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> Unreal Engine API Reference > Runtime > Engine > GameFramework > FRootMotionSource

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FRootMotionSource

Generalized source of Root Motion to a CharacterMovementComponent.

Windows

MacOS

Linux

Inheritance Hierarchy

FRootMotionSource

	FRootMotionSource_ConstantForce
	FRootMotionSource_JumpForce
	FRootMotionSource_MoveToDynamicForce
	FRootMotionSource_MoveToForce
	FRootMotionSource_RadialForce

References

Module	Engine
Header	/Engine/Source/Runtime/Engine/Classes/GameFramework/RootMotionSource.h
Include	#include "GameFramework/RootMotionSource.h"

Syntax

struct FRootMotionSource

Remarks

Generalized source of Root Motion to a CharacterMovementComponent.

Has priorities and different accumulation modes (override, additive, set, ignore).

RootMotionSources are accumulated from highest priority to lowest, once all values are "finalized" (meaning no more accumulation to those values), root motion accumulation is finished. Having all of translation and rotation in a transform being overridden during root motion accumulation means that CharacterMovementComponent Phys*() functions no longer need to CalcVelocity() since it'll just get overridden anyway.

Some example source possibilities: Full Animation Root Motion (matching only form of root motion we've supported historically):

Overrides all translation axes or rotation or both
Very High priority so it gets applied first and since it is override no other RootMotionSources have an influence that are lower priority
Scale on translation and/or rotation is set to 1 to match animation 1 for 1
Provides local space transform (character-orientation relative)
End result: Same as before - overrides velocity/rotation to values in AnimMontage
But can now scale individual translation axes if desired, or instead of override can use "set" to allow other additive sources of root motion to be applied on top of the animation root motion (modify velocity to home root motion melee attacks, etc.)

Jump pad volumes that work during animation root montage attacks

Constant velocity modification Z up, additive and high priority
Attack/melee animation root motion uses "set" instead of "override" to allow other sources
Animation root motion is applied, then the Z up additive of this source is so you are affected by the jump pad

Attack/melee homing

Additive, lower priority so it gets applied after any animation/significant root motion
World space, sourced by logic modifying velocity to go towards nearby enemies
Could point to a UAbilityTask node from the GameplayAbilities system

Character movement controlled by splines/curves in-editor instead of requiring animation tweaks

Same as animation root motion but source from spline/curve data

Variables

	Name	Description
ERootMotionAccu...	AccumulateMode	Accumulation mode for this source (whether or not to additively apply this root motion or override completely)
bool	bInLocalSpace	True when this RootMotionSource is contributing local space accumulation (false for world space)
bool	bNeedsSimulatedCatchup	True when this RootMotionSource has been marked for simulated catchup - this Simulated version of the Source needs to catch up to where it was before being corrected by authoritative version.
float	CurrentTime	Time elapsed so far for this source
float	Duration	The length of this root motion - < 0 for infinite (to be removed manually)
FRootMotionFini...	FinishVelocityParams	Finish Velocity Parameters
FName	InstanceName	This name allows us to find the source later so that we can end it.
uint16	LocalID	ID local to this client or server instance.
float	PreviousTime	The last Time entry we had before the last SetTime() - used for simulated catchup
uint16	Priority	Priority of this source relative to other sources - higher number being the highest priority/first applied.
FRootMotionMove...	RootMotionParams	Root Motion generated by this Source
FRootMotionSour...	Settings	Settings of this source
float	StartTime	Time this source should start (in character movement client time) This is used to handle cases of inconsistent tick times (ServerMoves ticking for 1 second when root motion should have only applied for the last 0.1 seconds, or root motion source ending halfway through a 0.5 second tick)
FRootMotionSour...	Status	Status of this source

Constructors

	Name	Description
	FRootMotionSource()

Destructors

	Name	Description
	~FRootMotionSource()

Functions

	Name	Description
void	AddReferencedObjects ( FReferenceCollector& Collector )
void	CheckTimeOut()	Checks if this source has timed out and marks for removal if necessary
FRootMotionS...	Clone()
float	GetDuration()
UScriptStruc...	GetScriptStruct()
float	GetStartTime()
float	GetTime()
bool	IsActive()	True when this RootMotionSource should be affecting root motion
bool	IsStartTimeValid()
bool	IsTimeOutEnabled()
bool	Matches ( const FRootMotionSource* Other )	For well-networked RootMotionSources, any given FRootMotionSource child class could implement their own unique ID and simply use that in the Matches check.
bool	MatchesAndHasSameState ( const FRootMotionSource* Other )	Checks that it Matches() and has the same state (time, track position, etc.)
bool	NetSerialize ( FArchive& Ar, UPackageMap* Map, bool& bOutSuccess )
void	PrepareRootMotion ( float SimulationTime, float MovementTickTime, const ACharacter& Character, const UCharacterMovementComponent&... )	Generates the RootMotion for this Source, can be used for both "live" generation or for playback (client prediction correction, simulated proxies, etc.)
void	SetTime ( float NewTime )	Set the CurrentTime of this source.
FString	ToSimpleString()
bool	UpdateStateFrom ( const FRootMotionSource* Sourc..., bool bMarkForSimulatedCatchup )	Mainly for server correction purposes - update this Source's state from another's, usually the authoritative state from the server's version of the Source

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