UKismetAnimationLibrary::K2_CalculateVelocityFromSockets
#include "KismetAnimationLibrary.h"
Access: public
Specifiers: staticUFUNCTIONBlueprintCallable
Description
Tracks the motion of an offset position on a bone/socket over time — optionally relative to another bone/socket as a moving reference frame — and returns a smoothed, optionally eased velocity magnitude. Used for things like measuring a hand's velocity relative to the pelvis.
Caveats & Gotchas
- • Marked NotBlueprintThreadSafe — cannot run inside multithreaded Anim Graph evaluation, unlike most of this library.
- • History must be a persistent variable across calls, exactly like K2_CalculateVelocityFromPositionHistory — passing a fresh FPositionHistory each call breaks the velocity computation.
- • ReferenceSocketOrBone lets the tracked position move with a parent bone (e.g. tracking a hand relative to the pelvis instead of the world) — set it to None to track in the given SocketSpace directly instead.
- • CustomCurve is only read when EasingType is set to the Custom easing type; otherwise it's ignored.
Signature
static float K2_CalculateVelocityFromSockets(float DeltaSeconds, USkeletalMeshComponent * Component, const FName SocketOrBoneName, const FName ReferenceSocketOrBone, ERelativeTransformSpace SocketSpace, FVector OffsetInBoneSpace, UPARAM(ref) FPositionHistory& History, int32 NumberOfSamples, float VelocityMin, float VelocityMax, EEasingFuncType EasingType, const FRuntimeFloatCurve& CustomCurve)Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| DeltaSeconds | float | Time passed in seconds since the last call. | — |
| Component | USkeletalMeshComponent* | The skeletal component to look up the bone/socket within. | — |
| SocketOrBoneName | const FName | Name of the bone/socket to track over time. | — |
| ReferenceSocketOrBone | const FName | Bone/socket to use as a frame of reference, or None for world space. | — |
| SocketSpace | ERelativeTransformSpace | The transform space used to evaluate the tracked socket/bone. | — |
| OffsetInBoneSpace | FVector | Relative position offset, in the space of the tracked bone/socket, to track over time. | — |
| History | FPositionHistory& | Persistent storage for the position history; must be a variable that stays alive between calls. | — |
| NumberOfSamples | int32 | Number of samples to retain for the history — higher values smooth the velocity result more. | 16 |
| VelocityMin | float | Minimum velocity for normalization; if both min and max are 0, normalization is disabled. | 0.f |
| VelocityMax | float | Maximum velocity for normalization; if both min and max are 0, normalization is disabled. | 128.f |
| EasingType | EEasingFuncType | Easing function applied when normalizing the velocity result. | — |
| CustomCurve | const FRuntimeFloatCurve& | Curve asset used when EasingType is set to Custom. | — |
Return Type
float Example
Track hand velocity relative to the pelvis C++
// FPositionHistory HandVelocityHistory; // member variable, persists across ticks
const float HandSpeed = UKismetAnimationLibrary::K2_CalculateVelocityFromSockets(
DeltaSeconds, SkeletalMeshComp, TEXT("hand_r"), TEXT("pelvis"),
ERelativeTransformSpace::RTS_World, FVector::ZeroVector,
HandVelocityHistory, 16, 0.0f, 128.0f, EEasingFuncType::Linear, FRuntimeFloatCurve());Tags
Version History
Introduced in: 4.0
| Version | Status | Notes |
|---|---|---|
| 5.6 | stable | — |
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