Tiny rotational discrepancies expand the walkable range
Aliases: curvature gain · rotation gain · RDW
What it is
The user believes they are walking a straight line through a hall; the physical trajectory is a gentle arc toward the centre of the empty floor. Redirected walking injects a rotational or translational discrepancy, just below notice, between virtual heading and physical heading, so a limited floor can be remapped onto a larger virtual path. What expands is walkable virtual range, not the walls.
It depends on “the discrepancy is small and the person is still walking by eye,” not on making them spin. Going above threshold, and not having enough space, are separate claims.
Why it happens
When vision dominates spatial updating, heading follows the virtual world rather than the arc under the feet. Three gains are common: curvature gain bends a virtual straight into a physical arc, rotation gain multiplies or shrinks the virtual world during a real turn, translation gain makes a physical step longer or shorter virtually. If the discrepancy stays inside visual recalibration, the bent physical path is experienced as straight, and the same patch of floor can be reused.
Redirection works inside the walking channel. It does not delete optic flow and does not turn translation into a jump, so path integration and comfort still book as walking. The algorithm has to predict the next few seconds of path to bend the person toward empty floor rather than toward a coffee table; a wrong prediction forces an overt reset (a virtual turn, a stop), and that reset is usually noticeable.
Studying it
In an empty patch of known size, have people walk a virtual straight or polyline, and compare physical trajectories with and without gain. Success is: the virtual path is completed, no pad is hit, and people afterwards report whether they felt themselves turning. Manipulate gain type and amount; record physical curvature, minimum distance to a wall, and whether a reset was required.
Pointing at “where the virtual origin is” checks that spatial updating followed vision. If pointing follows the physical room, redirection failed in the spatial representation even if nobody hit a wall.
Where it stops holding
Once people look at their feet, touch a real wall, or take the real room as reference (furniture seen through passthrough), visual dominance breaks and the arc shows. Seated use and walking-in-place do not give curvature gain enough gait to work with. Scenes with little optic flow (darkness, fog, almost no texture) cannot carry heading. In a furniture slot the algorithm resets often; the experience becomes “the system twisted me,” not an unnoticed expansion. Redirection does not replace a safety boundary: it expands a mapping, it does not remove real obstacles from the room.
Applying it
- Enable curvature redirection only when people are primarily walking and the scene has enough ground texture and flow. Turn it off in menus and near-field work.
- Use gain to bend people toward the empty centre. Do not use it to force a virtual straight through furniture.
- Make resets explicit (a stop, a virtual-turn prompt). Do not yaw the view mid-stride.
- How to check: in a cleared room of known size, walk a virtual straight longer than the room. The physical path should be an arc toward centre, people should report a straight walk, and no reset should fire. Fail any of the three and the technique is not yet expanding range.