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[Screendoor effect] pentile vs rgb

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[Screendoor effect] pentile vs rgb

Postby Tgaud » Wed Aug 07, 2013 5:14 am

Hello,

do you think a pentile display (like samsung oled) would make the screendoor effect look better than the RGB one ?
At first we can think that like there is less subpixel in pentile, the subpixel would be bigger.
But.. like the subpixel have a whole different shape and color than RGB, maybe it helps removing the "grid" effect, with something a little more blurry.

In pentile the pixel matrix seem harder to perceive there is less this "grid" effect i think.

Galaxy note 2 use strip Rgb
Gs3 use RGBG pentile
Gs4 use pentile diamond matrix

Image
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Re: pentile vs rgb

Postby geekmaster » Wed Aug 07, 2013 5:39 am

Considering that the Rift magnifies the display large enough to see individual pixels (the primary source of the screendoor effect), until PenTile displays are available at MUCH higher resolution, such displays would be a horrible compromise over the current RGB subpixel displays:
http://www.phonedog.com/2011/08/02/should-you-avoid-smartphones-with-pentile-displays/ wrote:... I do not consider myself a display buff or expert by any stretch of the terms; as long as the display I'm using is decently clear and brightness is sustainable, I'm probably not going to care too much one way or the other. But one aspect of smartphone displays that has really me grabbed my attention lately lies within the subpixel layout, particularly of the PenTile Matrix family. ... Even though the qHD display found on the DROID 3 is technically a higher resolution, this particular display shows more pixelation and grain than that of a standard resolution display (i.e.: EVO 4G, DROID X, Nexus S, etc.), thanks to the PenTile subpixel layout. ... If you pay close attention to these displays, you will begin to see the checkerboarding effect in areas of high contrast or high saturation. ... PenTile displays are not all bad; they actually come with several advantages over competing technology. For instance, your standard RGB stripe is just that, a stripe with red, green and blue subpixels to each pixel. PenTile technology uses 33 percent fewer subpixels (two per pixel) and adds a white subpixel that gives the image added brightness and can aid the display in brighter or whiter color reproduction. ... Nouvoyance, the creators of PenTile, also explains that with their technology, "'pixels' in the traditional sense have been eliminated in PenTile RGBW™ displays; individual subpixels are not restricted to use in one pixel group, but instead participate in multiple 'logical' pixels in their surrounding vicinity." ... If you can look at a PenTile display and not see the checkerboarding or pixelation, or you want something with a little extra battery life, a phone with a PenTile display will suit you well. Personally, I take one glance at the display and I can see checkerboarding from an arm's length. The more I use a PenTile display, the more I see pixelation and the more it messes with my eyes. PenTile is not all it's cracked up to be by Nouvoyance and it's not as bad as some people make it seem. It's a good middle-of-the-road display with a few benefits of its own.

A similar conclusion from a (perhaps) more authoritative source:
http://www.androidauthority.com/samsung-galaxy-s3-pentile-display-reliable-84716/ wrote:PenTile displays are perceived as brighter than RGB screens, but many display purists consider them fuzzier and overall inferior to the classic RGB.

PenTile needs much higher resolution than RGB for acceptable image quality, but fails in image quality tests when compared to an RGB display of the same resolution. Magnification used in an HMD will only make the PenTile visual artifacts much more of an annoyance than when used on a hand-held device.

By the time PenTile displays have enough resolution to overcome the ugly visible artifacts (different from screendoor effect, but much worse according to people who care about visual display quality), standard RGB displays will also have much higher resolution, and perhaps much sooner.

The main benefit of PenTile displays is lower power consumption and longer lifetime (for portable applications), not display quality (at a comparable resolution).

When the display resolution gets high enough, subpixel layout will no longer be important, at which time the low power and long lifetime benefits of PenTile may win out over RGB. But until then, RGB is considered to provide better image quality.

Also, due to the "distributed subpixels" and "not real pixels" layout, there are disputes about resolution claims of PenTile displays not really being high resolution as claimed in their marketing specifications. Distributed subpixels would certainly contribute to that perceived "fuzzy" appearance people talk about.

If you want fuzzy instead of screendoor, you could put a diffusion filter over your LCD display. This was attempted in various threads, but in general, even the best solutions were eventually discarded in favor of a "naked" LCD panel (just as Palmer Luckey had done in the past with early pre-Rift prototypes). I think PenTile will be a lot like a diffusion filter over RGB, where people who try it will want the higher visual quality of standard RGB sub-pixel displays. This may change when we get 8K displays for our HMDs, but for now, PenTile may not be a viable option for an HMD like the Consumer Rift.
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Re: [Screendoor effect] pentile vs rgb

Postby Tgaud » Wed Aug 07, 2013 7:09 am

I'm aggree with you on the less subpixel thing.
So the pixels shoud be "more visible".

But what i'm thinking is that he problem isn't so much the "pixel being visible" than the "GRID" aspect, with lines.

I'm agree with you that on a RGB the pixel will be less visible than pentile.
But as long as we already see the pixels... two other aspects have to come into consideration :
What do we see exactly, what kind of do we perceive ?



I want to have two axes of reflection, before taking my definite conclusion :

1) About the colors.
The screendoor effect is annoying not only because we can see pixel, but also because the visible pixels have a lot of color contrast beetween each other. so we really see individual dots.

Some Pentile, sometimes use white pixels.
If we're already in a situation where we can see the pixels even in RGB.
Don't you think that "white" pixel, would be less terrible to look, in opposition to high contrast RGB subpixel?
A white pixel (in the philosophy of pentile) is already a kind of "melted" subpixel
Where it got critizided cuz there is less information and its a little more blurry... Its maybe what we want in this scenario, having something giving the correct perceived color information (pentile philosophy) without looking like high color contrast Red, green, blue dots


2) About the shape.
the screendoor effect is really annoying not only because we can see the pixels... but because of the GRID effect.
vertical/horizontal line everywhere.
Maybe the new pentile shape, and different subpixel Size could help killing this grid Effect.
We would effectively still see the subpixel, but if we choose the Diamond matrix there is not more such things as "lines".
So there is "Dots" yes, but not the "grid" aspect anymore.


I hope i explain good, cuz i always have some trouble to communicate ideas in another language, in such technicals discussions.





But pentiles style are numerous... so there is a lot of situation to inspect.
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Re: [Screendoor effect] pentile vs rgb

Postby Tgaud » Thu Aug 08, 2013 8:29 am

I hope to have you opinion on this
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Re: [Screendoor effect] pentile vs rgb

Postby geekmaster » Fri Aug 09, 2013 6:35 am

I just did an interesting experiment related to this last night. I rendered scenes to a checkerboard pattern, replacing "red" pixels with my images. I left all the "black" pixels black. When viewing video content on this, the "screendoor" becomes diagonal instead of being a grid of vertical and horizontal lines. Even though I only used half as many pixels, this made the perceived screendoor effect mostly go away. This was actually a side effect of changes I made to the "Mountains" shadertoy to make it work well on my Rift with SBS partial overlap (which is awesome, BTW). I spent too much time viewing that in my Rift. Next, to add head tracking. I did NOT use pre-warp, and like others have posted, that seems somehow to not cause motion sickness... Somehow that seems counter-intuitive. EDIT: I just changed the cameras to be about 10,000x closer together. Now the mountains and trees look MUCH larger, and it did make me dizzy. Perhaps my morning coffee contributed to perceived motion sickness?

Now here is why this checkerboard experiment is useful to this thread:

My eyes seem more as perceptive of of lines that are near horizontal and near vertical. This was also a reason why the XO/OLPC displays (later Pixel Qi) use a diagonal pixel grid. The perceived resolution seems higher when pixel boundaries are not aligned parallel or perpendicular to the horizon.

I also implemented checkerboard interlaced rendering many months ago (before I even got my Rift) in an effort to increase framebuffer rendering speed. I also noticed how it seemed to lessen perceived screendoor effect back then too (although only when the view is rotating). During a stationary view pixels do not change and screendoor is again visible.

PenTile also uses a different grid, which may help remove screendoor effect to some extent, but as mentioned earlier it needs much higher resolution to overcome annoying visible artifacts of its own.
Last edited by geekmaster on Fri Aug 09, 2013 8:21 am, edited 1 time in total.
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Re: [Screendoor effect] pentile vs rgb

Postby Tgaud » Fri Aug 09, 2013 6:47 am

what I like about the pentile GS4 diamond
Is that there is NO dark line.
neither vertical, horizontal, diagonal..
So there is absolutly no way to see a grid.

I know there still will be "something" undefined, lack or resolution, but I dont know how much impact it would have
on this "screen door effect" and how much degradation it woud cause.

If benefits would be higher than problems.
I think it would, by far.. but i have no way to test or proove that.
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Re: [Screendoor effect] pentile vs rgb

Postby geekmaster » Fri Aug 09, 2013 7:05 am

Tgaud wrote:what I like about the pentile GS4 diamond
Is that there is NO dark line.
neither vertical, horizontal, diagonal..
So there is absolutly no way to see a grid.

I know there still will be "something" undefined, lack or resolution, but I dont know how much impact it would have
on this "screen door effect" and how much degradation it woud cause.

If benefits would be higher than problems.
I think it would, by far.. but i have no way to test or proove that.

Like most things, things in practice are often not as predicted in theory. The only way to fairly evaluate different display technologies is in a side-by-side comparison, and statistically evaluated by a large number of people due to subjective preferences. There are already people who love PenTile in smartphones, and others who dislike it. This "rift" in differences of opinion will only be magnified by HMD lenses.
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Re: [Screendoor effect] pentile vs rgb

Postby atavener » Fri Aug 09, 2013 1:29 pm

This all reminds me of a time long ago when I was toying with the idea of my own game-system. I was designing the video system to address/signal individial pels (we now refer to as subpixels) in a hexagonal array, because that's what I thought TVs (CRT) used -- I thought the shadow mask was a hex grid (actually circles). I think that was even older TVs because I ended up finally looking at some TVs up close and most were |R|G|B|. This was disappointing because I was expecting the added apparent resolution would be great (I was miffed when cleartype was hailed as something miraculous!), as well as the narrower angle (60deg) between natural lines.

So, this kind of arrangement: (*Edit: fixing alignment)
..BRGBR
.RGBRGB
..BRGBR

And now I can't even find reference to it. Except hinted at in some patents referring to a shadow-mask of hexagonal type.
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Re: [Screendoor effect] pentile vs rgb

Postby guspaz » Fri Aug 09, 2013 3:07 pm

All of the subpixel arrangements you showed in your first post would produce a noticeable screendoor effect. The screendoor effect does not just come from dead space between pixels, but from the different brightness (either perceived or actual) of different colours of light.

For example, the Rift display today has effectively no dead space between subpixels on the horizontal axis, and a large amount of deadspace between pixels on the vertical axis. You might think that this means that the screendoor effect should only be visible in one direction, where the black gap is. But when you use the thing, you actually see it on both axes. This is because the green subpixel seems much brighter than the red or (most of all) the blue. So your eye interprets that difference in brightness as a gap, and you end up with a full 2D grid screendoor effect.

In the particular RGB arrangement of the SGN2, you'll perceive a 2D grid screendoor effect (even looking at the macro picture you can) because the green is spaced out and much brighter than the red or blue. In the RGBG pentile arrangement on the SGS3, you'll see a primarily vertical screendoor effect (between vertical columns) because the green pixels are all lined up and largely touching, but are thinner and much brighter than the red/blue beside it. In the SGS4, the diamond pentile arrangement would produce an effect similar to the SGN2, where the grid of green pixels is primarily visible, leading to a perceived 2D grid screendoor.

There isn't really any possible subpixel arrangement that would completely eliminate the screendoor effect. Using a panel with minimal dead space would help, but the only real solution is to increase the panel resolution. A diffuser might help, but that's tricky to get just right. Besides, in my experience, the screen-door effect isn't nearly so distracting as the super low resolution producing a super low detail image.
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Re: [Screendoor effect] pentile vs rgb

Postby Tgaud » Fri Aug 09, 2013 4:27 pm

I'm not agree with your statement.

If what you say is true, (one some screen one subpixel is brigther than the other) It would meant that the perceived color would be false.

You can't disassociate : subpixel brithness / eye sensibility to each color(different for each) / size of each subpixel according th his color.

they play with shape and brigtness to get the screen have more longetivity. but in any case the final perceived pixel color effect is the same.

Yo do have space beetween pixel, and its indeed what you perceive.
IF what you say were true, we would see a screendoor difference when looking a whole blue/red/green image (even when the subpixel color you name are off) , but there is not. The screen door is always present in sames circonstances.
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Re: [Screendoor effect] pentile vs rgb

Postby kojack » Sat Aug 10, 2013 1:07 am

Tgaud wrote:Yo do have space beetween pixel, and its indeed what you perceive.


As I've posted before on here, this is a photo I took of the rift panel (direct shot of the screen, not through a rift lens). There is not enough space between pixels horizontally to be noticeable.

Image


I just tried looking at my Galaxy Note 2 using a rift lens. The screen door effect is still there. Not as bad as the rift, but still visible.
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Re: [Screendoor effect] pentile vs rgb

Postby Tgaud » Sat Aug 10, 2013 3:16 am

thats obvious, because the galaxy note 2 is NOT pentile. ;)
only the galaxy S serie is pentile.

And my observation is even more focus on the diamond matrix
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Re: [Screendoor effect] pentile vs rgb

Postby kojack » Sat Aug 10, 2013 4:48 am

Good point.
(It's still a different arrangement to the rift panel)
Although it's not just the S series. The first Galaxy Note was RGBG pentile.

On my Galaxy S (which I now use as just an alarm clock)... urgh. I think I prefer the screen door effect.
With higher res it's probably ok, but at the current res (which is still higher ppi than the rift, 233ppi vs 215) areas of white become a checkerboard of red and black (really blue, but looks black), with faint thin green strips. The red pixels are very dominant. It needs much more than 233ppi to make the pixels mix.
I might bring a rift lens to work on monday and ask if any of my students have a galaxy s3 (306ppi).
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Re: [Screendoor effect] pentile vs rgb

Postby Tgaud » Sat Aug 10, 2013 1:40 pm

yeah but galaxy S1 was using "white" subpixel. it was a strange pentile actualy...
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Re: [Screendoor effect] pentile vs rgb

Postby kojack » Sat Aug 10, 2013 7:10 pm

Tgaud wrote:yeah but galaxy S1 was using "white" subpixel. it was a strange pentile actualy...

Looks similar to your S3 pic except with slightly larger blue sub pixels.
Wikipedia lists only 4 motorola phones as using white subpixel RGBW pentile.

This is my S1 through a macro lens:
Image
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Re: [Screendoor effect] pentile vs rgb

Postby Tgaud » Sun Aug 11, 2013 4:05 am

As long as we can see black "line" in the macro, it's obvious for me that we will have a grid effect.
I really wonder how it would look like with a diamond matrix
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Re: [Screendoor effect] pentile vs rgb

Postby mirak » Mon Nov 25, 2013 6:40 am

Tgaud wrote:thats obvious, because the galaxy note 2 is NOT pentile. ;)
only the galaxy S serie is pentile.

And my observation is even more focus on the diamond matrix


The Galaxy Note 2 is Pentile.
Only the Galaxy S2 is not Pentile.
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Re: [Screendoor effect] pentile vs rgb

Postby TWhite » Mon Nov 25, 2013 1:42 pm

mirak wrote:
Tgaud wrote:thats obvious, because the galaxy note 2 is NOT pentile. ;)
only the galaxy S serie is pentile.

And my observation is even more focus on the diamond matrix


The Galaxy Note 2 is Pentile.
Only the Galaxy S2 is not Pentile.


False. The GN2 is indeed an rgb arrangement however it is not a stripe. It is still not pentile. There are 3 subpixels to every single array element in the note 2's display. This is specifically why I went with this phone over the s3 or even s4. The 720p amoled screen on the note 2 is without artifacts and is the last good display Samsung has used on a phone.
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Re: [Screendoor effect] pentile vs rgb

Postby mirak » Mon Nov 25, 2013 2:01 pm

TWhite wrote:
mirak wrote:
Tgaud wrote:thats obvious, because the galaxy note 2 is NOT pentile. ;)
only the galaxy S serie is pentile.

And my observation is even more focus on the diamond matrix


The Galaxy Note 2 is Pentile.
Only the Galaxy S2 is not Pentile.


False. The GN2 is indeed an rgb arrangement however it is not a stripe. It is still not pentile. There are 3 subpixels to every single array element in the note 2's display. This is specifically why I went with this phone over the s3 or even s4. The 720p amoled screen on the note 2 is without artifacts and is the last good display Samsung has used on a phone.

I really was thinking about GN 1 when reading GN2, probably because it came out at the same time than GS2.
But yes only GS2 and GN2 are not pentile.
Unfortunely.
I would prefer Samsung not pretend to have HD FullHD and a lower resolution without pentile.

This is why I stuck so long to the GS2 and also because I wanted the padfone, and I have the padfone inifinity a86 now
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