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Re:VR optics and why IPD means too many things by EarthLaunch on Tuesday May 30, 2023 @09:02AM (#36124367)
Wow, what a fun and knowledge-filled article. It felt like reading Feynman.

Just casually browsing HN, this solves a problem that's been bugging me for months in my game: The world is scaled in feet/inches, while WebXR uses meters/cm to set ICD (virtual camera distance)! I think- based on my getting unusually nauseous.

I thought the solution was to scale the world, but there's more to it - and I think the solution is to reduce camera translation motion by the scale difference:

> Specifically if you translate your head sideways by the distance of your IOD, your left eyeball should now be seeing what your right eyeball was seeing. If it doesn't, the brain worries that something bad has happened, and makes you feel bad about it.

> Note that if you scale BOTH – you move the virtual cameras closer together, AND you reduce the in-game motion of the cameras due to head motion – everything is totally fine! The world just grew or shrank magically, but it all still works and you don't get nausea.

You may wonder why in hells a programmer would use imperial units instead of metric. It's to give the game a sense of being human-scale and pre-civilization. Why not just use metric and then convert everything to imperial for display purposes? Because then during debugging, units in logs constantly have to be converted to units shown, and the conversion isn't identical. It never bit me until VR!

Re:VR optics and why IPD means too many things by teddyh on Tuesday May 30, 2023 @09:08AM (#36124427)
Imperial units are not “human scale” any more, or less, than metric: https://xkcd.com/526/
Re:VR optics and why IPD means too many things by contrarian1234 on Tuesday May 30, 2023 @09:20AM (#36124551)
A 1 foot sandwich can be easily shared with 2, 3, 4 or 6 friends. And nobody has 5 friends anyway. There are no meter long sandwiches .. and if there were, you couldn't split it between 3 people. It's impractical. It's like if there were 100 degrees in a a circle.. You'd go nuts

Metric is for when you've made a mess of things and have completely given up on having nice round integer values

EDIT: This comment has been timed to coincide with when Americans wake up to defend me :) ~ USA! USA!

Re:VR optics and why IPD means too many things by pavlov on Tuesday May 30, 2023 @09:26AM (#36124603)
Splitting a meter-long sandwich between three people is easy. You give each person a footlong slice, and the remaining 8.6 cm to the dog.
Re:VR optics and why IPD means too many things by cassianoleal on Tuesday May 30, 2023 @11:20AM (#36125914)
Or, you know... You look at it, more or less find the one third point from the tip, cut it there, then cut the remaining larger part in half.

Which is probably the same way you'd do it if it was a 3.28ft-long sandwich instead.

Re:VR optics and why IPD means too many things by pavlov on Tuesday May 30, 2023 @11:52AM (#36126308)
Impossible. Ever since Hercules accidentally stepped on his lunch sandwich in the stables of Augeas, his 12-inch foot has been the standard measurement for Ideal Sandwich.
Re:VR optics and why IPD means too many things by teddyh on Tuesday May 30, 2023 @09:34AM (#36124700)
Depends on how thick it is, doesn’t it? Why the insistence on measuring the length? Couldn’t you just as easily have 1kg sandwiches?
Re:VR optics and why IPD means too many things by the-dude on Tuesday May 30, 2023 @09:29AM (#36124648)
In The Netherlands you can order beer in meters.
Re:VR optics and why IPD means too many things by dylan604 on Tuesday May 30, 2023 @09:41AM (#36124779)
At any spring break resort or in Vegas, you can order beer by the yard
Re:VR optics and why IPD means too many things by the-dude on Tuesday May 30, 2023 @10:08AM (#36125056)
Obviously a meter of beer is better than a yard of beer.
Re:VR optics and why IPD means too many things by dylan604 on Tuesday May 30, 2023 @10:28AM (#36125262)
Those last 3" (76.2mm) would just be foam anyways
Re:VR optics and why IPD means too many things by the-dude on Tuesday May 30, 2023 @11:09AM (#36125766)
Foam is measured in fingers.
Re:VR optics and why IPD means too many things by Symmetry on Tuesday May 30, 2023 @10:14AM (#36125125)
I dunno, a quarter meter sandwich seems just as natural as a quarter pound burger.
Re:VR optics and why IPD means too many things by regularfry on Tuesday May 30, 2023 @10:34AM (#36125342)
> It's like if there were 100 degrees in a a circle

There are 100 gradians in 90 degrees, does that count? They're probably supported on your calculator. https://en.wikipedia.org/wiki/Gradian

Re:VR optics and why IPD means too many things by HPsquared on Tuesday May 30, 2023 @01:37PM (#36127858)
It's a similar kind of thing to decimal time: https://en.wikipedia.org/wiki/Decimal_time
Re:VR optics and why IPD means too many things by vGPU on Tuesday May 30, 2023 @12:13PM (#36126614)
I could down a meter long sub by myself, and I’m fairly certain my dog could too. No need to share.
Re:VR optics and why IPD means too many things by interestica on Tuesday May 30, 2023 @10:13AM (#36125101)
I never understood why we never popularized a comparable metric measurement. A quarter-meter perhaps?
Re:VR optics and why IPD means too many things by snovv_crash on Tuesday May 30, 2023 @11:22AM (#36125941)
A decimeter is about 5 inches, which is the height of a cup, diameter of a burger, span across a hand, etc. To me that's a lot more human-friendly than a 'foot' being 12 inches.
Re:VR optics and why IPD means too many things by teddyh on Wednesday May 31, 2023 @10:04AM (#36138572)
“Hand” is already a historical unit, equalling almost exactly 10cm; i.e. 1dm. Horses are measured in hands.

<https://en.wikipedia.org/wiki/Hand_(unit)>

Re:VR optics and why IPD means too many things by blululu on Tuesday May 30, 2023 @10:55AM (#36125594)
You are citing a cartoon with a dick joke and a mom joke to say that metric is just as human oriented as imperial. Seriously: Imperial: 1 Foot ~ the length of some guy's foot. 1 Second - the duration of one heart beat. Metric: 1 Meter - some 1/10000 of 1/4 of an mis-measurement of the circumference of the Earth. 1 Second - stolen from the Imperial system cause 86 microdays did not easily divide by 10, 7, 24, 60, 30, 31 or 29.
Re:VR optics and why IPD means too many things by Lapha on Tuesday May 30, 2023 @01:19PM (#36127580)
The first mechanical clock that could accurately and reliably measure seconds was a pendulum clock with a length of one metre. Seconds and metres go hand in hand with the metric system.
Re:VR optics and why IPD means too many things by taeric on Tuesday May 30, 2023 @11:49AM (#36126267)
I mean, sorta? First, arbitrary numbers are arbitrary. But I can point to my foot and say that is about a foot in size. An inch is roughly one of my knuckles. A yard is roughly a step.

Even that comic you linked drives this home. None of them are referenced to humans. They are things we mostly know, sure. But they aren't based on a human. (Well, I suppose the mass ones have an amusing set of people listed.)

And this avoids the measures that, for my memory, just haven't made it to metric yet. Acre, Astrological Unit, Knot, etc.

Re:VR optics and why IPD means too many things by IYasha on Tuesday May 30, 2023 @12:23PM (#36126768)
"3 L - TWO-LITER BOTTLE"

Um, okay...

Re:VR optics and why IPD means too many things by HPsquared on Tuesday May 30, 2023 @01:42PM (#36127935)
As computer specialists, we should advocate a return of the Imperial system using fractions of an inch for measurements. This is because it fits perfectly into the binary floating-point system. There are no more problems relating to 0.1 being an irrational number in binary. It's all broken down into 1/2, 1/4, 1/8, 1/16 etc which in binary is 0b0.1, 0b0.01, 0b0.001, 0b0.0001