Animation

Skeletal meshes, Animation Blueprints, State Machines, Blend Spaces, and IK in UE5.

📅 UE 5.4⏱ 25 min
UE5 Animation Blueprint state machine with Idle, Walk, Run, and Jump states
Animation Blueprint State Machine — states for Idle, Walk, Run, and Jump with transition rules driven by character speed and IsInAir.

Skeletal Mesh

A Skeletal Mesh is a 3D mesh bound to a hierarchical skeleton (a rig of bones). Each vertex is weighted to one or more bones; when bones transform, the mesh deforms accordingly. Import FBX or USD from Maya, Blender, or Motion Builder.

Assets created during import:

  • SK_ prefix — Skeletal Mesh asset
  • SKEL_ prefix — Skeleton asset (shareable across meshes)
  • PhysicsAsset — Ragdoll collision shapes per bone
  • AnimSequence — Individual animation clip

Animation Blueprint

The Animation Blueprint (AnimBP) drives which animations play on a Skeletal Mesh at runtime. It has two graphs:

  • Event Graph — Standard Blueprint logic. Reads gameplay state (speed, jumping, health) into variables each frame.
  • Anim Graph — Pose graph. Evaluates animation nodes and outputs a final bone pose. This is where blending happens.

State Machines

A State Machine node in the Anim Graph defines discrete animation states (Idle, Walk, Run, Jump, Fall, Land) and transitions between them, each governed by a Boolean rule expression.

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Transition Rules

Keep transition rules simple — read pre-computed variables from the Event Graph rather than calling functions inside transition conditions. This avoids evaluation overhead.

Blend Spaces

A Blend Space smoothly interpolates between multiple animation clips across a 1D or 2D axis. A common setup:

  • X axis — Speed (0 → 600 cm/s)
  • Y axis — Direction (-180° → 180°)
  • Sample points — Idle at (0,0), Walk forward at (200,0), Run at (600,0), Walk backward at (200,180)

At runtime, pass Speed and Direction variables; UE5 automatically triangulates between samples.

UE5 1D Blend Space showing interpolation between Idle, Walk, and Run
1D Blend Space with Idle → Walk → Run clips sampled at speed values 0, 200, and 600 cm/s.

Inverse Kinematics (IK)

UE5 provides several IK solvers in the Anim Graph:

  • Two Bone IK — Solves a two-joint chain (arm, leg) to reach a target position. Classic foot IK.
  • FABRIK — Forward And Backward Reaching IK. Solves chains of any length.
  • Full Body IK (FBIK) — Rig Control-based multi-chain solver. Used for realistic full-body poses.
  • Control Rig IK — Powerful procedural rig system with its own node graph. Enables foot planting, spine leaning, and look-at behaviors.

Motion Warping

Motion Warping adjusts root-motion animations at runtime to hit a specific target location or rotation. Add a UMotionWarpingComponent to your character and place Warp Windows in Animation Sequences via notifies. No re-animation required — the system deforms the trajectory in-place.