VR performance is not really like a monitor performance because it has to provide the frames per second to make the looking around part not slow enough to make you feel ill. A 4k monitor with everything on could be ok to play at 45 fps, but it wouldn’t make you sick. Lag in VR has a threshold where if it goes below the refresh of the screen panels then it’s bad, while normal monitors not so much. Your eyes and balance have to line up, i.e. moving you head and the screen not moving causes motion sickness (one form of it anyway).
I get about 110 fps in DCS 2D 1080p and about 45 fps in 3D with a 2880x1600, more or less. DCS for me is pretty much CPU bound. This optimization if they are only rendering the terrain once, but then copying the scene from left to right view (because you don’t need stereo over a certain distance from the eye) would probably get nearer the magic 90 fps needed for ‘true’ refresh rate of the VR panels.
A lot of people use things like ‘ASW’ and ‘Motion Reprojection’ and that’s the technique where the game only renders 45 fps but the device shows a true 90 fps. It does that by interpolating the scene based on your head movement, i.e. you look a bit left and if a frame isn’t ready to show it ‘shifts’ the last one as if the game did it. Obviously that isn’t perfect but often better than not showing a new frame.These optimizations happen at the VR driver level and DCS doesn’t even know they are happening, just that it needs to provide frames as fast as possible (i.e. at say 50 fps, but not fast enough to draw a new one every 90 fps, so the headset locks it down to 90 / 2 i.e. 45 fps).
This DCS optimization probably won’t get us to 90 fps, but it will provide headroom so that if we’re locked to 45 fps then we can render more detail, more antialiasing (or oversampling, where you provide a resolution higher than the native panel can show, which works like a form of AA) etc, basically make it look better. If it is reaching 60 fps with this optimization, but then locked to 45 fps, then we can add more stuff before it gets close to 45 again.
Hitting 90 every frame in high resolutions is hard, especially in CPU bound things like sims. The HP Reverb which might be our first true ‘clear’ headset other than the Pimax stuff, is a resolution of 4320 x 2160, and that’s without ‘oversampling’ that a lot in VR already use to make things clearer.