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DROIDdoesVR
Participant
August 9, 2013

Understanding IPD and how it relates to nausea

Just got my Rift this past Friday, totally awesome by the way. I’ve run OVR config utility and came up with 67.4mm for IPD. Then I went to see my eye doctor and had them read my IPD and they came up with 67mm. I told her I needed as accurate as possible. She then had me put a special pair of glasses on and stare at a red crosshair and she then took a picture of my eyes. She showed me how it worked on the computer and what part of the eye was actually being measured. She showed me a picture of my eye and made a reference to this tiny white dot at the back of eye. What is this dot and is it important in regards to settings? End result was that my official reading is 67.4mm. So at least for me, the Oculus IPD utility is spot on.

After receiving the rift and getting everything setup i quickly realized my pc is not capable of of playable frame rates for the rift. TitansofSpace showed 25fps on the frame counter. All games are very choppy even the ipd config settings tester is nausea inducing. My graphics card was a Radeon 4670 1Gb. A new graphics card fixed this issue. GTX760 to the rescue, now Titans frame rate bounces between 200 and 400 frames a sec. Vsync in other games works well. All options maximized. Ive only recently started to understand down sampling and how it effects the Rift. Currently from with the NVidia control panel I can set Rift DK to 1440 x 900 which has drastically improved the overall screen door effect and visual feel of certain games(HL2 being the best). Even with these new settings motion induced nausea is still present.
(side note) I’ve seen another post that down sampling from 1900x1200 or any resolution that uses the 16:10 ratio of the rift gives phenomenal results but I can’t seem to set this setting from within the NVidia control panel. My primary display has a max resolution of 1600x900 so I’m thinking that may be the reason

Back to the point. So my doctor wrote some notes to which i will attempt to transcribe here. I just want to know what they mean and how they correlate to Oculus settings.

PD(what she called it)
right eye (od) 33.2
left eye (os) 34.2
Single 67.4

What does knowing these numbers do for the overall gaming experience?

The problem I’m currently finding is there is no definitive all in one spot for FAQ for Rift knowledge. MTBS3d has a lot of knowledge but is randomly disbursed which causes me to read EVERY post hoping to find a tidbit of tangible knowledge that I can put to use.

Please forgive my rambling. Ever since I received my rift I’ve thought of nothing else. I have more question and some of those questions have questions. I know it’s a brave new frontier and many are in the same boat as I am. I am a gamer more than a programmer but I’d like to be more than that. But without the basic knowledge I don’t know where to start.

    6 replies

    uzimonkey
    Participant
    August 9, 2013
    I was just playing with the IPD settings, trying to mitigate the nausea a bit. Time in the rift helps, but having the right IPD helps more. IPD also helps a lot with image clarity, get the wrong IPD and everything looks blurry and you feel cross eyed. It's certainly something you'll want to get right.
    DROIDdoesVRAuthor
    Participant
    August 9, 2013
    I just did a little light reading on the subject of simulator sickness and it would seem that as far back as 1997 when the article was written they were aware of what causes simulator sickness even going so far as to point out that "using a wide field of view simulator display (Rift) combined with the absence of inertial motion cues is likely to increase motion sickness cues." Following this train of thought it would stand to reason that increasing resolution and refresh rate while lowering lag from sensors would increase motion sickness because the brain is clearly interpreting motion through the eyes but all other cues suggest a resting a state. It is this difference in states that causes simulator sickness.

    A possible solution was given that manipulating backgrounds can help offset one of the cues. My first thought is that camera bob in first person view would help trick the brain into believing the body was in motion. I cant remember when the last game I played had a character with head bob while moving. I've always hated it. Super smooth motion was what I wanted, however it seems that unnaturally smooth motion is a no-no in VR.

    here is link to article:
    http://www.hitl.washington.edu/publications/r-97-12/
    Walky
    Up and Coming
    August 9, 2013
    "DROIDdoesVR" wrote:
    She showed me a picture of my eye and made a reference to this tiny white dot at the back of eye. What is this dot and is it important in regards to settings?


    I'm no expert, but maybe it was the blind spot?. Perhaps this is used to calculate where the vision "center" (or whatever it's called) is, to get the "od" and "os" values?
    http://www.virtualreality.cl
    sh0v0r
    sh0v0r
    Up and Coming
    August 10, 2013
    One thing to remember about adjusting the IPD in demos is that all it does is adjust the distance between the cameras and the result of this is a change in scale perception. It will not improve image quality as it doesn't offset the distortion centre as this has to be aligned with the position of the lenses. If you adjust the value to an extreme you will experience issues particularly if the IPD is inverted and the eyes are swapped.

    The only reason you want to change the IPD is to try to make your perception of scale match your real world perception. This also requires adjusting the camera height. Having this match your real world perception helps your brain accept what it is seeing.

    The lack of horizontal lense separation to match your IPD is also a critical issue for image quality.

    Nausea related issues are caused by several things, for me it is most commonly caused by a lack of grounding in what I am experiencing. Your eyes seeing things that your brain finds irregular. Cockpit based simulators like my own Lunar Flight have a really strong frame of reference so nausea tends to be almost non existent. If I get out and walk around, using the XBox controller to adjust my rotation tends to make me feel a little ill because my body is not controlling the motion. Any thing that externally influences your look direction tends to make you feel off also moving at super human speeds laterally can be bad also.

    Lastly I think performance is a big issue, you really want to have a solid vsyncd 60 FPS to reduce eye strain and headaches. When the HD kit comes along you're going to want a fairly powerful machine. I see this as a problem for the large scale adoption of the technology by the masses. Many people are going to buy one and have a fairly poor experience on low to mid spec machines and they will be a potentially larger part of the market.
    DROIDdoesVRAuthor
    Participant
    August 10, 2013
    I had to up my graphics to have a playable frame rate. Now I have an excessive amount for ALL my existing games. Titans of Space frames counter shows me bouncing anywhere between 200 and 400. Vertical sync works with zero issues as well. Skyrim, which is my most intensive game now plays at Ultra settings. I don't know how to check frame rate with this though.

    Realistically, Oculus will need to put a disclaimer on the box specifically recommending hardware. Fortunately though said hardware should play basically anything on the market today.
    tomf
    Participant
    August 10, 2013
    "DROIDdoesVR" wrote:
    Then I went to see my eye doctor and had them read my IPD and they came up with 67mm. I told her I needed as accurate as possible. [...] End result was that my official reading is 67.4mm. So at least for me, the Oculus IPD utility is spot on.


    I'm very happy our simple tester was so accurate, but in VR a difference of a millimeter of IPD is really not going to make much difference. Every time you put the Rift on your head you're probably about a millimeter different from the last time anyway.

    "DROIDdoesVR" wrote:
    Ive only recently started to understand down sampling and how it effects the Rift. Currently from with the NVidia control panel I can set Rift DK to 1440 x 900 which has drastically improved the overall screen door effect and visual feel of certain games(HL2 being the best).

    Like many games, HL2 has an MSAA setting, which does the same thing as downsampling, but more efficiently (i.e. higher or more stable framerates - important for VR). I would reset the resolution to the native one (1280x800) and turn MSAA in HL2 up to the max, which I seem to recall is 8x.

    "DROIDdoesVR" wrote:
    So my doctor wrote some notes to which i will attempt to transcribe here. I just want to know what they mean and how they correlate to Oculus settings.

    PD(what she called it)
    right eye (od) 33.2
    left eye (os) 34.2
    Single 67.4


    I am not an ophthalmologist, but my guess would be:
    "OD" - Offset Dexter - the offset from your nose to your right eye's pupil.
    "OS" - Offset Sinister - the offset from your nose to your left eye's pupil.
    And then 67.4 is the total separation, which is just those two added together, and what we call the IPD.
    Tom Forsyth - OculusVR coder
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