Nausea when large monitors while playing videogames: I show why it happens.

[Jeremy Duncan]

[quote=”Jeremy Duncan”]
First I will list two facts: flicker fusion threshold, and parallax motion estimation.
Then I will post a bit of math.
Thirdly I will post a conclusion.

[b][size=3]Section a, the facts[/size][/b]

[b]Flicker fusion threshold[/b]

“If the frame rate falls below the flicker fusion threshold for the given viewing conditions, flicker will be apparent to the observer, and movements of objects on the film will appear jerky. For the purposes of presenting moving images, the human flicker fusion threshold is usually taken as 16 hertz (Hz).”
[url=http://”http://en.wikipedia.org/wiki/Flicker_fusion_threshold”%5DLINK%5B/url%5D

[b]”occlusion”[/b]

What is occlusion? I will quote a article on it:

“In IMAX, in which people are sitting close to a giant screen, the periphery of the screen is more difficult to discern and the rectangle becomes relatively unimportant.

The idea behind IMAX is to immerse you in the experience.  So people who shoot IMAX movies have to think about a different kind of composition. I’m concerned with the stereoscopic cinema so my remarks are predicated on that interest.

In the stereoscopic cinema, the rectangular boundaries are important because of the well-known effect of the conflict of stereoscopic cue of parallax and the extra-stereoscopic cue called interposition.  If off-screen (negative) parallax values are occluded by the screen edges–and this is especially true for the vertical edges of the screen–there will be a conflict of cues, which some people (possibly most people) interpret as a region of confusion.

Some people may say that the image looks like it’s pulled back into the plane of the screen; some will report that the image looks odd.  In any event, it’s something that has to be dealt with in the conventional stereoscopic cinema and doesn’t need to be dealt with in IMAX because the screen is so large that it’s hard to see the edges of the surround.

(Another thought to put into the mix that might further confusion rather than understanding is that we are in a time of transition in which people are learning how to look at stereo movies and maybe with the passage of time the screen edge conflict will come to be accepted.)”

[url=http://”http://lennylipton.wordpress.com/2008/03/20/compositional-differences-real-d-vs-imax/”%5Dlink%5B/url%5D

[QUOTE=Lee Stewart;17246277]Please explain to me what exactly are; “motion induced parallax errors.”[/quote]

Below is what is Motion Parallax

“If the man above fixates on the single tree in the middle and starts walking to the right, the four trees in the back will appear to move to the right while the two trees in the front will appear to move to the left.  This phenomenon is called motion parallax and is one of the cues to depth.”

[url=http://www.yorku.ca/eye/Motion%20Parallax.htm]http://www.yorku.ca/eye/Motion%20Parallax.htm[/url]

If you have a cup that might be dirty you tilt it to look inside.
Same as if a pop can rim may be dirty, you tilt it and look at it.

[url=http://www.youtube.com/watch?v=UeF-kCr_vyo]http://www.youtube.com/watch?v=UeF-kCr_vyo[/url]

A error is when the brain tells the eyes it can’t work out what’s happening, so the eyes work harder and after a while the eyes tire then the brain works the problem out itself, then it too gets tired of piecing together the Motion Parallax and the viewer feels sick.

[b][size=3]Section b, the math[/size][/b]

[code]parallax motion estimation done by the eye and brain + (flicker fusion rate kind of jerkiness in the rate of video and audio in regard to relative tracking of the eye, ear) = confusion %[/code]
[code]Example 1: parallax motion estimation + irritatingly fast audio and video = Confusion 90%[/code]
[code]Example 2: Parallax motion estimation + irritatingly fast audio but the video is not too fast for the eye to follow = confusion 40%[/code]

Confusion % is when the brain does not understand parallax motion and gets confused.

[b][size=3]Section c, the conclusion[/size][/b]

The flicker fusion threshold sees jerkiness if the framerate drops to  too low a number. But I want to use the flicker fusion threshold so I can focus on the problem it poses: jerkiness.

If the eyes are jerking around too fast to follow the motion, or the ears are listening to chipmunk singing at 200% speed it’s uncomfortable to listen too.

With this jerkiness of the eyes and ears the brain is still trying to figure out the motion parallax.
And the largeness of the screen makes the need to figure out motion parallax more than if it was a small screen because of the 3d effect a large screen poses compared to a small screen.

“In IMAX, in which people are sitting close to a giant screen, the periphery of the screen is more difficult to discern and the rectangle becomes relatively unimportant.

The idea behind IMAX is to immerse you in the experience.”

So the periphery of the screen is less visible when using a large screen so the need for the brain to judge motion parallax increases as you are more immersed.

So what does this mean?
1.) the large screen makes the experience immersed so the brain tries to figure out motion parallax.
2.) the jerkiness of the audio and video makes watching and hearing it uncomfortable.
3.) This is my final conclusion and why I’m posting this: This equals a potential problem with the immersed experience causing the brain confusion as it tries to work out the parallax motion. The problem can be overwhelming so the brain and eyes cannot operate under these circumstances and give up and the viewer feels nausea and motion sickness.
[/quote]

[b][size=3]Section D, the Inner Ear[/size][/b]

“we have many different senses that help us detect motion – our eyes see movement, our muscles feel it, our ears hear it, and our inner ears sense acceleration and orientation of the body.  These sensors are spread out all over the body, so if your head is moving at a  different rate from the rest of your body, you might feel ill. Your inner ear alone has two different ways of sensing movement, and sometimes they send different signals to your brain, causing you to feel motion sickness.

The worst thing for motion sickness is periodic motion, motion that repeats in a consistent pattern, like a boat bobbing up and down on waves. We are most likely to get motion sickness with waves in the range of 0.15 to 0.25 Hz (0.15-0.25 cycles per second, or 4-7 seconds per cycle). The next time you start to feel ill from turbulence in an airplane, take out your watch and count how many times the airplane rises and falls in a minute. If it’s around 9-15 times a minute, that’s right in that zone where the most people will feel sick. I always feel better after doing this calculation, but maybe it’s because the turbulence is usually over by the time I’ve finished.

So why did I feel sick playing the video game? I wasn’t even moving! I was experiencing a close cousin of motion sickness called simulator sickness, which has its roots in the same bodily functions that produce motion sickness – your eyes tell you that you’re moving, but your inner ear and muscles say that you’re not. Pilots get simulator sickness all the time during flight training, as do students using driving software, and people watching movies. The bigger the screen the more you’ll feel it, as anyone that has gone to an IMAX movie knows.

I experienced a bad design that REALLY made me feel sick a several months ago when I was watching the news. There was a moving graphic behind the talking heads and illustrations that was like someone walking between two concentric circles of columns. The columns moved off screen to the left and to the right, but at different speeds – the outer circle moved off screen faster than the inner circle. You can watch another news video with the same moving graphic [url=http://”http://www.msnbc.msn.com/id/21134540/vp/27415779″%5Dlink%5B/url%5D – make sure you hit the fullscreen button to get the full effect. After watching this for a few minutes on my widescreen television I felt very ill and had to turn off the television until the segment was over.  Why did I feel ill? Because my eyes were seeing movement (two different types!) while the rest of my body was telling my brain I was sitting still. This is similar to what happened when I was playing Wolfenstein.  Modern video games continue to have this problem, especially because of advanced movement algorithms like head bob, where the horizon bobs as you walk, or gun bob, where the foreground bobs. This periodic motion can make players feel ill, especially if the game has both at the same time.

Avid video game players that tend to get motion sickness have many techniques they use to minimize it, such as building up tolerance over time, using a smaller screen, and taking anti-nausea medications. But designers can help avoid causing motion sickness by using movement carefully. I’ve seen other news videos that used moving graphics without the same impact on my gut because the movement was all at the same speed (for example, watch the first 30 seconds of this video [url=http://”http://www.msnbc.msn.com/id/3032619/vp/27415779#30917307″%5Dlink%5B/url%5D). Video games can provide settings to turn off features like head bob. The Boeing 787 Dreamliner treats its passengers to very smooth ride by using vertical gust suppression [url=http://”http://www.msnbc.msn.com/id/19421451/”%5Dlink%5B/url%5Dto counteract turbulence and wind gusts. If you have motion, avoid repetitive motion in the 4-7 seconds per cycle zone; make the repetition either faster or slower.”

[url=http://blog.humancentric.com/bad-design-makes-me-sick/]http://blog.humancentric.com/bad-design-makes-me-sick/[/url]

In the article we see the effects of bob/jerkiness causing nausea.

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