This doesn’t surprise me. Raw math, frame gen makes no sense to me unless you’re already hitting 120 FPS natively, and therefore you need at minimum a 240Hz display to make use of it.
Basic math, to generate frames, you must have the next frame ready to generate an in-between. Which means your frame display is delayed by a frame, meaning your input lag is equivalent to natively running at half the rate you’re natively running at. And this is assuming flawless, instant frame generation. For “motion smoothness”, a vague, not all that important element of game feel, IMO.
So, crunch some numbers. Natively running at 60? Neat, you can have the “motion smoothness” of 120 for the input lag of 30. Not worth it IMO, 30 feels pretty rough when you’re used to 60.
Native 120? Alright, the difference in input lag to 60 is way less. 8ms of added lag is tolerable, and with 4x frame gen you can drive a 480Hz monitor. Pretty good, and the time gap is small enough you’ll have minimal visible errors in the generated frames. The question of course being… do you own a 480Hz monitor? Not to mention 120 has solid motion smoothness already, so it’s still kind of a questionable trade. I’d still personally prefer native 120, but it’s at least reasonable.
A debatable sweet spot might be 80-100, 40-50FPS is more than halfway to 60 from 30 (in milliseconds), and you can multiply into more reasonable monitors than 480Hz. 360Hz to fully leverage 4x frame gen is something you’re more likely to actually own.
End of the day though, my core takeaway is that frame gen is incredibly niche. You either need to be obsessive about motion smoothness without caring about input lag, have a hella fast monitor and great performance, or uh… most likely, not understand any of this and want framerate go bigger.
What? Your numbers are right, if you were running the game at 100FPS it would take 10ms to render a frame. Plus your 10ms of additional latency from holding the frame. 10ms + 10ms is 20ms.
If you were running the game natively at 50FPS, it would take 20ms to render a frame. That’s the same number. The total input lag from rendering is identical. Add in the slowdown from your GPU rendering the in-betweens and it’s even a little bit worse.
VSync may complicate this though, depending on the method, since you may already be holding a frame for some amount of time, I hadn’t considered that. I personally use VRR, so it isn’t much on my setup.