deadzone
ADeadzone	Deadzone for acceleration. Acceleration will snap to zero when within the deadzone

◆ StrengthToSmoothingTime()

static constexpr float SpringMath::StrengthToSmoothingTime ( float Strength )

inlinestaticconstexpr

Convert from spring strength to smoothing time.

Parameters

Strength The spring strength. This corresponds to the undamped frequency of the spring in hz.

Returns: The smoothing time of the spring in seconds. It is the time by which the output lags the input when critically damped, when the input is changing at a constant rate.

◆ VelocitySpringCharacterPredict()

template<typename TVector >

static void SpringMath::VelocitySpringCharacterPredict	(	TArrayView< TVector >	OutPredictedPositions,
		TArrayView< TVector >	OutPredictedVelocities,
		TArrayView< TVector >	OutPredictedIntermediateVelocities,
		TArrayView< TVector >	OutPredictedAccelerations,
		const TVector &	CurrentPosition,
		const TVector &	CurrentVelocity,
		const TVector &	CurrentIntermediateVelocity,
		const TVector &	CurrentAcceleration,
		const TVector &	TargetVelocity,
		float	SmoothingTime,
		float	MaxAcceleration,
		float	SecondsPerPredictionStep,
		float	VDeadzone = `1e-2f`,
		float	ADeadzone = `1e-4f`
	)

inlinestatic

Gives predicted positions, velocities and accelerations for SpringCharacterUpdate. Useful for generating a predicted trajectory given known initial start conditions.

Template Parameters

TVector The type of vector to use (e.g. FVector2D, FVector4, FVector etc)

Parameters

OutPredictedPositions	ArrayView of output buffer to put the predicted positions. ArrayView should be the same size as PredictCount
OutPredictedVelocities	ArrayView of output buffer to put the predicted velocities. ArrayView should be the same size as PredictCount
OutPredictedIntermediateVelocities	ArrayView of output buffer to put the predicted intermediate velocities. ArrayView should be the same size as PredictCount
OutPredictedAccelerations	ArrayView of output buffer to put the predicted accelerations. ArrayView should be the same size as PredictCount
PredictCount	How many points to predict. Must be greater than 0
CurrentPosition	The initial position of the character
CurrentVelocity	The initial velocity of the character
CurrentIntermediateVelocity	The initial intermediate velocity of the character
CurrentAcceleration	The initial acceleration of the character
TargetVelocity	The target velocity of the character
SmoothingTime	The smoothing time of the character. It takes roughly the smoothing time in order for the character to reach the target velocity.
MaxAcceleration	Puts a limit on the maximum acceleration that the intermediate velocity can do each frame. If MaxAccel is very large, the behaviour wil lbe the same as SpringCharacterUpdate
SecondsPerPredictionStep	How much time in between each prediction step.
VDeadzone	Deadzone for velocity. Current velocity will snap to target velocity when within the deadzone
ADeadzone	Deadzone for acceleration. Acceleration will snap to zero when within the deadzone

◆ VelocitySpringCharacterUpdate()

template<typename TVector >

static void SpringMath::VelocitySpringCharacterUpdate	(	TVector &	InOutPosition,
		TVector &	InOutVelocity,
		TVector &	InOutVelocityIntermediate,
		TVector &	InOutAcceleration,
		TVector	TargetVelocity,
		float	SmoothingTime,
		float	MaxAcceleration,
		float	DeltaTime,
		float	VDeadzone = `1e-2f`,
		float	ADeadzone = `1e-4f`
	)

inlinestatic

Update a position representing a character given a target velocity using a velocity spring. A velocity spring tracks an intermediate velocity which moves at a maximum acceleration linearly towards a target. This means unlike the "SpringCharacterUpdate", it will take longer to reach a target velocity that is further away from the current velocity.

Template Parameters

TVector The type of vector to use (e.g. FVector2D, FVector4, FVector etc)

Parameters

InOutPosition	The position of the character
InOutVelocity	The velocity of the character. Needs to be stored and persisted by the caller. Usually initialized to zero and not modified by the caller.
InOutVelocityIntermediate	The intermediate velocity of the character. Needs to be stored and persisted by the caller. Usually initialized to zero and not modified by the caller.
InOutAcceleration	The acceleration of the character. Needs to be stored and persisted by the caller. Usually initialized to zero and not modified by the caller.
TargetVelocity	The target velocity of the character.
SmoothingTime	The time over which to smooth velocity. It takes roughly the smoothing time in order for the character to reach the target velocity.
MaxAcceleration	Puts a limit on the maximum acceleration that the intermediate velocity can do each frame. If MaxAccel is very large, the behaviour wil lbe the same as SpringCharacterUpdate
DeltaTime	The delta time to tick the character
VDeadzone	Deadzone for velocity. Current velocity will snap to target velocity when within the deadzone
ADeadzone	Deadzone for acceleration. Acceleration will snap to zero when within the deadzone

◆ VelocitySpringDamper()

template<typename TVector >

static void SpringMath::VelocitySpringDamper	(	TVector &	InOutX,
		TVector &	InOutV,
		TVector &	InOutXi,
		TVector	TargetX,
		float	MaxSpeed,
		float	SmoothingTime,
		float	DeltaTime
	)

inlinestatic

A velocity spring will damp towards a target that follows a fixed linear target velocity, allowing control of the interpolation speed while still giving a smoothed behaviour. A SmoothingTime of 0 will give a linear interpolation between X and TargetX

Template Parameters

TVector The type of vector to use (e.g. FVector2D, FVector4, FVector etc)

Parameters

InOutX	The value to be damped
InOutV	The velocity of the value to be damped
InOutXi	The intermediate target of the value to be damped
TargetX	The target value of X to damp towards
MaxSpeed	The max velocity to use for the intermediate target interpolation
SmoothingTime	The smoothing time to use while damping towards X. Higher values will give more smoothed behaviour. A value of 0 will give a linear interpolation of X to Target
DeltaTime	The timestep in seconds

◆ VelocitySpringDamperF()

template<typename TFloat >

static void SpringMath::VelocitySpringDamperF	(	TFloat &	InOutX,
		TFloat &	InOutV,
		TFloat &	InOutXi,
		TFloat	TargetX,
		TFloat	MaxSpeed,
		float	SmoothingTime,
		float	DeltaTime
	)

inlinestatic

A velocity spring will damp towards a target that follows a fixed linear target velocity, allowing control of the interpolation speed while still giving a smoothed behavior. A SmoothingTime of 0 will give a linear interpolation between X and TargetX

Parameters

InOutX	The value to be damped
InOutV	The velocity of the value to be damped
InOutXi	The intermediate target of the value to be damped
TargetX	The target value of X to damp towards
MaxSpeed	The desired speed to achieve while damping towards X
SmoothingTime	The smoothing time to use while damping towards X. Higher values will give more smoothed behaviour. A value of 0 will give a linear interpolation of X to Target
DeltaTime	The timestep in seconds

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

Engine/Source/Runtime/Engine/Public/Animation/SpringMath.h

Static Public Member Functions

Member Function Documentation

◆ CriticalSpringDamper()

◆ CriticalSpringDamperAngle()

◆ CriticalSpringDamperQuat()

◆ CriticalSpringDamperQuatPredict()

◆ ExponentialSmoothingApproxAngle()

◆ ExponentialSmoothingApproxQuat()

◆ HalfLifeToSmoothingTime()

◆ SmoothingTimeToHalfLife()

◆ SmoothingTimeToStrength()

◆ SpringCharacterPredict()

◆ SpringCharacterUpdate()

◆ StrengthToSmoothingTime()

◆ VelocitySpringCharacterPredict()

◆ VelocitySpringCharacterUpdate()

◆ VelocitySpringDamper()

◆ VelocitySpringDamperF()