Participant

Regular • File: ParticipantTracking.csv • Writer: ParticipantObservationRecorder.cs via observer ParticipantTrackingObserver.cs

At a glance

Participant tracking captures the viewpoint pose (HMD or main camera) and the locomotion state (CharacterController-driven controller: position, rotation, velocity, grounded flag). Distinct from Body tracking, which captures the full skeletal pose — Participant is always the participant-vs-world state, regardless of whether a body skeleton is assigned.

Use Participant for:

• Head pose over time (gaze direction proxy, locomotion analysis).
• Controller velocity (locomotion speed, acceleration, pauses).
• Grounded-state transitions (jumps, falls, teleports).

When it writes

One row per LateUpdate, FixedUpdate, or both, depending on the Sampling Loop setting on the config SO. Optionally filtered:

• Distance / rotation threshold — only emit if the participant moved / rotated more than the configured minimum.
• Skip N — emit every Nth sample.

When the participant is stationary (within the threshold), no row is emitted — expect gaps in FrameNumber under those settings.

File & location

• Default: ParticipantTracking.csv in the run directory.
• Config SO: ParticipantTrackingDataCapture — assigned on the experience.

Configuration

ParticipantTrackingDataCapture SO fields:

Field	What it does
enabledLogging	Master enable/disable.
fileName	Override the default name. Default ParticipantTracking.csv.
flushEveryNRows	Batched flush cadence. Default 30.
writeHeader	Write the header row on first emission. Default true.
samplingLoop	Update / FixedUpdate / Both.
multipleSamplesPerFrame	If true, allow multiple samples within the same frame.
recordMode	Continuous (every sample) / MovementAndEvents (only when moving or on event boundaries) / EventsOnly.
emitEveryNSamples	Emit every Nth sample. Min 1, default 1.
positionThreshold	Minimum position change (metres) before MovementAndEvents emits. Default 0.01.
movementThreshold	Minimum rotation / movement magnitude before MovementAndEvents emits. Default 0.5.
cameraSource	Reference to the camera providing the viewpoint pose.
characterController	Reference to the locomotion CharacterController.
useEulerAngles	If true, rotation columns are Euler (X/Y/Z in degrees). If false, quaternion (X/Y/Z/W).

Columns

Shared prefix

See Column conventions — The shared prefix.

Domain columns

Column	Type	Units	Description
cameraPosX, cameraPosY, cameraPosZ	float	metres	Viewpoint position in environment coordinates.
cameraRotX, cameraRotY, cameraRotZ, cameraRotW	float	unit quaternion	Viewpoint rotation (quaternion mode).
cameraRotX, cameraRotY, cameraRotZ	float	degrees	Viewpoint rotation (Euler mode — no RotW).
controllerPosX, controllerPosY, controllerPosZ	float	metres	CharacterController position.
controllerRotX, controllerRotY, controllerRotZ, controllerRotW	float	unit quaternion / degrees	CharacterController rotation (quaternion or Euler, matching useEulerAngles).
controllerVelX, controllerVelY, controllerVelZ	float	m/s	CharacterController linear velocity in environment coordinates.
controllerIsGrounded	int	0 / 1	1 if the controller is grounded this frame, else 0.

Rotation column set depends on useEulerAngles. The column count differs (7 vs 6 per pose); always check the header line before hard-coding column indices.

Sample rows

Quaternion mode:

...shared...,cameraPosX,cameraPosY,cameraPosZ,cameraRotX,cameraRotY,cameraRotZ,cameraRotW,controllerPosX,controllerPosY,controllerPosZ,controllerRotX,controllerRotY,controllerRotZ,controllerRotW,controllerVelX,controllerVelY,controllerVelZ,controllerIsGrounded
...,0.0,1.72,-2.5,0.0,0.7071,0.0,0.7071,0.0,0.0,-2.5,0.0,0.7071,0.0,0.7071,0.0,0.0,0.0,1
...,0.03,1.72,-2.48,0.0,0.7071,0.0,0.7071,0.01,0.0,-2.49,0.0,0.7071,0.0,0.7071,1.2,0.0,0.8,1

Join with other streams

Standard FrameNumber join to ExperienceState:

import pandas as pd
exp = pd.read_csv("UpdateLoop.csv")
part = pd.read_csv("ParticipantTracking.csv")
joined = exp.merge(part, on="FrameNumber", how="left", suffixes=("_exp", "_part"))

Use how="left" rather than inner — if recordMode = MovementAndEvents or EventsOnly is set, Participant rows will not exist for every frame, and you want the full row set from UpdateLoop.csv with NaN controller values during stationary frames.

Gotchas

• Gaps when recordMode filters samples. With MovementAndEvents or EventsOnly, stationary frames produce no row. Don't assume every UpdateLoop.csv frame has a matching Participant row. Use left joins; forward-fill with pandas .ffill() if you need a dense series.
• useEulerAngles changes column count. Seven quaternion columns per pose become six Euler columns. Always read the header line rather than hard-coding indices.
• Quaternion sign ambiguity. q and -q are the same rotation. Numeric differences between rows don't equal angular distance. Convert via 2 * acos(|q1·q2|) or axis-angle before computing "how much did the head rotate."
• Camera vs. controller may differ. The viewpoint (HMD) moves with head motion; the CharacterController moves with locomotion input. In a seated experience they may be approximately equal; in roomscale they're not. Don't conflate.
• Velocity is engine-reported, not derived. controllerVelX/Y/Z comes from Unity's CharacterController, not from differencing positions. For head velocity you have to derive it yourself from successive cameraPos rows.

Analysis recipes

• Gaze paths — often combines camera pose from Participant with gaze direction from Eye.
• Cross-device sync — use MonotonicExecutionTime to align head-pose samples with external motion capture.