Stereoscopic 3D/VR

[ThreeDeeJay]

Is your feature request related to a problem? Please describe.
I know there's been requests and attempts in the past, but are there any plans to officially implement stereoscopic 3D/VR?

Describe the solution you'd like
Would be nice to make Celestia render in 3D/VR.

Describe alternatives you've considered
I was able to enable stereo rendering by using the MESA OpenGL to Direct3D 12 wrapper with my NVIDIA 3D Vision setup (driver 425.31 + RTX 2080 Ti)
https://airtable.com/appByPZJsOQSVGDID/shrAfMuGs1IOIEpRT?uMgeK=recRfaZDGmmhI0bMU

But the problem is that background stars/galaxies/et are rendered at a different relative depth than the nearby objects, which breaks the stereoscopic coherence. Like if you cross your eyes (or view with a proper 3D display/VR) you'll notice some distant stars are rendered in front of Earth

I also found a plugin but it's paid and I'm not sure if it's still on sale and compatible: https://www.youtube.com/watch?v=3EXguHOVfzU

Additional context
SpaceEngine has an option for quad buffer OpenGL stereo 3D, which might be the easiest one to implement, and it was thought to only be supported by professional GPUs like the Quadro but it actually works quite well on my 3D-specific PC build (driver 425.31 + RTX 2080 Ti), though quad buffer support is extremely rare so it might also be a good idea to just add an option to render commonly supported layouts like side by side (SBS), top and bottom (TAB) and row/column interlaced, and virtual reality (I'd suggest OpenXR).

[levinli303]

Celestia is on Apple Vision Pro. I don’t have device but the simulator Apple provided is somewhat enough to make it shippable. It renders to two Metal frame buffers with the left/right eye transform matrices provided by Apple’s API

https://apps.apple.com/us/app/celestia-vision/id6476618172

As for Windows/Android VR, I think a physical device is required to develop for the platforms and sadly I don’t have any device to develop for them.

[ThreeDeeJay]

For the software side, there's Android XR, or Cardboard which I think is older but still getting updates.
So f you're interested, the cheapest option would be a smartphone mount like a Google Cardboard, go for a better mount like the Samsung Gear VR or some cheap alternative in between. Then you could consider getting a standalone headset like a Quest or a Pico, some of which can also be used in PCVR, which might be trickier to implement.

But in the meantime, wouldn't 3D be relatively easy to implement?
Basically it's just the left and right views, preferably with customization on how far apart the cameras are and where they converge to adjust the relative depth of the display. SBS layout would be compatible with most devices, and since the app's already OpenGL it might not be too hard to implement quad buffer stereo. 🤔

[levinli303]

Per Google:

The Android XR emulator is not supported for Unity or OpenXR apps.

overall I think developing for a more popular platform like Quest makes more sense or if Android XR matures as a platform. The device is not super expensive but it is not zero and Celestia project doesn't have sponsors.

As for adding support for rendering left and right eye frame buffers with existing frontends, I don't think any dev wants to touch renderer code for Win32 here, it is rather old.