Head-Directed Target Locking

1. Overview

Pattern Level: Sub-pattern of Audio-First Dual-Mode Navigation
Primary Phase: Guiding
One-line Summary: A target selection mechanism that locks onto a navigation target when the player maintains head orientation toward it for a short period, suppressing cues from other characters and playing a sequential audio preview.
Source: Voices of the Boyne (Battle of Boyne, Hill of Tara, National Botanic Garden)

Name

• Head-Directed Target Locking

Intent

To give players a way to choose which character to navigate toward using head orientation as the input, without any screen interaction. It also allows players to briefly orient toward a distant character to get a rough sense of its direction, helping them build a mental map of the site while continuing toward their current destination.

2. Target

Problem

In a visual game, choosing a navigation target is straightforward. In an audio-only experience with multiple active characters, the player receives cues from several directions at once. Without a selection mechanism, there is no way to focus on one character or tell the system which one to find. The soundscape becomes difficult to interpret and navigation feels unreliable. Confirming selection through sound alone, without a map or radar, is genuinely harder to achieve than in visual games.

Context

• Multiple characters are active and emitting navigation cues in Wander mode.
• IMU-based head tracking is providing continuous heading data.
• Players are navigating on foot and may be turning their heads naturally as they walk.
• No visual map or target indicator is available.

Use When

• One or more characters are within navigation range simultaneously.
• A player has been facing a particular direction long enough to suggest intentional orientation.
• The system needs to prioritise one character’s cues over others.
• A player turns away from a locked target, suggesting they want to change direction.

Forces

• Selection confidence vs. accidental triggering: dwell time must distinguish intentional orientation from natural head movement, but be short enough to feel responsive.
• Lock persistence vs. flexibility: once locked, the player needs confidence the system is committed, but breaking the lock should require only a natural head turn.
• Angular precision vs. usability: a narrow lock angle is precise but frustrating at long range where GPS and IMU error combine. A wider angle is more forgiving but reduces the feeling of intentional aim.
• Audio suppression vs. site awareness: suppressing other cues during a lock helps focus, but the player temporarily loses awareness of where other characters are.

Consequences

Weaknesses:

• If the IMU sensor disconnects, the system falls back to phone sensors requiring the phone to be held upright. A phone left in a pocket will produce incorrect heading data.
• Players unfamiliar with dwell-time selection may turn toward a sound and immediately turn away, never triggering the lock.
• Lock angle thresholds need tuning per site. Dense sites need a narrower angle to avoid locking onto the wrong character.
• Suppressing other cues during a lock reduces site awareness.

Strengths:

• Target selection feels like a natural extension of listening. No separate selection interface is needed.
• The sequential preview builds anticipation and confirms lock without visual feedback.
• Passive orientation during the Potential state lets players survey the site through audio alone.
• Auto-switch prevents navigation dead ends in sites with closely spaced characters.

3. Application

Solution

1. None — no target selected. All eligible characters take turns emitting a single cue in rotation.
2. Potential — the player’s heading is within the lock angle threshold of a character. A timer begins. No audio change yet.
3. Locked — the player holds their heading within the threshold for the full dwell period. The locked character’s cues play in sequence. Other characters’ cues are suppressed. A brief lock confirmation sound plays.
4. Lock release — the player’s heading moves beyond the break angle. A brief unlock sound plays. The system returns to None. Standard cycling resumes after a short pause.
5. Auto-switch — if a closer character enters the lock angle while the player is locked onto a more distant one, the system switches to the nearer character. A new lock sound plays.

Rationale

• Dwell-time selection prevents accidental locks from natural head turns while walking.
• The sequential preview rewards commitment to a direction and signals that the system has responded to the player’s intent.
• Auto-switching to closer characters prevents a player walking past a nearby character because they were locked onto a more distant one.
• The Potential state lets players survey the site by slowly turning their head and hearing each character’s cue, partially compensating for the absence of a visual map.

Design Parameters

Example

Two characters are active. The player turns to face a sound from the northeast and holds that orientation. After half a second a chime confirms the lock. The other character goes silent. The locked character plays its cues in sequence, giving a preview of the full theme. The player walks northeast. Twenty metres later the cues shift slightly eastward. The player adjusts course. The cues end and the character’s music begins, marking the end of Wander mode.

Implementation Notes

• Heading comparison must correctly handle the wraparound between 0 and 360 degrees. Standard arithmetic subtraction will give incorrect results near north.
• The comparison should use the smallest angular difference between the player’s heading and the bearing to a target, not their raw difference.
• Provider priority should favour a dedicated IMU sensor over the phone compass when both are available. The phone compass is affected by nearby metal objects and electrical interference outdoors.
• Brief heading deviations under 0.5 seconds during a lock should not break it. Normal head movement while walking should not repeatedly unlock and relock the target.
• Lock state must be cleared completely on Interact mode entry: targeting state, sequential cue index, and all timers.

Evidence / Source

• Deployed at Battle of Boyne heritage site with 25 participants.
• Players naturally discovered the turn-and-hold mechanic through the tutorial without needing to read instructions.
• Current field testing is evaluating a wider lock angle of 37.5 degrees to improve comfort while walking.

Composition Recipes

Recipe	Scenario	Guiding	Indicating	Presenting + Notes
R1	Multi-character navigation	Directional Audio Navigation Cues cycling across all targets	Head-Directed Target Locking selects one character, sequential preview begins	Progressive Proximity Audio Zones take over when the locked character is reached
R2	Passive site survey	Player turns slowly to orient toward each character in Potential state	Head-Directed Target Locking Potential state gives cue feedback per direction without committing	Player builds a mental map of the site through audio, then locks onto preferred target
R3	Dense site navigation	Directional Audio Navigation Cues with narrow lock angle	Head-Directed Target Locking with site-tuned angles to avoid locking onto wrong character	Progressive Proximity Audio Zones on arrival