Could someone explain the "Max physics delta-time per frame"

[Gotmachine]

2 hours ago, flart said:

Max physics delta-time per frame slider to the right (0.12):
game_time is closer to real_time (less slowdown aka the clock is "more green"), but in the cost of visual FPS and stability (less FPS, more change for kraken), 

Max physics delta-time per frame slider to the left (0.03):
max out stability and visual FPS (more FPS, less change for kraken), but in the cost of game_time/real_time ratio 
(more slowdown aka the clock is "more red" aka 1 game second will last more (2,3,4...etc) real seconds)

Yep, that's a good summary.
Although it should be noted that the "less/more stability/kraken" bit only apply to a few corner cases.
Specifically, it only apply when a part is "instantiated" : flight scene loads, previously unloaded vessel entering physics range, EVA/Boarding, and possibly EVA construction.

The current KSPCommunityFix patch only apply to the first case (flight scene load).
I have a more "technically sound" fix, but I'm reluctant to release it as it alter the default KSP initialization sequence, and there is a small chance that this have unintended side effects on other KSP stuff/mods.

[damerell]

On 2/5/2016 at 10:29 PM, NathanKell said:

With the slider all the way on the right, that's saying you can have a maximum of 1.5 (0.03s = 20ms x1.5) physics frames per visual frame

On 11/14/2021 at 4:24 PM, flart said:

Max physics delta-time per frame slider to the left (0.03):

I'm necroing this thread because I've pointed more than a few people to it over the years, because it's still the thread you hit if you try and search this forum to understand this option, and because reading this thread is very confusing until you realise that the left and right ends of the slider _changed ends_ between 2016 and now. What NathanKell wrote is entirely right - but if you just skim it, you'll move the slider the wrong way. What flart wrote is just quoted here to make it clear the slider has flipped ends; they make the common mistake about one setting or the other making the Kraken more likely.

Here's how I understand it (and AFAICT this matches up with NathanKell):

• No matter what this setting is, every physics tick represents 20ms of in-game time. No change to this setting alters physics behaviour. (Physical time warp makes physics ticks represent more in-game time, and that can result in different physics behaviour).
• If the setting is low (in _recent_ KSP versions, the slider is to the left) and your computer is too slow, game time will slow down relative to real time (yellow clock) rather than the frame rate being reduced.
• If the setting is high (in recent KSP versions, the slider is to the right) and your computer is too slow, game time will stay the same as real time but the frame rate will reduce.

Of course, there's limits to this: if the physics tick alone takes more than 20ms to simulate, the game time will slow down no matter how low the setting is and how fast your GPU is; if it takes 40ms to draw each graphics frame, you'll never get more than 25fps even if you have a one-part ship sitting still.

[NathanKell]

Huh. I had no idea the slider flipped, I'll edit my post. Although that will obsolete your excellent reply?

EDIT: Linked to your reply along with the edit, so all should be well.

Edited June 12, 2022 by NathanKell