So I am working on a little Rift demo. Turning off “hmd vsync” gives me 85-100 fps in the Rift, but I kept noticing that it didn’t feel quite right. I added “hmd lp on” which helped some, but it still didn’t feel super smooth. Not as smooth as you would expect at least. I turned HMD Vsync back ON, and FPS is capped at 59-60 (every once in a while it would start up at 30 for some reason), and yet it feels smoother than the 85-100 did with hmd vsync turned off. Does anyone have any insight into what’s going on? Ideally I would like to stay above 75 AND have it feel smooth… Can’t figure it out.
Turning VSync off would limit the effectivness of timewarp (if you have it on, you can test it like this), therefore even at 100fps (no/limited timewarp) vs. 60fps (timewarp) you are adding about 6-8ms of rotation latency - the crucial one (translation latency indeed improves a bit, 6.67ms) and some judder. I presume you have your rift in Direct HMD mode? Because in direct mode you get your standard VSync stepping (60fps, 30fps, 20fps etc.), while in extended mode you get adaptive VSync (limit at max, tear at lower fps) so you don’t get those big fps jumps. Also set minimum desired frame rate to 75 (Settings -> General Settings -> Rendering) and I also have smoothed frame rate checked and set to min: 75, max 95.