`keep_3d_linear` causes the output to be too dark on Linux

[kb173]

Our VR output was too dark on Linux - as dark as the VR mirror view on Windows. After some testing, we noticed that by setting keep_3d_linear to false, the output seems to be correct. We've tested this with the same project on 2 different Linux machines (where the output was too dark without keep_3d_linear = false) and on 1 Windows machine (where, as described in the README, keep_3d_linear = true is preferable). In both cases, we used a Valve Index.

I'm not sure if this is something that should / can be fixed in the codebase, or just something to document in the README - I just want to avoid people from being as frustrated with this in the future 😉

[beniwtv]

Heya!

It's in fact mentioned in the README as you've noted - but with HDR in mind (and not especially Windows/Linux). In theory, there should not be any difference between Linux/Windows - or at least so we thought.

So far I didn't notice it being too dark on my Linux machine - but then again I haven't really compared much to Windows.

Possible reasons could also just be a Linux driver issue, or a different version of the OpenVR library between the two. Or even a bug in OpenVR (yeah we had that too).

Not sure how useful it will be chasing this, seeing OpenXR becoming the standard.

[kb173]

Hi @beniwtv! Thanks for the response.

I noticed the note about HDR in the README, but what should be added in my opinion would be a note to (potentially) disable keep_3d_linear on Linux if the output appears too dark. Interesting that you didn't seem to have this issue though - just out of curiosity, were you testing with an Nvidia or AMD card? Both machines we tested on had an Nvidia card with the latest proprietary drivers.

But you're right, if OpenXR will gradually replace this plugin, it's probably not worth it to put more time into this. (But, on that note: maybe a mention of OpenXR being the recommended plugin to use could be added into the README of this one? I loosely followed Godot's OpenXR support, but didn't know it can actually already replace this one in many cases.)

[beniwtv]

I only have access to AMD cards at the moment, so a driver bug in Nivida or OpenVR/Nvidia could be a thing, too, yeah.

[beniwtv]

Oh and on the note of OpenXR: I think it doesn't do overlays yet (if I haven't missed anything as I was quite busy these months), but I plan to add that as we did for OpenVR.