So I have a bit of a crazy idea...
We all know that interpolation between 30 to 60fps adds lag.
What if a game engine (the logic on the CPU) updates at 60fps, but the GPU only renders every other frame and interpolates the other. That would cut down on lag between action and effect.
Input lag is interesting to me, because even between games with the same frame rate, say 60, it can vary significantly:
Call of Duty: World at War 72.5ms60fps
Call of Duty: Modern Warfare 2 77.5ms60fps
Battlefield 3 157.2ms30fps
Battlefield 4 97.6ms30fps
Call of Duty: Infinite Warfare 39.3ms60fps
Call of Duty: Modern Warfare Remastered 40.3ms60fps
Battlefield 1 56.1ms60fps
Halo 5 63.0ms60fps
Battlefield 4 63.7ms60fps
Titanfall 2 71.8ms60fps
Overwatch 76.8ms60fps
Doom 2016 86.8ms60fps
Killzone Shadowfall Multiplayer 89.8ms60fps
Killzone Shadowfall Single-Player 110.0ms30fps
Now, if you coded a game with an engine that runs at 60fps like COD infinite warfare in this example, with 40ms input lag, but rendered at 30fps and interpolated the image to 60fps your total input lag actually would be better than Doom's true 60fps rendering lag!
You would be one 30fps frame behind, which is 33ms as the interpolation would require a future 30fps frame with which to calculate the intervening 60fps frame it's inserting. Which means if you add the engine latency (40ms - likely less because this actually includes the rendering latency of that game), and the rendering latency being a frame behind to interpolate (33ms), your total latency would be <73ms - so an interpolated 60fps COD would still more responsive than the "true 60fps" Doom.
By not tying your logic update to your graphical update you can reduce the downside of interpolating significantly.
Could this be a technique used by next generation consoles, with fast silicon based interpolation, to reduce the GPU render burden of 60FPS? By decoupling the rendering refresh rate from the logic refresh rate and interolating you get a happy medium between 30fps and 60fps in regards to latency, and indeed can even beat some current gen "60fps" experiences in regards to lag. Who knows, better bluetooth communication between the controllers and the console could also shave some ms off that <73 value.
Not to really anger the "fakery doesn't count" crowd but you could actually use this technique to improve temporal checkerboading too - since the temporal checkerboard would have far more frames to work with (currently only previous frames, but with interpolation it will have future frames too) meaning that temporal checkerboading/injection would be of higher quality and exhibit fewer artefacts. Which would mean you could probably produce a 60fps 4K game by rendering half the frames and half the pixels and it would actually look pretty decent. Not as good as true4K60 but considering it would require about 25-30% of the GPU power (rendering 50% of the frames and 50% of the pixels) of true 4K60 it would actually be a pretty amazingly efficient way of making good looking games. Indeed if there was a silicon based solution to this temporal checkerboarding and interpolation it would cost no more GPU power than making a game at half 4K at 30FPS, and would look far far sharper and smoother and actually have reduced latency compared to a 30fps game if the engine is running at 60fps.
