When you are exporting cubemap images from Spacescape 0.5 it now has a setting for PNG export specifically for Unreal. Unfortunately it does not work correctly.
But after a lot of trial and error (Holy hell the UE4 texture input is slow!) I got it working.
After importing into photoshop, assemble the frames in the order 1-6 left to right. Then:
- Rotate frame 1 90 degrees clockwise
- Rotate frame 2 90 degrees counterclockwise
- Rotate frame 3 180 degrees
Then export using the nvidia dds photoshop tools wait a bazzlion minutes for unreal to import it and you are good to go.
NOTE: I have submitted a bug to their site and it looks like it is pretty active so I would imagine it will get fixed soon but if you don’t want to wait try the above things.