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NTHUSIM • View topic - Is custom resolution/aspect ratio possible ?

Is custom resolution/aspect ratio possible ?

Your projector questions can be answered here.

Postby Guest » Sun Sep 07, 2014 6:03 am


I'm in the process of creating my own immersive screen (currently preparing a dedicated room and trying to figure out the projection setup which is driving me mad...).

My goal is to achieve a physical 58° V Fov for 143° H FoV.
58° V is chosen because it is the "standard" for most games and 143° H because it is a reasonably wide (for anything other than sims) and match a 3x1 16/9 based setup.

the room is 12 feets wide so max radius is 6 feets provided that I would be at dead center the height of the screen should be around 6.5 feets to achieve the 58° V.

In order to fill this with projectors and still have a decent quality (pixel size vs view distance) I think the best option is a 3x2 (1080p based) cylindrical setup but the screen ratio would not lead to a 143° H.

So the question is: Is it possible to configure a custom "big screen" resolution different from the actual projector configuration
make the game believe that the virtual screen is like a 3x1 FHD setup: 5760x1080 which would render the desired 58° V Fov for 143° H FoV.
and wrap/scale this to a 3x2 FHD projector setup: 5760x2160 that could physically match the rendered 58/143°.

note that 5760x1080 rendering is just an exemple the idea is that we could use bigger resolution and downscale to physical or smaller resolution and upscale as long as we use the appropriate aspect ratio leading to the desired H Fov knowing that in most case the V FoV is fixed and 58°.

also any other idea to (nearly) achieve this goal is welcome...

Postby BHawthorne » Sun Sep 07, 2014 11:34 am

One thing of note, Nthusim Plus only does single, dual or triple projector.

AMD is notoriously difficult in making custom resolutions. This is one of the few things I like Nvidia better for.

By your spanning designation 3x2, my assumption is that you're using Eyefinity. I could speak with Andy and see if we could accommodate you with Immersaview Warp in order to do 3x2 at the cost of Nthusim Plus. If customers want to do something non-commercial outside the scope of Nthusim capability Immersaview reviews the request on a case by case basis for use of Immersaview Warp.
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Postby Guest » Sun Sep 07, 2014 8:43 pm


Postby BHawthorne » Mon Sep 08, 2014 12:05 pm

No worries, I'm here to help people learn from my previous experiences -- both the good and the bad. :)

That pic is my 2013 screen build. It is using two Optoma GT720, which are 1280x800 short throw projectors with a lens throw of 0.72:1. I believe they EOL'ed the GT720 in 2011 and are already up to the GT760 now (which I believe is a 0.52:1 short throw). I think Optoma also came out with a GT1080 now, which is their first GameTime series projector that is 1920x1080. I also like the BenQ W1080ST. For the longest time, the W1080ST was the only 1080p short throw on the market. So, it was pretty much the only option in town if you wanted to go 1920x1080. With the GT1080 out now it might also be a good contender for options. The thing about the GT1080 is I don't know of anyone who has one yet.

The problem with the GT760, GT1080 and W1080ST is they're all UHP bulb based. That means the old traditional 3500-5000 hour bulb life and they run hot. 3 of those in a room can raise the temperature in the room. Which brings me to another alternative -- Laser-LED bulb based projectors. They run cool and have long bulb life -- 20,000 hours+. And since they run cool you could do something exotic with them. Run them in portrait mode -- Eyefinity 5x1P if you wanted to go a bit crazy in design. Of the Laser-LED bulb projectors I'd suggest the Optoma ZW212ST. It's a bright projector and it runs cool. Just throwing out there some ideas to let your imagination wander a bit. *grin*

GT760: http://www.optomausa.com/products/detail/GT760
GT1080: http://www.optomausa.com/products/detail/GT1080
ZW212ST: http://www.optomausa.com/products/detail/ZW212ST
W1080ST: http://www.benq.us/product/projector/W1080ST

Given that setup in the picture, I still would recommend 1080p projectors over that setup. Sure, you can read the fonts but I really don't like the pixel size on that. Anti-aliasing is hiding some of the ugliness of the pixel size in that photo.
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Postby Guest » Tue Sep 09, 2014 7:19 am

I have already considered the possibility of a 5x1 setup but rejected the idea due to:
- difficulty to mount (and fine tune) 5 projector in this position.
- difficulty to find a suitable location, the usually limited (if any) horizontal lens shift means that they have to be at almost head level impossible in front of the user... not really better behind...
- they would also "fill" the back of the room which is the door side. Add to this the 4 of the full height speakers of a 7.1 surround sound setup in the vicinity... well not sure it still possible to reach the seat.
- portrait mode is yet an other thing that Gfx card seems to not handle so well when it comes to surround vision.
- there might be some moving parts not designed to have their axis in this position (I wonder if the DLP moving "mirrors" are concerned).
- Heat is an concern too and LED may help but 1: LED costs a lot it looks like you pay upfront for 10 years of the bulb replacement. 2: can't find any "good" led below the 3K$ segment. By good I means fast (input lag, blur) good image, good black, and very good shadow details (I have full control over the light in the room so I can help the black level and so I value more the shadow details over the black level). As I would need 5 to 6 of them even 2K$ is just too much. Anyway I don't want to sacrifice the image quality for a few bulb replacement...

I have a side question about the projectors. It seems that everybody want short throw pj but is there any other reason than the placement issue?
For me long throw means at least less focus issue, less lost pixel in the warping process and better light uniformity.

FYI My current (nothing definitive) short list of projector is:
Sony VPL-HW55ES in a 3 pj setup at most (those are not cheap... so 3 is a max)
Benq 1080ST in a 6 setup (placement forbids 1070 non ST here).

Here are the important questions that would help me sort the first step in the options:
- on a 1080p (dlp) projector seen at 6 feet are pixels and screen door effect clearly visible, barely visible, not at all visible... ?
- on a 1080p (dlp) projector seen at 6 feet and after some warp are the small texts like those in Rift chat box easily readable, barely readable, not readable...?

everything depends on the fact that 1080p is good enough and does not require to double the vertical resolution...

options for single row:
- 2x1: easy, least gfx power hungry and allow a good physical V Fov but 127° of rendered H Fov is just not enough to wrap on a 143-180° screen unless most games allows a custom FoV. Upgrade path: 2x UHD or 4K projector but in 3-4 years at least due gfx power required and pj price and availability.
- 3x1: easy, reasonable gfx power needed, a good rendered 143° but seems impossible to achieve a physical V FoV of anything near 58°, Upgrade path: same as 2x but even more power and cost...

options for two row:
-3x2: complex, high gfx power required (this is one and an half UHD. something like 2x Radeon R9 295x2 is mandatory), easy 58° V Fov, but even worse than 2x1 as far aspect ratio is concerned tuning the game FoV is mandatory. Upgrade: no need the image should be top quality (Pixel size vs view distance)... just upgrade the gfx card for better performance...

Just got an idea (ok probably it is not new but at least it is interesting for my issues) for a trick on a 2x1 setup: plug a third screen (any monitor with same resolution as the two projectors) add it to the 2x1 setup making it a 3x1 setup but wrap the rendered image on the two projectors only (leaving the monitor empty). This way we should be able to force the game to render a 3x1 view (so 143° FoV) and wrap this to a 2x1 setup which can easily match the 143° I think (the increased horizontal resolution may even improve the warp quality).
This trick doesn't rely on tricky features like gfx card scaling so that should be easy and reliable unless there are some limitations I'm not aware of.
You may even give it a try on your 2x1 setup (provided the setup is still in use and provided the trick has not already been tried ;) )
nb: Same would work on 3x2 but 6 additional fake monitor would be required and the amount of gfx power would be... well just insane.
nb: if the monitor has multiple input it can even be used to display something else by cabling it on two different port on both the monitor and the computer and use the second port to display for example a secondary screen as we don't need to actually display the first that only contains the non warped part.
nb: bonus benefit, being physically a 3x1 setup NVIDIA can be used.

What do you think about that trick ? if it works it means the 2x1 setup is the most interesting with both good rendered and physical FoV and also good price, upgradability and required gfx power.
It just need to be good enough to my taste. So please can you confirm the feasibility, can we trick NTHUSIM PLUS in to believing there is a third projector and can we warp the image on 2/3 of the believed total physical screen ?

I should mention I'm not in a hurry... full room preparation even if already started will require a few month before I buy projector/screen/wrapper my target is around the end of the year.

I'm curious about what's your current generic gaming setup (I say generic because it looks like you have more than one, some being very sim oriented).
And what's the setup you like the most (ideal ?) to play FPS, RPG, MMO, Racing...

Postby BHawthorne » Tue Sep 09, 2014 12:12 pm

Lots to digest and answer so I'll answer this over multiple paragraphs.

Agreed on 5x1P. The only reason to go 5x1P is to get that pixel height of 1280 or 1920 in portrait vs 800 or 1080 for landscape options. You're adding complexity to get better resolution. Then again, 3x2 is also adding complexity to get better resolution. My thought process is that 1920 is pretty much 2160 for the cost of one less projector. Either way, you're talking about a logistical headache to maintain calibration on 5 or 6 projectors with routine use. And as mentioned portrait mode does effect mounting design. Often portrait mode setups are done rear projection which is most likely not an option in your setup. The only reason to go LED-Laser hybrid is portrait mode. It's otherwise jsut cheaper to go with a UHP bulb design projector and landscape mode. It ends up being about the same over the span of the life of the projector for cost, but depends on if you want to pay for bulbs over time or on the front end.

The reason why people go short throw is that they tend to go wall size. Then they tend to put themselves in the middle of the radius of the screen design. Depending on the projector, the lens throw will put you in between the screen and the projector obscuring some of the projection. To avoid that, short throw projectors are ceiling mounted close to the screen. Often forward of where the user is seated or overhead of where he is seated. Long throw projectors put your shadow into the projection, which none wants. This can often be accounted for by mounting location though. A long throw could be mounted in a high ceiling room, allowing the projection never to be near the seated user. But that is not always an option, so short throws are preferable.

Screen door effect and pixel size. My first screen used LCD projectors way back in 2008. The screen door effect was horrendous. In 2009 I shifted over to my very first set of DLP projectors. You can see in my early YouTube videos those in use back in 2010. Those were 1024x768 Optoma EX525ST. They had some pretty blatant pixel size to them. I then changed to GT720's in 2011, which were about the same -- 768 vs 800 pixel height. In 2014 I've been using a BenQ W1070 for a home theater setup. I feel a bit better about the pixel size with it. It would be quite similar to the W1080ST, just different lens throw ratio. With pixel size and screen door effect, everything is a compromise. You're going to get some of it no matter what you do. DLP helps though as the black area between the pixels is minimized vs the old LCD projectors. But, we're still talking about the pixel size itself, so that is why I passively always talk about portrait mode. I like the idea of a 1920 pixel height vs a 1080. It's almost 2x the pixel density if set up right. But as you pointed out earlier there are issues with portrait mode.

2x1 is good for pushing high FPS, because it's not graphically intensive. But the flip side of that same coin, you're working with large pixels. Fonts are going to be problematic. If I do 2x1 again, it's at the very least going to be using W1080ST or GT1080. 800p is very borderline on pixel size. 3x1 is the old standby for all gaming setups for spanning modes. It'll be the most compatible with games. It's more pixels to push and adds a third projector to the cost. Benifit of 3x1 is the blends are not in your center FOV so when things get out of calibration via a projector getting bumped it not as annoying as 2x1 is.

3x2 gets logistically problematic for maintaining calibration. You're gaining resolution and pixel density, but trading off simplicity and simple maintenance. Plus it's going to require some serious horsepower -- like the R9 295X2's you mention. Personally, I think you'd get frustrated with 3x2 unless we used auto calibration method for the projectors. That is something new coming to Immersaview SimVisuals. Ed is working on that right now.

I look at everything as a compromise in one way or the other. It really depends on what you value most -- simplicity or pixel density, FPS speed or resolution, base cost vs large budget. Either way there is always going to be some facet in the setup that will be compromised a bit. It's just the nature of multi-projector. When you go big, often something in the design will suffer a bit -- be it FPS, budget or resolution. There is no singular right answer. Some answers are more right than others based on your preferences though.
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Postby Guest » Thu Sep 11, 2014 3:56 am

Could you confirm that the trick described above (3 screen connected but only two used for projector warp) works ?

I guess connecting is not an issue and nthusim should probably not put any restriction other than to have the same resolution on each screen but I wonder if Nthusim allows to move the warping control points so much that every control points expected to be on one screen ends up to be on the screen next to it (to warp a 3 screen wide sized image on 2/3 of the screen i.e. the two projector next to the monitor).

If yes I'll go for this setup as it seems to be the best solution and use the sony as its technology allows for no screen door at all and even less visible pixel than DLP.

Postby BHawthorne » Thu Sep 11, 2014 9:30 am

At issue is you'd need to edge butt the projection because if you enable edge blend but are only blending two displays but not the third it becomes an issue. The third display which doesn't need pre-warp would just have a default grid setting.
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