The desktop side of UE4 uses a deferred rendering path which is why there is no support for MSAA there. Since UE4 mobile uses a separate forward rendering path, is it possible to use MSAA on iOS?
The only Anti-Aliasing available for Mobiles at the moment is temporal. There’s a small section in the documentation on it. I’ve tried a few anti-aliasing methods on iOS and none of them did anything. I didn’t notice much of a difference when using temporal either. You can find a small bit on available AA for mobiles under the Misc section here:
Hey guys, Metal supports MSAA as of 4.3 using the r.MobileMSAA cvar.
We have in our to-do to add support for Android & iOS GL.
Since the two answers contradict each other, and this is the third google results when searching for “ue4 iOS anti-aliasing”, I would like to report the results of my tests. I was not able to turn on Temporal anti-aliasing on iOS devices, no matter enabling metal forward rendering or not. I was instead able to enable MobileMSAA by modifying the BaseDeviceProfiles.ini files found in the engine folder (UnrealEngine/4.8/Engine/Config), under the [IOS Device Profile] section, in the following way:
// Temporal AA (?) looks blurry right now
//+CVars=r.PostProcessAAQuality=0
// Not sure on this one - may need the whole D Buffer stuff going
+CVars=r.Decal.StencilSizeThreshold=-1
// mobile MSAA
+CVars=r.MobileMSAA=1
i.e., commenting out the +CVars=r.PostProcessAAQuality=0 line, and adding the last line. I haven’t tried with values greater than 1, but I noticed that, this way, MSAA was on when running on metal-enabled devices (didn’t try with older iOS devices, since I don’t have them at disposal) regardless that “forward rendering with metal” was enabled or not.