The Importance of Pixel Density and Retinal Resolution for AR/VR Headsets

Megalith

Megalith

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Anyone who has tried out AR or VR and has experienced the screen-door effect could probably tell you why density and resolution matters, but here is a piece that tries to be a wee bit more technical about the shortcomings of current headsets and what it would take to trick the eye into thinking it is seeing a real, live image. Thanks to Kyle for this one.

While most of us are used to dealing with resolution figures that describe pixel count (i.e.: a 1920×1080 monitor), pixel density stated as pixels per degree is a much more useful figure, especially when dealing with AR and VR headsets. Achieving “Retinal resolution” is the ultimate goal for headsets, where at a certain pixel density, even people with perfect vision can’t discern any additional detail.
 
I'm anxiously awaiting the next gen headsets... It's part of the reason I fully support all these 8k panels coming out. Pixel density is going to be a wonderful wonderful thing for small displays and VR/AR applications.
 
The hard part about this is that the content also needs to match the pixel density and some of the movies I've been able to find for my oculus are only 1080p. I guess it's not that big of a deal because I usually just watch the first 5 minutes and then skip to the end anyways but I'm sure some people who watch the whole thing would appreciate a matched resolution.
 
Seventyfive said:
The hard part about this is that the content also needs to match the pixel density and some of the movies I've been able to find for my oculus are only 1080p. I guess it's not that big of a deal because I usually just watch the first 5 minutes and then skip to the end anyways but I'm sure some people who watch the whole thing would appreciate a matched resolution.
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I've never heard of such a thing? Skipping the entire movie to watch the end? I personally don't mind if someone lays out the plot or tells me the ending to a movie/book, I feel it's better to know and see if you are interested before jumping in. But man, 5 minutes and bounce to the end? Odd to me
 
Due to the way most lenses work, the pixels per degree are not uniform across the entire display area when viewed. This can be OK though, so long as the user keeps their eyes mostly focused in the center. I am curious how added eye tracking might increase the area where high pixels per degree are required in the center.
 
Mugato said:
I've never heard of such a thing? Skipping the entire movie to watch the end? I personally don't mind if someone lays out the plot or tells me the ending to a movie/book, I feel it's better to know and see if you are interested before jumping in. But man, 5 minutes and bounce to the end? Odd to me
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Lmao...

You're not thinking the same movies I think he's watching.
 
Pixel Density and Retinal Resolution bla bla bla

This just in...more dpi(ppi) = better VR experience


(all they have to do is tilt or rotate the display a few degrees to greatly reduce the visible gap between each pixel)
 
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Mugato said:
I've never heard of such a thing? Skipping the entire movie to watch the end? I personally don't mind if someone lays out the plot or tells me the ending to a movie/book, I feel it's better to know and see if you are interested before jumping in. But man, 5 minutes and bounce to the end? Odd to me
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I agree. I sometimes do want to know if the plumber fixed that broken dishwasher before being distracted by the hot unhappy trophy housewife. It's these details I must not skip!
 
if Pimax can do it now, then why not wait for Oculus/Vive to do the same with likely better overall results?
 
Loose Nut said:
Pixel Density and Retinal Resolution bla bla bla

This just in...more dpi(ppi) = better VR experience
Click to expand...
Yep. Yet another "why isn't Gen2 here already" We should just have Gen2 4K here NAO" article followed by the predictable chorus of "waiting for Jen2" muppets that don't grasp 1) VR has to crawl before walk, and 2) the newest most powerful GPU's can only just now finally drive current gen HMD's at acceptable framerates and frametimes - a fringe of a fringe. Thus it's not display tech holding Gen2 back, but everything else.
 
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So we need 4K per eye? We're almost there. Of course, you need a pair of GTX 1080s or better. But that means that there'll be a single-GPU solution in 2 video card generations (3 years) and it will be mainstream in 4 (6 years).
 
There are a few companies trying to put out 4k per eye with a 210 degree FOV running off a single USB-C.
 
Quartz-1 said:
So we need 4K per eye? We're almost there. Of course, you need a pair of GTX 1080s or better. But that means that there'll be a single-GPU solution in 2 video card generations (3 years) and it will be mainstream in 4 (6 years).
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I imagine upscaling an image would reduce the screen door effect while not requiring the horsepower of a true dual 4k load. Look at the 4k enhanced projectors on the market. I realize it's not the same animal, but the concept could be applied similarly I would think.
 
This is where integrated eye-tracking will greatly help. Being able to track where the eye is looking and render that small section at full resolution, leaving the other 75% of the screen to render at quarter resolution. Essentially, the eye-trackers can trace where someone is looking in something insane like 4Ms, while that is happening, the GPU is rendering the full scene at half-resolution, once the eye tracking is done for the current frame, the GPU then renders the small region of the scene in the player's focus again, only at full-resolution.

Imagine 2160p -per eye (the ideal "good enough" resolution for VR ): Essentially, this reduces rendering costs by 2x, allowing the engine to render the each eye at 1920x1920 upscaled across the whole 2160x2160, and then ONLY render the small 25% of the in-focus area at annother 1080 x1080 fitted to the display's native resolution. This means the GPU only renders the equivilent of 2160x1080, potentially doubling the efficiency of the output.
 
^ Yes to eye-tracked foveated rendering... your periphery doesn't need to be high res at all... just concentrate on what the corner of your eye sees, it's like 144p maybe
 
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