This post got significantly edited on 4 August 2019. The original version is kept below for reference only.
Well, after reading through a number of discussions related to FOVs, PPDs, etc. I have to admit I have underestimated the complexity of this issue. Therefore this post is completely re-edited to reflect the most accurate data and methodology “out there”.
Notes to the methodology and sources:
- All values and calculations are per one eye only (therefore the FOVs are not for the whole HMD but for one eye only).
- The calculations are done for horizontal as well as vertical FOVs.
- FOVs are rendered FOVs, so it is an upper limit of what can be seen (i.e. Valve Index’s value is similar to Vive Pro’s but the Index allows to see more of the rendered FOV than the Vive).
- Rendered FOVs come from a function in OpenVR IVRSystem::GetProjectionRaw which returns the tangents of the angles of the left, right, bottom and top clipping planes for each eye projection. Refer to risa2000 post on pimax forum for further details.
- Horizontal and vertical rendered FOVs values are sources from a table created by Durante using the OpenVR function above (reddit thread also here). HP Reverb values were sourced from @BeachAV8R on Mudspike forum.
- I am aware of the ROV room in SteamVR that allows users to measure various qualities of their HMDs. After having read through many discussions and having tried it myself, I decided to disregard this method of assessing the visible FOV in favor of the rendered FOV methodology instead.
- For Pimax, the vertical rendered FOVs is with parallel projection off.
- Panel utilization factor not accounted for.
- Image warping and optics effects not accounted for (check this thread for more details; nevertheless, the vertical PPD of the Pimax 5k+ in the thread is very close to the one in the table below; not so for the horizontal one though).
And here is the resulting table:
Please do read the discussions linked in this post for better understanding of the topic.
Thanks all for contribution. I believe it led to a better result (=table).
---------- Original post: OBSOLETE ----------
just out of curiosity I made a little table comparing the main VR headsets’ displays in terms of
- pixel count
- sub-pixel count
- pixels-per-degree (PPD)
The idea came out of a HP Reverb topic where the PPD was discussed as well (by @fearlessfrog):
Resolution on its own does not say much as it needs to be judged together with the FOV (more pixels stretched over wider FOV may equal to less pixels stretched over narrower FOV - in terms of PPD of course).
The methodology (a simple one, this is not rocket science )
- resolution and FOV are horizontal
- Pentile arrangement counts 2 sub-pixels per pixel
- RGB arrangement counts 3 sub-pixels per pixel
- binocular FOV is 120 degrees as per the image below; this means that I suppose that both displays show +/- the same FOV for headsets with FOV under 120 degrees; for headsets with FOV higher than 120 degrees the calculation is adjusted to provide for the higher FOV
Note: For the Pimax 8K, the table counts with resolution 2560x1440 since this is the resolution to which the picture is rendered and only then it is upscaled to 3840x2160.
Btw. human eye PPD is believed to be around 60.
Well, it seems that the table is an add for the HP Reverb but do not forget that the table is just numbers and it disregards other qualities of the headsets.
In case you see an error, please let me know. I am happy to update the table if the need be.