We are creating a game that will be using 3 monitors two of which will have the same resolution, but the third will be a non standard resolution. Can UE4 output different cameras to each monitor and also support non-standard resolutions?
yup.
/end of answer
You should be able to pull this off using borderless window mode and opening multiple windows with their own GameViewportClients in them. This isnāt something we really test very often, but youāll probably notice that the Unreal Editor itself supports any combination of monitors, and it is presented using the same rendering system as a game uses. You may need to write a bit of custom code, but there should be no inherent technical limitation that would prevent you from setting up your product this way.
āMike
Is there any documentation on this? We need our game to span three displays, and itād be great to know where to access āborderless window mode and opening multiple windows with their own GameViewportClients in themā.
There is no documentation, and itās not a āsupportedā feature out of the box. But I think you should be able to get it working with a bit of engine changes. Take a look at the code in UGameEngine::Init(), specifically the calls to CreateGameWindow() and CreateGameViewport() to start.
A much more simple solution would be to span all monitors with a single borderless window, but youāll want the monitor displays to have the same resolution and a predictable arrangement for that to look right. You can try that out by simply starting in borderless mode and programmatically resizing your window across the desktop work area.
āMike
Thanks for your response, Mike. I forgot to subscribe to replies so I didnāt see it until now. If we are trying to create an immersive perspective with three different camera views for each of the three displays, would I also change that in GameViewportsClients? Can I have a single borderless window that spans all three and split it into thirds, one third for each camera view, and if so, can it be achieved without having to add three players to the SplitScreenInfo since this will only be one playerās overall view?
This type of documentation and support would be very useful for teams and individuals looking to use UE4 for immersive environments such as a CAVE.
Iām sorry to resurrect this thread but Iām also very interested in multiple viewports/monitors setup.
Did anyone get a link to a structured tutorial or walkthrough? Iāve found very fragmented, prob outdated, info about this subject and Iām about to start a project that would demand this kind of setupā¦
Thanks
We still have no official documentation on these features or code examples yet. We just strongly suspect that it is all possible to get working. 
You might try asking on the forums to see if anyone else has been brave enough to attempt a multi-device/viewport setup like this.
āMike
Thanks, Mike, Iāll try that later then.
Adding the link for the relevant thread in the forums:
UE4 forum thread
Better native support would be great to support devices like smartglass and WiiU controller and the playstation thing too.
And why not have it also for PC, one monitor can be used for items/menus/stats/maps (to make the rendering not too heavy)
Also touch screens are becoming more popular, so they are perfect to imitate the consoles functionality.
Better native support would be great to support devices like smartglass and WiiU controller and the playstation thing too.
And why not have it also for PC, one monitor can be used for items/menus/stats/maps (to make the rendering not too heavy)
Also touch screens are becoming more popular, so they are perfect to imitate the consoles functionality.
Also very interested in this as our client that we are working with wants the information-system one one screen and the ai and interaction on the other. Borderless window works but a way to determine this directly in the editor would make it hell of a lot easier to work with, since itās modular and works with any set of two screens.
Not saying it is the best way but the path of the least resistance for us was to run the main application as a server and everything else as clients. Specific pawns were used for the āsatelliteā apps, assigned based on the connection order. Other words, for each separate view/screen etc. we are running another UE4 application. They can be run on the same machine or different machines as long as theyāre networked and you have enough bandwidth.
Been looking further into this and I too came to the conclusion that this would probably be the āpath of the least resistanceā as you so eloquently put it
It does come with its own set of problems for us, making it hard if not impossible to use for our project though, bandwidth being one 
@acallado are you modifying engine .ini files for each satellite app to get it to go full screen borderless on the desired monitor? Or do you manually place them after launching?
I either did it through a .bat file or .ini file (itās been a while, sorry).
Maybe like this? How to - FULLSCREEN - packaged build? - Platform & Builds - Unreal Engine Forums
Maybe youāll want to use this until there is official engine support: GitHub - chaosgrid/ExtraCamWindow: A simple Unreal Engine 4 plugin that allows to have extra game windows with their own camera viewpoints.
Hey chaosgrid, I know this is months old but: I tried downloading your plugin and using it with 4.12.5 and it says that files are missing/doesnāt work. Does the pluggin still work?
I am using it with 4.16, It works fine.
Please try compile in the desired version of the UE4
I made some plugin, maybe it can help you GitHub - Batname/SpectatorWindow
