Honestly, you're not making any sense.
Reason is because difference between 1 and 5 secs is actually pretty significant (more so on higher increments), both functionally and visually, when implemented as in TFTDextender. In favor of 1 sec of course. Don't think it would break compatibility or anything, unless OXC does not support clock precision bellow 5 sec in its savegames. Guess #1 is off the table in that case.
Have you seen the 1sec implementation anywhere?
Do you know how the TFTDextender works?
How can you say it will have any significant impact?
Don't post random guesses please... you are confusing yourself and all who will read it in the future.
Also "1sec" and "5sec" ARE the increments... saying "1sec" increment will work better on higher increments just makes no sense at all man.
It's the same as saying "Going at speed 10 km/h works best if you go at 300 km/h".
Either we have a language barrier here, or you're not paying attention to what you're saying.
In short: terminator moves smoothly in all cases, even when for example increment is set to 1h while Clock Speed it set all the way left (250ms).
That is absolutely NOT true! Dude you make my blood boil.
With clock speed all the way left (250ms), the game refreshes the state only 4 times a second and it is visibly stuttering like crazy, on all increments (5sec, 1min, 5min, 30min, 1hr, 1day)
DO NOT USE THIS SETTING.... that is what makes your game not smooth.
Not sure how it's implemented in extender, I reckon calculating and updating every second of that 1h in OXC would be a computational overkill. If I understood correctly this method wouldn't be older hardware friendly so making it optional, like other extender features, would be required.
All games use exactly the same calculation in the background, xcom, xcom+extender and also openxcom.
The game internally ALWAYS calculates in 5 second intervals... it is NOT a computational overkill, it is always done, on each increment setting.
Here's the proof and explanation:
https://github.com/OpenXcom/OpenXcom/blob/master/src/Geoscape/GeoscapeState.cpp#L622Globe (picture) update on the other hand is done based on selected increment and configured clock speed.
Your hardware is also NOT a problem... even on very old PCs, this is no issue (assuming reasonable video settings).
When I said "extra slow devices", I meant things like super old phones, consoles or any other exotic hardware... your 15-year old PC is just fine.
Bottomline:- if you want to increase "smoothness", increase the clock speed (move slider more to the right).... again DO NOT MOVE SLIDER TO THE LEFT, EVER... that is a sure way to decrease "smoothness" rapidly (regardless of chosen increment)
- if you want to decrease the "speed", use the increments (5min, 1min, 5sec, etc.)... "30min" is faster, "5sec" is slower