pie-studio

PIE record, replay, observe, and input injection for ue-mcp.

Install

ue-mcp plugin install pie-studio

This installs the npm package, deploys the native C++ module to your project's Plugins/ directory, and adds the plugin to your ue-mcp.yml. Rebuild the UE project before launching the editor.

Editor UI

PIE Studio adds a toolbar button group to the UE5 editor (next to the Play controls) and a dockable panel accessible from the three-dot dropdown or Tools > PIE Studio.

Toolbar

Button	Action
Record (arm)	Arms the input recorder — waits for PIE to start, then captures all input
Record + Play	Arms the recorder and immediately starts PIE
Three-dot menu	Contextual options: arm, disarm, stop, open panel

Panel Sections

Recorder — status display showing current state, recording ID, frame count, and elapsed time.

Time Scale — slider and quick-set buttons (1%, 10%, 25%, 50%, 100%, 200%) to control PIE playback speed. Persists across PIE restarts.

Recordings — lists all saved recordings with:

• Play button to replay (arms replayer + active observation profiles, starts PIE, captures viewport frames, generates GIF)
• Delete button
• Collapsible GIF list per recording with Open (launches in default viewer) and Delete

Observation Profiles — manages UMCPObservationProfile data assets:

• Checkbox toggles to mark profiles as active
• Active profiles automatically observe during replay
• Create, Edit (opens UE asset editor), Delete, Refresh
• Multiple profiles run simultaneously, each producing independent output

Observation Profiles

Observation profiles are UDataAssets that control what gets sampled during replay. Create them from the panel or the Content Browser.

Field	Description
Tracked Values	Gameplay properties to observe (e.g. CharacterMovement.Velocity.X). Each can override the drift threshold.
Tracked Actors	Actors to track by ID — position, rotation, velocity sampled each frame.
Capture Pawn State	Sample pawn transform, velocity, movement state each frame.
Capture Montage	Sample active anim montage name and position.
Drift Thresholds	Minimum change to count as divergence. Filters physics/animation jitter. Position (cm), Rotation (deg), Velocity (cm/s), and a default for tracked values.

GIF Capture

Every replay automatically captures viewport frames and encodes an animated GIF (no external dependencies — built-in LZW encoder). GIFs are saved to <recording>/captures/replay_<timestamp>.gif, scaled to max 720px wide.

MCP Actions

33 actions in the pie category (provisioned by the plugin; call as pie(action="...")):

• Recording — record_arm, record_disarm, record_stop, record_status, record_list, record_read, record_delete, mark
• Replay — replay_arm, replay_disarm, replay_stop, replay_status with drift tracking and viewport capture
• Observation — observe_arm, observe_disarm, observe_stop, observe_status, observe_list, observe_read with profile-based sampling
• Input injection — inject_input, inject_input_start, inject_input_update, inject_input_stop, inject_input_tape
• Profiles — profile_create, profile_read, profile_update, profile_delete, profile_list
• Diff / Snapshot — record_diff, snapshot
• PIE inspection — anim_state, anim_properties, subsystem_state

Data Layout

<Project>/Saved/MCPRecordings/
  <recording-id>/
    manifest.json        # recording metadata
    sequence.json        # input sequence
    recording.csv        # frame-by-frame state
    drift.json           # replay drift report
    captures/
      replay_20260527_171430.gif
      replay_20260527_183200.gif

<Project>/Saved/MCPObservations/
  obs_<profile>_<timestamp>/
    manifest.json
    observation.csv
    tracked.jsonl

Develop

npm install
npm run build

See ue-mcp plugin docs for the full author contract.