Locomotion, Scale & Comfort

The root of nearly all VR discomfort is a single mismatch. Your vestibular system - the balance sensors in your inner ear - senses real acceleration and motion. Your eyes report what you see. When you physically walk, the two agree, and you feel fine. But when the virtual view glides you forward while your body sits still, your eyes say you are moving and your inner ear says you are not. Your brain, evolved to read that conflict as poisoning, responds with the classic symptoms: cold sweat, headache, nausea. This is VR sickness (also called simulator sickness), and it is the single biggest reason a design review ends early.

This is why locomotion design is not a convenience question but a comfort question. The two levers you have are how movement happens (teleport avoids the conflict; smooth movement creates it and must be softened) and how steady the experience is (the ~90fps and low latency from lesson 8.1 - because dropped frames and lag amplify sickness dramatically). A stuttering scene makes even good locomotion nauseating, which is why performance and comfort are the same subject seen from two sides.

The reassuring truth is that comfort is largely solvable with known techniques, and different people have very different tolerances. A seasoned developer may be happy with full smooth locomotion; a first-time client is not. Design for the least experienced person who will wear the headset - which, in architectural review, is almost always the client. That single principle - default to the most comfortable option, offer the smoother-but-riskier one only to those who want it - guides every choice below.

The two dominant ways to travel a VR building sit at opposite ends of the comfort scale. Teleport locomotion is the default in Unreal's VR Template and the safest choice for review: you point the controller, an arc appears showing where you will land, you release, and you are instantly there. Because there is no continuous motion, there is no vestibular conflict - almost nobody feels sick teleporting. The cost is a small loss of spatial continuity: you jump rather than flow, so the felt sense of walking a long corridor is slightly broken. For most client reviews that trade is well worth it, and a good teleport (with a clear landing arc and a brief fade) feels natural within minutes.

Smooth (continuous) locomotion moves you through the world like a first-person game - push the thumbstick and glide forward. It preserves the flowing, embodied sense of walking the space, which can be lovely for experienced users and for conveying how a route feels end to end. But it is exactly the motion that triggers sickness in many people, so it must never be the unguarded default for a mixed audience. If you offer it, pair it with the comfort aids below and let the user opt in.

Between and around these sit useful variants. Room-scale walking - literally stepping within your tracked play area - is the most natural and comfortable of all, but limited to the few metres your room allows, so it complements rather than replaces teleport. Arm-swing or dash movement and world-grab (pulling yourself along by grabbing the space) are niche comfort compromises. The professional pattern is clear: teleport as the comfortable default, room-scale walking within the play space, and smooth locomotion as an opt-in for those who want continuous flow. Offer the choice; do not force the risky option on a first-timer.

Strip away the novelty and the real value of VR for architecture is true 1:1 scale: a metre in the model is a metre against your body. On a monitor you judge proportions; in VR at 1:1 you feel them - a 2.4-metre ceiling presses a little; a 3-metre one breathes; a corridor that reads fine in plan turns out to feel tight when your shoulders are in it. This is design information you cannot get any other way short of building the thing, and it is why a VR review catches problems a hundred renders miss.

That value is entirely dependent on the scale being honest, which comes back to the setup lesson. If your Datasmith import is at correct real-world scale (Unreal in centimetres) and your VR Pawn's floor origin sits on the building floor, then your standing eyeline lands where a real person's would and everything reads true automatically. The failure modes are worth naming: an import at the wrong unit scale makes the whole building feel like a doll's house or a giant's hall; a pawn floating above or sunk below the floor throws every height off. Verify scale deliberately - stand next to a known dimension (a standard 2.1m door, a 0.9m worktop, a 1.1m balustrade) and confirm it feels right on your body before you trust any judgement the review produces.**

A subtle point: individual IPD (from lesson 8.1) also affects felt scale slightly - a badly-set IPD can make a correctly-scaled room feel subtly off. So for a review where scale conclusions matter, set the headset IPD for each wearer. Do this, and VR becomes a genuine measuring instrument for space; skip it, and you are making confident decisions from a distorted model.

A handful of well-understood techniques let almost anyone last a full review, and Unreal supports them all. The most valuable is the comfort vignette (tunnelling): during continuous movement, the engine softly darkens and narrows your peripheral vision, shrinking the field of view just while you move and opening it again when you stop. Because most motion-sickness signal comes from the periphery, this dramatically cuts nausea for a small aesthetic cost. Pair it with snap-turn - rotating the view in fixed increments (say 30 or 45 degrees) with a quick blink rather than a continuous sweep - because smooth rotation is one of the most reliable sickness triggers of all. A gentle teleport fade (a brief dip to black on each jump) further smooths the transition.

Next, decide seated versus room-scale (standing). Seated is the most comfortable and the most accessible - many first-time clients do better seated, and long presentations are less tiring - but it sacrifices the walk-around embodiment. Room-scale standing gives the fullest presence and the most natural short-distance movement, but needs a cleared, defined play area and a tolerance for being on your feet. Offer both; default a nervous or first-time reviewer to seated with teleport, and let confident users stand.

Finally, safety is not optional. The wearer is blind to the real room, so every headset defines a guardian / chaperone boundary - you trace your safe area and a wall appears in VR when you approach its edge. Set it honestly, keep the physical space clear of furniture and cables, and have a spotter present for a standing session, especially with a first-timer who may step or reach unpredictably. A pause/recentre and an easy way to lift the headset should always be within reach. Comfort and safety together are what turn VR from a risky demo into a professional tool people trust.