Animation II: Animation Blueprints Project 2 due · crit

Mon 2:00 · Brief How Unreal turns clips into behavior

A clip is raw motion; the Animation Blueprint is the logic that decides which motion plays, when, and how it blends.

The AnimGraph, states, and variables

An Animation Blueprint (Anim BP) evaluates a pose every frame in its AnimGraph. Inside it, a State Machine holds states that each play a clip (or a Blend Space). Transitions connect states and fire when their transition rules — tested against variables — are true. You update those variables in Event Blueprint Update Animation, reading from the owning pawn. Your gameplay Blueprint never touches clips directly; it drives values like Speed or IsJumping, and the Anim BP resolves what plays. That separation is the whole point: motion authoring and game logic stay decoupled.

Blend Spaces

Hard transitions between Idle, Walk, and Run look terrible. A Blend Space is a single asset that mixes several clips along one or two axes — feed it Speed and it cross-fades idle → walk → run continuously as the value climbs. One float now drives your entire locomotion range with no visible seams, and you plug the Blend Space straight into the AnimGraph.

Retargeting and root motion

Unreal's IK Retargeter maps animation from a source Skeleton onto your target Skeleton, so a clip authored on one body plays on another — that's how a Mixamo animation lands on your student Skeleton. Root motion means the clip moves the character through the world; in-place means the clip animates the legs while the Character Movement Component moves the capsule. Games usually key locomotion in-place and drive position from movement, reserving root motion for authored moments like a mocap attack or a scripted vault.

Mon 2:45 · Guided lab Build the Animation Blueprint

In Unreal Engine 5.8, with your Skeleton and your three clips imported — we move fast, Project 2 is due today.

1. Import onto your Skeleton

   Import your FBX clips and, when prompted, target your character's existing Skeleton asset rather than creating a new one. Confirm each clip previews cleanly on the Skeleton before moving on.

2. Create the Anim BP and Blend Space

   Create an Animation Blueprint targeting your Skeleton. Author a 1D Blend Space with a Speed axis, dropping idle/walk/run onto the samples so it cross-fades cleanly across the range.

3. Build the State Machine

   In the AnimGraph, add a State Machine and drop in Idle, Walk/Run (your Blend Space), and any action states. Connect the state machine's output pose to the Output Pose node. Set Idle as the entry state.

4. Wire transitions with rules

   Connect the states and give each transition a rule tested against Speed (and other variables). Tune blend duration on each transition so it feels snappy, not mushy, and keep locomotion responsive to input.

5. Set variables in Event Graph

   In Event Blueprint Update Animation, get the owning pawn, read its velocity, and set your Speed variable each frame. The AnimGraph reads those variables — never the other way around.

6. Retarget a Mixamo clip

   Download a Mixamo clip and use the IK Retargeter to retarget it from the Mixamo source Skeleton onto your student Skeleton. Bake out the retargeted clip, then wire it to a new state — check for finger and hip drift and refine the retarget chains.

7. Drive from the pawn

   In your Character Blueprint, read Enhanced Input and feed movement into the Character Movement Component; the Anim BP's Update event picks up the resulting velocity. No manual clip playback needed — the graph resolves the pose.

8. Test in PIE

   Hit Play In Editor, open the Anim BP debugger to watch the active state light up, and confirm locomotion blends and the retargeted action fire. Fix any hitching before crit.

Wed 2:00 · Agent lab Let it wire, then you trace

Keep this tight — Project 2 is due. The agent scaffolds; you own every transition and node it draws.

Wed 3:10 · Crit / share Project 2 — Rigged & Animated Character

Project 2 is due today and goes to crit in engine. Each character plays live in PIE: we watch deformation as it moves and judge clip quality — does the walk carry weight, does the run read, does the action land, and do the Anim BP blends hold up under changing input? Be ready to show the AnimGraph and State Machine and speak to your root-motion choice. In-engine playback only; no rendered videos.

Homework — due before Week 10

Resources

• Animation Blueprints — the AnimGraph, State Machines, and variables, top to bottom.
• Blend Spaces — mixing locomotion clips along one or two axes.
• IK Retargeter — how a Mixamo clip plays on your Skeleton via retargeting.
• Mixamo — sourcing and downloading clips to retarget.