OpenXR compatibility no longer outputting correct colors on desktop

[BastiaanOlij]

Tested versions

• Reproducable in 4.5-beta (46c495c)
• 4.5-dev5 gives completely wrong results but I think that is an already fixed regression
• Works correctly in 4.5-dev3 , not sure about dev4

System information

Windows 11 - SteamVR - SteamLink on Quest 3

Issue description

Noticed that the output to screen has suddenly gone wrong in SteamVR.
Preview on screen is in the wrong color space (looks like missing sRGB conversion, which would likely also lead to banding in headset in dark scenes).
Colors in headset are correct and match editor.

Compatibility in 4.5-beta (wrong):

Mobile rendere in 4.5-beta (correct):

Compatibility in 4.5-dev3 (correct):

(I tested dev5 as well but that completely wrecked things)

Steps to reproduce

Open up any OpenXR project in compatibility renderer.

Minimal reproduction project (MRP)

Project used for screenshots is: https://github.com/godotengine/godot-demo-projects/tree/master/xr/openxr_hand_tracking_demo

[devloglogan]

An even worse regression was present in 4.5-dev5 where the desktop preview output is like a red depth-buffer.

I did a bisect and it looks like #107345 fixed it from that, to what we currently see. Per clay's comment on that PR, perhaps something in #106267 caused this?

[BastiaanOlij]

@devloglogan I noticed that too but since that seems fixed in beta, I skipped over that version.
It is possible that in fixing that, the sRGB conversion got messed up.

[BastiaanOlij]

I did a bisect and it looks like #107345 fixed it from that, to what we currently see. Per clay's comment on that PR, perhaps something in #106267 caused this?

Indeed, that is likely the cause. Due to the way that OpenXR works we create an RGBA8_SRGB texture instead of an RGBA8 texture as we use internally. That would do a hardware SRGB -> linear conversion when reading from that texture and indeed explains the issue.

I'll find some time to resolve this, now that its a fragment shader I can look into re-introducing lens distortion as well, which is something we lost.