Why Multiple Displays are (much) Better than VR Headsets

July 23rd, 2019

About VR Headsets

There is increasing interest in using new generation “consumer” VR Headsets such as Facebook’s “Oculus” and HTC’s “Vive” as display devices for simulator-based training.

The idea is simple: when you turn your head, that movement is detected by “head-tracking” electronics in the headset and then transmitted to your computer. After that, your computer “re-draws” what you see on the two small displays inside the headset placed in front of your eyes.The problem is, lots of people experience motion sickness when objects are moving in the simulated world and especially when you are moving too e.g. at the controls of (simulated) mobile equipment.   (One automotive manufacturer told us that 80% of his trainees experienced such motion sickness.)

The most obvious symptom of such motion sickness is nausea but others are blurred vision, vertigo, dizziness, fatigue and headache, even hours later.

Well, that motion sickness is due to two different problems.

First, when wearing a VR Headset, your field-of-view is limited to what’s directly in front of you, much like the “blinders” that prevent a horse from seeing side-to-side while racing. For that reason, you must turn your head to “see” left and right, and to see up and down.

That leads to the second problem, namely the time delay between turning your head and “seeing” in the new direction (also called “lag” or “latency”), because typical computers just can’t “keep up” with typical head movements.

Here are the technical details: the frame rate of typical simulation software (and video games) is about 30 Hz, meaning that about 30 times a second, your computer must “notice” the movement of your head, decide what to change now that you are looking in a new direction, perform lots of calculations associated with those changes, and then “re-draw” what you see inside the VR Headset. And all that takes “lots” of time.  (Of course, you can avoid this time delay by learning to turn your head s-l-o-w-l-y.)

Why Multiple Displays are (much) Better

In the real world, you can turn your head as quickly as you want and you always see something new, i.e. there is no “time delay”.

More importantly, when you look forwards, you see not just forwards but also to left and right and up and down. And that peripheral vision is key to operating real heavy equipment in the real world, whether you’re working with a forklift to place a palletized load on a shelf, or working with an excavator to dump material into the bed of a haul truck.

The fact is, you count on being able to see to the left and right and up and down while you work, and that’s preserving a “natural” field-of-view is so important for simulator-based training.

Indeed, you can do just that with three “big screen” displays set up in front of your simulator controls to provide a panoramic field of view of 180 degrees. (And when it’s important to turn your head to look backwards e.g. when driving a forklift or backhoe loader backwards, just add another “big screen” display set up behind your simulator controls.)

Fortunately, the growing popularity of home entertainment systems has brought the price of such “big screen” HD (and now 4K) TVs within the reach of every training budget, even as the size of typical “consumer” models continue to increase from 42” to 55” to 60” or more. (Bigger displays will “fill up” even more of your field of view, making the simulation experience even more “immersive”.)

You’ll even find that the price of four such displays can be less than the price of a single VR Headset.

6 More Reasons Why Multiple Displays are (much) Better

We can identify six additional limitations associated with VR Headsets.

First, wearing a VR Headset limits what you see to just the simulated world. For this reason, it can be difficult, for example, to reach for a forklift lever with your right hand (in the real world) because you cannot “see” the lever or your hand. (More expensive VR Headsets attempt to overcome this problem by adding cameras to “superimpose” what the cameras “see” on top of the simulated world to create “augmented reality”, at added cost. Alternatively, there are VR “gloves” with built-in sensors to “capture” the position and movement of your hands, in order to create virtual hands that can be seen the simulated world presented inside the VR Headset.)

Second, the weight on your head, and the display fitting tightly over your eyes (to block out the real world around you), makes it uncomfortable to wear a VR Headset for extended lengths of time.

Third, the VR Headset must be connected by a cable to your computer (wireless connections are too slow) and that cable can “get in the way” when you move your head. (Of course with multiple displays, you can always move your head freely, i.e. there is no such interference.)

Fourth, when wearing a VR Headset, only you can “see” what’s going on. So if an instructor wants to monitor your progress by watching you at work, that instructor will need some kind of conventional display in any case, at additional cost.

Fifth, because the displays inside the VR Headset are so close to your eyes, the visual display appears “pixelated”, i.e. you can notice the tiny picture elements (pixels) that together create the visual presentation. This isn’t a problem with big screen displays because they are positioned much farther away from your eyes, and so visual quality is superior.

Finally, when sharing a single simulator “station” among many trainees, the VR Headset must be adjusted each time (everyone’s head is different), and that means extra wear-and-tear that can quickly lead to damage, not to mention problems associated with personal hygiene. (There’s a reason why people don’t share baseball caps or bicycle helmets.)

Clearly, using multiple displays has none of these limitations.

The Bottom Line

Today’s VR Headsets are simply too “primitive”, too fragile, and too costly for “industrial strength” simulator-based training.

And in every way (except “transportability”), multiple “big screen” displays will always deliver superior support for hour-after-hour simulator-based training

Additional Reading

“The Science of Simulation”, MS&T – The International Defense Training Journal, Halldale Group, June 2019, https://militarysimulation.training/articles/science-of-simulation/

“The Virtual Reality Head-Mounted Display Oculus Rift Induces Motion Sickness”, J. Munafo, M. Diedrick, T. Stoffregen, Experimental Brain Research, Volume 235, Issue 3, March 2017.