VR resolution and stereoscopic possibilities

Started by Dune, October 03, 2019, 05:24:12 am

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Dune

I have been asked to make a render for a VR headset, but I wonder what resolution would be good enough and best. Good enough may be good enough, as the payment is really meagre. But I was also wondering about a stereoscopic view, just to see if that would work. That would mean two renders of course, and then less than good enough may be good enough ;)
So, I see a stereo tab, and assume left and right are the ones to render. But what about inter-axial separation? Is default okay? Or does it depend on the headset?

Any advice is greatly appreciated.

Hannes

Just out of curiosity: do you know cross eyed viewing? If so, you could create two low res test images, and easily check, if it works.

Dune

Yes, but this is going to be equirectangular, and I guess it's kind of strange viewing. Maybe opening two instances of FSPviewer next to eachother and then cross the eyes  ??? , but I don't think I'll manage to check the exact inter-axial separation. Just waiting for an expert, I guess.

Dune

Nobody knows?
He're something else I found from google, but I don't understand it.

360° images

    360° images can be stored as png, jpeg, or gif. We recommend you use jpeg for improved compression.

    For maximum compatibility and performance, image dimensions should be powers of two (e.g., 2048 or 4096).

    Mono images should be 2:1 aspect ratio (e.g. 4096 x 2048).

    Stereo images should be 1:1 aspect ratio (e.g. 4096 x 4096).


Why should stereo images be 1:1 ? And does TG do that automatically, don't think so.

WAS

Quote from: Dune on October 04, 2019, 02:28:59 amNobody knows?
He're something else I found from google, but I don't understand it.

360° images

    360° images can be stored as png, jpeg, or gif. We recommend you use jpeg for improved compression.

    For maximum compatibility and performance, image dimensions should be powers of two (e.g., 2048 or 4096).

    Mono images should be 2:1 aspect ratio (e.g. 4096 x 2048).

    Stereo images should be 1:1 aspect ratio (e.g. 4096 x 4096).


Why should stereo images be 1:1 ? And does TG do that automatically, don't think so.


Considering it's creating a stereoscropic effect 1:1 seems reasonable.


As far as resolution, the sizes they give are a good rule of thumb. Anything at or below 1080p as been known to cause motion sickness worse than higher resolutions.

Additionally, framerate needs to be a steady 60fps+ if video

I tested the original Oculus and, as many found out the original test model of 720p while amazing, cause severe motion sickness. The 1080p model wasn't much better. And being prone to this, I wasn't nearly as effected on my friends 4k setup with Fallout at 120fps.
Check out the Terragen Community on Facebook: https://www.facebook.com/groups/Terragen.Galleries/

Dune

Quote from: WAS on October 04, 2019, 04:29:19 amConsidering it's creating a stereoscropic effect 1:1 seems reasonable.
But it still needs to be equirectangular to be projected on the sphere, so how's that happening?

Hannes

Ah, I didn't read it correctly. So you need to make a complete seamless 360° stereoscopic image. Actually I know how to create a simple rectangular stereoscopic image. But is it possible at all to create one equirectangular stereoscopic image made of the left eye image and the right eye image? Actually if you look at your final image wearing VR glasses and you turn your head 180° I assume left and right are switched?
Just thinking...

Dune

I have to think too, just tested a set of left and right eye in 2:1 ratio, and there's a difference indeed, but I have no oportunity to test it in glasses. I don't think left and right eye should be switched, you just look at the back of the sphere. But it's hard to comprehend, hence my query for experience....

Dune

Really, has no one ever tested the stereoscopic, equirectangular TG possibilities?

Hannes

I'd love to test that, since I'm a big fan of stereoscopic imagery, but I don't have any viewing device that doesn't make me throw up after five minutes. Nevertheless I'd like to know as well, if this is possible.I'll follow this thread (if there are any contributors...).
Good luck, Ulco!

Dune

Thanks, Hannes. I thought Matt and Oshyan had been busy with this stuff (you know, the contest and all), so I hope they'll chime in.

Matt

October 06, 2019, 03:23:42 pm #11 Last Edit: October 06, 2019, 03:39:22 pm by Matt
Hi Ulco,

Resolution: The requirements depend on the resolution and field of view of the headset.

Aspect ratio: If you see recommendations for a 2:1 ratio for mono and 1:1 ratio for stereo, that's simply because the 2:1 left eye and 2:1 right eye images are stacked one on top of the other and then separated into left and right images by the software at run-time. Whether the images are stacked this way really depends on the viewing software.

Inter-axial separation: This is the distance between the eyes in world space. If you want to depict a realistic sense of depth this should be left at the default. However, if you use an unusual scale in your scene then you'd need to adjust this, otherwise the viewer may perceive the scene as being at the scale you actually modeled it.

In 3D movies it is quite common to exaggerate the inter-axial separation so that people get more of the "3D" they are paying for, but if you do this in VR you are more likely to make the scene feel too small.

It shouldn't really depend on the headset because it's a property of the scene. However, because of the low resolution of current VR headsets it becomes difficult to perceive changes in depth beyond a few metres away (maybe 20 metres or so).

I wrote some more about it in this thread from 2016:

https://planetside.co.uk/forums/index.php?msg=225919

Just because milk is white doesn't mean that clouds are made of milk.

Hetzen

October 06, 2019, 05:02:47 pm #12 Last Edit: October 06, 2019, 05:16:41 pm by Hetzen
As Matt says it's up to how the scene is made in the VR software.

I would go at least 8k by 4k per eye if you are mapping on spheres. Going off my dusty memory, I believe eyes have a 50 degree horizontal angle field of view, so dividing a 360 rotation by 50 gives you 7.2 and to get a 1:1 pixel res on that sphere, you need to multiply the resolution of one eyes screen by 7.2. In the case of Vive, each eyes screen is 1080 x 1200.

1080 x 7.2 = 7,776‬ which is about an 8k by 4k image per eye.

*Edit: Just looked up eyes tend to have 60 degrees field of view, so those number can be a little lower. That said 8k by 4k will cover most things.

Matt

October 06, 2019, 06:19:56 pm #13 Last Edit: October 06, 2019, 06:44:42 pm by Matt
I think what's important is how the image is mapped onto the display, so it depends on the FOV of the display, not the eyes.

In my experience, for the original Vive you only need about 4k horizontal resolution for a 360 degree image, but I assume that more recent hardware could benefit from more than that.
Just because milk is white doesn't mean that clouds are made of milk.

Hetzen

October 06, 2019, 11:42:22 pm #14 Last Edit: October 06, 2019, 11:46:57 pm by Hetzen
That makes sense. I was told they were using a 50 degree camera, so that would be why.

As for the horizontal resolution, I've rendered out 4k by 2k animations for skyglobes on a few jobs now, which have been acceptable, especially as there's movement, but they weren't as good as 8k by 4k, especially if you only need a still, which is what Ulco needs.