Someone on the Unity forums was asking how Unity 5 looks on a 5k Retina iMac. About a month ago I sold my 1 year old iMac and got the 5k. Here’s what I said about it on the forum:
I recently just swapped out my top of the line iMac with a near top of the line 5k iMac. Unity looks exactly the same on the new iMac as it did on the old one. I have my Display Preferences set to “default” for Resolution. This means that all the app detail, the text, the size of the window borders, etc, are all the same as if the monitor wasn’t retina. That opposed to everything being “tiny” as someone suggested it would be. You can switch your Resolution setting to “more space” and then everything does become tiny but I didn’t do that. My eyes are too old for that.
As for the GPU. I got the 2 Gig GPU instead of the 4 Gig GPU and I already regret it. In my opinion Apple didn’t beef up the GPU enough for the 5k. My GPU on my older iMac, I believe, was beefier. But it didn’t have Thunderbolt 2.0 and couldn’t support 4k. Otherwise I would have gone with a 4k external monitor and kept my main screen non-retina.
I haven’t had any performance problems inside of Unity though. The problems I had were inside of Substance Painter. There when painting on a 2k texture the system got very laggy. Unusably slow actually. So the moment Apple comes out with a better GPU on the 5k iMac I’ll probably be upgrading again.
One of the reasons I wanted to go 4k was because many of the devices that I develop for (iPad, iPhone 6+) are too large to emulate in the game window. The 750×1334 of the iPhone 6 is the largest I can go. And in the default display resolution setting this is unchanged. The Game window isn’t recognizing the 2.0 scale factor of the display and is probably rendering at a non-retina 1.0 scale factor. Which would mean that it’s rendering 750×1334 and displaying it in a window with double the width and height of that. Double that should support up to 1500×2668 – so hopefully Unity will eventually support the 2.0 retina thing and give you a scale option. IMHO they need to do that to help justify the extra $75 a month for iOS people.
To get to a full iPhone 6+ in the tall orientation you need to get to 1920 tall. Unfortunately even when you set the render to more space the biggest you can go is 1735 tall. So it doesn’t solve the iPhone 6+ preview problem. Testing for that resolution will have to remain on actual devices for now. 1920×1080 in the wide orientation does work though.