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Comment by forgotmyoldacc | Hacker News Reader

> Panasonic's MeganeX, which uses 2560x2560 120Hz micro-OLEDs, is finally being released in the spring for <$1000

The FoV is probably going to be worse than current gen headsets (Index, Quest 1/2, etc).

A lower FOV actually translates to better PPD. You can use a basic formula: sqrt(hRes^2+vRes^2)/FOV. So a 100 degree FOV would give you about 36PPD, but a 90 degree FOV would actually give you an even better 40PPD. 60PPD is Apple's target for a "Retina" display, although there's a strong argument that you need double that at least for line pairs. For computer work purposes, we really should only care about matching PPD of a monitor. 36PPD is about equivalent of a 27" FHD monitor from 2ft/60cm: https://qasimk.io/screen-ppd/ and is probably good enough to start on focusing on other aspects of your optical design.

For a bit more nuance, here's a nice article that talks about how rendering geometry maps to FOV https://risa2000.github.io/vrdocs/docs/hmd_fov_calculation.h... although notably this does not account for the distortion shaders used in modern HMD pipelines to correct both for geometry and chromatic aberrations. There can be more techniques for improved text rendering, like what Oculus does with their timewarp layers: https://www.facebook.com/permalink.php?story_fbid=1942692682...

For those interested, here's some discussion focused on optimal text rendering in 3D engines: https://bgolus.medium.com/sharper-mipmapping-using-shader-ba...

In a previous thread, @kanetw was actually kind enough to chat in more detail about some of the Simula's optical specs: https://news.ycombinator.com/item?id=29930547

For some basic references of different aspects of visual fidelity for HMDs, this old writeup by UC Davis professor/VR researcher Oliver Kreylos is a good place to start: http://doc-ok.org/?p=1414

If you're interested you can surf through his blog for lots of insights. Also, this doc is one I just found that does a good job covering a bunch of the optical issues with HMDs: http://almalence.com/doc/SPIE-11765-23-V3/Near-eye_display_o...

The above formula only holds for diagonal FOV, which is higher than hFOV/vFOV.

The formula for e.g. PPD in the h-direction, assuming uniform pixel distribution, would be hPPD = hRes / hFOV. With a uniform distribution, 2448px at 100deg FOV would be 24.5.

We don't have uniform pixel distribution, as the human eye cannot resolve well where it can't gaze. So we magnify more wherever you can actually point your pupil at, and less towards the periphery. That way we retain eye-acuity while allowing us to "waste' less pixels where they aren't required.

We maintain >32 PPD within +- 15 degrees of eye rotation, which accounts for 86% of eye rotations.

Higher PPD is good, but with the lower FoV it's going to feel like you're looking at your computer screen through binoculars.

The MeganeX I believe is using the Kopin P95 optics. 95 degree diagonal FOV should be roughly similar to the CV1. Slightly less immersive than the latest headsets, but for virtual workspaces should still be fine. Remember, that the normal hFOV when looking at 32" display from 2ft away is 60 degrees (27" display is closer to 50 degrees). Due to center sharpness dropoff for most HMD optics, you will mostly be ignoring the edges anyway.

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