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.