[Request/propositon] accessibility: fps lock feature

[TroubledRabbit]

It is NOT about VSync, etc or cry 'I have no TARDIS, I cannot play the game'.

Rationale:

(personal) it had really hurt my eyes namely: sudden jumps in fps from high to low and vice-versa, sadly it makes me dizzy.

(general) I know that having a hardware which is able to deal 10E5 fps during the necessary, virtuos and godly smashing Vigor Cartel in ugly faces of theirs is something desireable and a source of pride if someone has the metal for it.
However, there are benefits in setting the effective fps lower (basically locking it at the certain rate) than the machine is able to give directly at the application level:
- it is more effective and not prone to producing problems and artifacts (like using Vulcan fps lock command sometimes),
- creates less stress on the machines reducing heat and noise if one so desire,
- gives (relatively) stable visual performance at the desired comfortable level* reducing (or completely removing) not fun effects for the old grumpy turds like me, or someone with particular eyes problems; jumping from 60 to 28 and in a moment from 28 back to ~50 really can give a literal headache.

Complexity:

in theory almost none but I obviously have no idea how the game engine works so: 'undefined'.

/*
*I am playing with fps locked at 30 at the Vulcan level (basicaly in the 'PS3 mode'), which is working fine but suboptimal, the game itself would manage this probably better than external layer I suppose.
I completely understand if it may seems ridiculous for someone but, gimme a break, I am old, I have actually played the original Elite on 8-bit machine, my expectations are therefore at quite different level
*/

[Blitz4]

This is important. More than most would believe. The framerates below aren't the same for all, I chose the most common. I also mention framerate when that is not at all how you measure these things, you use frametime, but did so for simplicity.

1. If your framerate goes from 200 to 20 you won't have an enjoyable experience.
2. If your framerate goes from 200 to 20 you will waste electricity and unnecessarily heat up your room.
3. Games over 120 fps don't feel or look better, there's a tapering effect of framerate.
4. Games under 50 fps noticeably have stutter and make the experience poor.
5. If your framerate goes from 200 to 60 during a point when you are precisely using your mouse/joystick, you will notice a difference. If you're aiming, you'll be less accurate.
6. If your framerate goes from 200 to 60 during a point when you are precisely using your controller, you will not notice a difference as much as #5 above but it's still present.
7. Commonly to solve these types of issues it is suggested to cap your framerate. Not everyone knows the best way.
8. If you cap it using your GPU driver or RTSS or SpecialK, you will most likely introduce more input latency into your game than if it was done properly by the game.
9. Capping framerate per mentioned in #8 above and experiencing a sub 50fps framerate will make the effect feel worse than it is due to the unnecessary input latency added.

There's many tests done and it seems the 3rd party options mentioned in #8 will introduce more than 1 frame of input latency on average . On average mind you. I like this test comparing the 3 methods. https://www.reddit.com/r/allbenchmarks/ ... x11_based/

It shows going from 80 to 60 fps adds over 25ms of input latency no matter what they choose. The average should be less than 1 frame. But 3rd party options are limited, not reliable, not consistent. One rule I heard John Carmack mention was 1/50fps = 20ms that's the minimum amount of time that the average eye can notice a difference of movement, this is why 50fps was mentioned in #4. Another rule that's farily common, is 90fps minimum is required for a VR game. Now if #9 happened in a VR game, you'd be more likely to vomit due to the input lag.
a funny demo of that: https://www.youtube.com/watch?v=_fNp37zFn9Q