I’ve just upgraded to UE v4.7.3. After applying a few tweaks to my project blueprints and having it converted over, I decided to try out the new “VR Preview” function.
It works for the Oculus Rift DK2 so long as you’ve upgraded the Oculus Config Utility’s Runtime to their 0.4.4 version.
However, the FPS decreases in Preview mode versus when running as a Stand-alone game in the Rift. I have been getting best case 75FPS when running as a Stand-alone game in the Rift versus best case 60FPS in VR Preview.
Another developer also mentioned the same phenomenon in a separate thread for a different problem (VR Preview not available in 4.7 - XR Development - Epic Developer Community Forums).
If this is a known issue, please keep me abreast of any developments/updates to getting it fixed. Otherwise, can you create a bug report and have it looked into? Hopefully, there will be a fix as “VR Preview” is rather convenient and quicker to start up then running as a Stand-alone.