Click the show button in your perspective viewport and select “Use Defaults” just to make sure everything is kosher on your end.
Project was fine last time I opened it (week ago or so). Today I opened it and got surprised - I don’t know how to describe, so please check video:
And this is how it looks when engine works fine:Vineyard - Bekerman Challenge on Vimeo (it was done around week ago, last time I opened project without problems)
You can see wireframe is perfectly fine (except for some reason the wireframe of one of few Landscape in background overlaps on top front objects wireframes) but when I switch to Unlit or Lit, or Play, it becomes unreadable/extremely artifacted (or stretched).
Points to mind :
- no changes we’re done on my part as far as I know (including modifying project settings or project files).
- no video card drivers update.
- no updates on engine (it was working fine on newest 4.8 version, 4.8.3)
- it’s not camera settings issue - wireframe is fine. Problem occurs in Unlit/Lit/Play, so pretty much anywhere shading is
- disabling any fog/post process layers doesn’t help
- opening other levels shows the same problem
I can send needed project file, via uploading archived files into my ftp.
I’m clueless what could cause such strange look and can’t think of any possibles changes I could do after last successful project open. With one exception - I’ve updated today 4.9 engine from 4.9.1 to 4.9.2, but I’m opening the problematic project in 4.8.3. No conversion. Not sure if it’s related, but that’s only one thing I can think of.
Did that, no change 
Did few things, no solution yet. Uninstalled 4.9.2, no luck. Then opened another level in the same project. Unlit mode kinda is ok, except camera has problems with depth - some elements that are behind, are overlapping front elements. The scene is really simple (new level, default), no cameras or fog/pp layers. But when I switch to Lit mode, you can see the warp effect into some single point. This single point is fixed, independent from my view position. I think the point might be 0,0,0 gizmo of world.
I’ve opened other project and it was fine. I’m fearing that my problematic project got corrupted (could be 4.8 version get corrupted when UE4 was copying 4.8 to 4.9?) 
Oh, I’ve noticed just now - check the icons (of player start, light, sky light etc) - they’re flattened horizontally, instead facing the camera.
Found culprit, however I don’t understand what exactly caused this extreme warp effect. It’s DefaultEngine.ini file from project’s Config folder. When you rename it/move/delete, project works fine. But it’s a huge file and I don’t know which parameter is fault.
I’d be glad to provide needed materials if anyone from Epic wants to investigate.
Cheers! Was lucky with this find!