Animate skeletal meshes in Unreal using the AnimInstance / Animation Blueprint model — C++ UAnimInstance base class (NativeInitializeAnimation, NativeUpdateAnimation, NativeThreadSafeUpdateAnimation), AnimGraph with state machines and blend spaces, animation assets (UAnimSequence, UBlendSpace, UAnimMontage, UAnimComposite, UPoseAsset), anim notifies and notify states, montage playback and delegates, linked anim layers, Motion Matching (Pose Search plugin), and Motion Warping. Use when setting up character animation, driving locomotion blends from C++, playing montages for actions, firing gameplay events at precise animation frames (notifies), switching animation sets at runtime, or integrating the Pose Search / Motion Warping plugins.
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Animate skeletal meshes in Unreal using the AnimInstance / Animation Blueprint model — C++ UAnimInstance base class (NativeInitializeAnimation, NativeUpdateAnimation, NativeThreadSafeUpdateAnimation), AnimGraph with state machines and blend spaces, animation assets (UAnimSequence, UBlendSpace, UAnimMontage, UAnimComposite, UPoseAsset), anim notifies and notify states, montage playback and delegates, linked anim layers, Motion Matching (Pose Search plugin), and Motion Warping. Use when setting up character animation, driving locomotion blends from C++, playing montages for actions, firing gameplay events at precise animation frames (notifies), switching animation sets at runtime, or integrating the Pose Search / Motion Warping plugins.
metadata
{"engine-version":"5.8","category":"animation"}
Animation system
A USkeletalMeshComponent is animated by a UAnimInstance — the runtime behind an
Animation Blueprint. The recommended architecture is a C++ UAnimInstance base that
computes animation variables each frame, with the AnimBP's AnimGraph consuming those
variables to produce the final pose.
When to use this skill
Setting up a character's locomotion (idle, walk, run, jump) with state machines and blend
spaces driven from C++.
Playing one-off animations (attacks, reloads, hit reactions) via montages with section
control and completion delegates.
Firing gameplay events (footsteps, hit windows, VFX triggers) at precise animation frames
using custom anim notifies.
Switching animation sets at runtime with linked anim layers / LinkAnimClassLayers.
Integrating the Pose Search (Motion Matching) or Motion Warping plugins.
Heavy per-frame logic (read-only, no world queries)
The AnimGraph evaluates the pose (state machines → blend spaces → IK → final pose). It
runs on the anim worker thread and must only read data the game thread wrote.
The C++ update path computes the variables the graph reads — never drive the final
bone transform directly from game code.
// MyAnimInstance.cpp#include"MyAnimInstance.h"#include"GameFramework/Character.h"#include"GameFramework/CharacterMovementComponent.h"#include"KismetAnimationLibrary.h"// CalculateDirectionvoidUMyAnimInstance::NativeInitializeAnimation(){
Super::NativeInitializeAnimation();
OwnerCharacter = Cast<ACharacter>(TryGetPawnOwner()); // cache once; safe on game thread
}
voidUMyAnimInstance::NativeUpdateAnimation(float DeltaSeconds){
Super::NativeUpdateAnimation(DeltaSeconds);
// Keep lightweight — prefer NativeThreadSafeUpdateAnimation for heavy logicif (!OwnerCharacter) { OwnerCharacter = Cast<ACharacter>(TryGetPawnOwner()); }
}
voidUMyAnimInstance::NativeThreadSafeUpdateAnimation(float DeltaSeconds){
Super::NativeThreadSafeUpdateAnimation(DeltaSeconds);
if (!OwnerCharacter) { return; }
const FVector Vel = OwnerCharacter->GetVelocity();
Speed = Vel.Size2D();
bIsFalling = OwnerCharacter->GetCharacterMovement()->IsFalling();
Direction = UKismetAnimationLibrary::CalculateDirection(Vel, OwnerCharacter->GetActorRotation());
}
Key rules:
NativeInitializeAnimation — cache owner/movement references; runs once on game thread.
NativeUpdateAnimation — game-thread update; keep minimal; call Super first.
NativeThreadSafeUpdateAnimation — worker-thread update; no UWorld queries, no spawning,
no non-thread-safe engine calls. This is where to put heavy per-frame computation.
Assign variables used by the AnimGraph as UPROPERTY(BlueprintReadOnly) — the AnimGraph
nodes read them by name. BlueprintThreadSafe meta is needed if accessed in thread-safe
graph functions.
Assign at runtime:
GetMesh()->SetAnimInstanceClass(MyAnimBPClass); // TSubclassOf<UAnimInstance>
UMyAnimInstance* AI = Cast<UMyAnimInstance>(GetMesh()->GetAnimInstance());
Animation assets
Asset
Class
Use
Animation Sequence
UAnimSequence
Single clip bound to a skeleton
Blend Space (2D)
UBlendSpace
Blend clips by two parameters (speed × direction)
Blend Space 1D
UBlendSpace1D
Blend clips by one parameter (speed)
Aim Offset
UAimOffsetBlendSpace
Additive aim-offset by pitch/yaw
Montage
UAnimMontage
Sectioned one-off animations with slot blending
Composite
UAnimComposite
Stitch sequences into one timeline
Pose Asset
UPoseAsset
Curve-driven morph targets / facial poses
All assets target a USkeleton — clips are shareable across meshes that use the same
skeleton (or compatible skeletons; see USkeleton::CompatibleSkeletons).
State machines
State machines in the AnimGraph define locomotion or combat states. Each state holds an
animation graph sub-network; transitions carry rule expressions.
From C++, query state machine state via FAnimNode_StateMachine:
GetCurrentStateName() — FName of the active state.
GetStateWeight(int32 StateIndex) — blend weight of a state during transition.
Prefer driving transitions through UPROPERTY variables computed in the C++ update rather
than calling native state machine APIs directly.
Montages (actions on top of locomotion)
Montages play in a named slot the AnimGraph exposes. The slot node blends the montage
over the base locomotion pose — good for attacks, reloads, hit reactions:
UAnimInstance* AI = GetMesh()->GetAnimInstance();
// Play and get the length (or set ReturnValueType to MontageLength / Duration)float Len = AI->Montage_Play(AttackMontage, 1.f);
// Jump to / stop sections
AI->Montage_JumpToSection(FName("Combo2"), AttackMontage);
AI->Montage_Stop(0.2f, AttackMontage);
// ACharacter convenience wrappersPlayAnimMontage(AttackMontage, 1.f, FName("Intro"));
StopAnimMontage(AttackMontage);
Bind to completion to know when an action finishes:
Notifies are the correct way to synchronize gameplay to animation timing. Using timers as a
substitute diverges at variable play rates and when animation blending delays the clip.
Linked anim layers (runtime animation set swapping)
Linked anim layers let you swap a portion of the AnimGraph at runtime — useful for weapon
styles, character class variations, or costume-specific animations:
// Replace the locomotion layer at runtimeGetMesh()->LinkAnimClassLayers(URifleLocomotionLayer::StaticClass());
// Revert to the default layer defined in the AnimBPGetMesh()->UnlinkAnimClassLayers(URifleLocomotionLayer::StaticClass());
// Retrieve the active layer instance to set variables on it
UAnimInstance* Layer = GetMesh()->GetLinkedAnimLayerInstanceByClass(URifleLocomotionLayer::StaticClass());
The linked AnimBP class must implement the same UAnimLayerInterface interface as the parent.
Modern options (5.x)
Motion Matching (PoseSearch plugin) — data-driven locomotion selects poses from a
database matching trajectory and pose queries. Replaces hand-built state machines for
complex locomotion. Enable PoseSearch in the project plugins.
Motion Warping (MotionWarping plugin) — warps root-motion clips to hit target
positions/rotations at runtime (ledge grabs, cover transitions). Add
UMotionWarpingComponent to the character; annotate montages with warp windows;
call AddOrUpdateWarpTargetFromTransform before playing.
Control Rig in the AnimGraph — procedural bone adjustments, IK, foot planting
(see control-rig-and-ik).
Layered blend per bone (FAnimNode_LayeredBoneBlend) — blend an upper-body montage
slot over a lower-body locomotion pose, or blend full-body layers with per-bone masks.
Inertialization (AnimNode_Inertialization) — cost-efficient smooth blending by
recording velocity rather than maintaining two full pose evaluations simultaneously.
Animation Sharing plugin — share a single AnimInstance across multiple distant characters
to reduce per-character animation cost.
Gotchas
Non-thread-safe calls in NativeThreadSafeUpdateAnimation — any call that touches the
UWorld, spawns objects, or reads non-thread-safe data will crash under multi-threaded anim
update. Cache all needed references in NativeInitializeAnimation.
Wrong skeleton — clips won't apply; retarget with the IK Retargeter or add the mesh's
skeleton to USkeleton::CompatibleSkeletons.
Driving the pose from game code instead of the AnimGraph — fighting the animation
system. Compute data in C++; let the graph own the pose.
Using timers for animation-timed events instead of notifies — desync at variable play
rates and when blending delays a clip's effective start.
Forgetting to call Super in NativeUpdateAnimation / NativeInitializeAnimation —
the engine does essential bookkeeping in the base implementation.
Heavy game-thread logic in NativeUpdateAnimation for many characters — move it to
NativeThreadSafeUpdateAnimation to run in parallel across characters.
Slot with no weight in the AnimGraph — montage plays but produces no output; ensure
the slot node is wired between source and output and the blend weight is > 0.
bUseMultiThreadedAnimationUpdate disabled on the AnimBP — disables the worker-thread
path; re-enable (default on) unless you deliberately need single-threaded evaluation.
Version notes
TObjectPtr<T> is the modern member UPROPERTY form (UE5+); older code uses raw T*.
NativeThreadSafeUpdateAnimation was introduced in UE 4.15 and is stable across all
UE 5.x versions.
LinkAnimClassLayers / UnlinkAnimClassLayers replaced the deprecated SetLayerOverlay /
ClearLayerOverlay (deprecated since 4.24).
SetAnimInstanceClass (the USkeletalMeshComponent overriding version) deprecated
K2_SetAnimInstanceClass (deprecated 4.23) and a TSubclassOf setter (deprecated 5.5).
The PoseSearch plugin (Motion Matching) is production-ready in UE 5.4+ and ships with
the engine (no separate download). API surface stabilized significantly in 5.4.
