While moving, overlay density should drop to leave attention for the environment

What it is

Standing, an assembly drawing may be dense; the moment a foot goes out, the same drawing is competing for attention that belonged to the floor and to people. Locomotion-triggered density reduction cuts on motion state: walking, turning, going up or down a step, overlays drop to a minimum and expand again only when still. What is yielded is not aesthetic empty space. It is avoidance bandwidth.

This is not “the environment is already full, so draw less,” and not a task-step switch. The trigger is whether the body is moving.

Why it happens

Walking is itself a continuous perception–action loop: optic flow, footfall, others’ trajectories. Overlay reading interrupts or inserts into that loop. Faster, more irregular ground, more of the loop is occupied, less remainder for the layer. A density that tested “acceptable” while standing becomes a missed step while walking. Reduction admits that motion rewrites the attention budget, rather than making the user close a menu while they walk.

The cut should enter low density before the first step, not fade after two metres. Late, and they are already walking on a standing quota. Return needs hysteresis: fill the moment they stop, and they are covered before they are planted. A few seconds of hysteresis, or an explicit “expand,” is safer than an automatic snap-back.

Studying it

Walk–stop alternation: the same overlay kit, comparing no change while moving, auto-drop to a navigation arrow, and clear while moving. The path includes turns and slight level changes. Record missed steps, furniture hits, reaction to environment events, and whether re-expanding after a stop causes a second occlusion.

Motion factors: pace, head turn or not, path complexity. Density policy: threshold (pace / head motion), how far it drops, return hysteresis. Safety scores: missed footfalls, collisions, missed approachers; efficiency: time to resume the task after stopping.

Treadmill walking and free walking differ in head stability and avoidance demand. Do not conclude from a treadmill alone.

Where it stops holding

Seated motion (wheelchair, vehicle passenger) is mostly visual flow, not a leg loop; thresholds must be marked separately, not copied from walking speed. A head-only turn to reach something distant should not clear the whole layer, or precise placement is collateral damage; drop the large central panel and keep pointing. Emergency navigation (an exit in smoke) still needs one high-contrast heading while moving; reduction is not reduction to zero. “Walking” in a factory may be sidestepping with occupied hands; a manual close is not available. People who have long relied on arrows will panic more after a drop — that is scanning atrophy, another issue. The drop still has to happen, while keeping minimum environment visibility.

Applying it

• Trigger on pace or waist translation: above standing micro-motion, enter a walking tier with only a heading or one word for the next step; return to a work tier only below threshold and stable for seconds.
• The walking tier forbids solid large panels and paragraphs that must be read. To look at a drawing, stop. Do not read while walking.
• Give return a visible transition so the layer does not snap into the centre on the same frame they plant.
• How to check: walk from the bench to the door and back, with a carton on the way. In the walking tier the layer should already be thin, and the carton yielded to before contact. Still reading an assembly paragraph while walking, and hitting the carton, means the trigger is still on the standing quota.

Related

• Same group：N5.13.1 An overlay hiding a dynamic hazard in the real environment is the highest-grade risk · N5.13.3 On a performance crash or see-through failure, fallback must prioritize environment visibility · N5.13.4 Stairs, crossings and other safety-critical zones need a rule that clears or fades overlays · N5.13.5 Long-term reliance on overlay cues weakens active scanning of the real environment
• Nearby：N5.07 Overlay Density · N5.12 Overlay Density in Real-world Context
• Search terms：locomotion-triggered density · walking HUD · mobility and attention