I think some of the confusion here is between the apparent ‘roughness’ caused by gaps between pixels and such, and actual readability caused by not having enough pixels.
Apparent roughness can be satisfied with even the lowest capability headsets, like the Oculus CV1, as long as gaps between pixels are not too visible. Additionally, this may be ‘faked’ by adding diffusion, increasing overlap, etc. Which is why I keep telling people that for roomscale and such, the high resolution of the 8kX is not as amazing. It does make some things like vegetation in HL Alyx look better, but it’s not as much as a must have.
Actual resolution, cannot be faked with any magic. Only one thing counts - Pixels Per Degree (PPD). This is computed from exactly three numbers. Real pixels (not subpixels) along one axis, divided by field of view in degrees across that axis, multiplied by any concentration of pixels done by the lenses (so far this has been exactly 1 in all reported cases). Because these numbers have a ~40% margin of error due to such things as not all pixels being used, calculated PPD is a rough estimate. Thus, actual measurements and qualitative evaluations should be given considered as well.
Actual resolution, the 8kX is at the very top, and so it is the best for things like Virtual Desktop, where readability counts, not just smoothness.
@PimaxUSA The PPD numbers cited by that Wikipedia article, while resulting in similar relative rankings, in absolute terms, are consistently rather far from my own and some comparable estimates. IIRC, my own calculations place the 5k+ at 17 PPD and the Oculus CV1 at 11 PPD, not 21 or 12 and 9 respectively. Also, notice that two very different numbers are cited for the 5k+ depending on horizontal FOV setting. I think that article needs serious work on its PPD numbers.
@SweViver If your macro camera setup could be calibrated to exactly focus 10 degrees to a specified number of pixels on its sensor, then your Through-The-Lens photos could be used to put an exact number of VR headset pixels-per-degree count, ending the era of relative approximations.
EDIT: Additionally, at resolutions below a 5k+ at 1.75 Total SR, a lack of pixels per degree does create a severe ‘fog’ effect in any VR application. This is a sharp threshold, below which, an awful grey haze suddenly appears. Mathematically, it is due to the sudden loss of dynamic range as color information from multiple pixels is summed into a single pixel, resulting in colors not being as deep. Especially, the sharp transition was easily noticed in PavlovVR, which renders at very sharp contrast. PimaxUSA was definitely correct in calling this out.