Station Design Guidelines

[Hoozemans]

So this is not a new question; I've seen many other posts on the same general topic. The previous one with this exact title was a bit outdated, though, so I thought I'd open a new one.

The question is: what can you do to improve performance of your game (outside of bying new computing kit). More specifically: what can you do to improve performance around space stations.

The reason I ask is I've been having inconsistent results with my station designs. I've had massively big stations, 500+ parts, with reasonable (given the total part count of station, docking and approaching vessels) though not stunning performance:

And then I've had this tiny station ... :

(Modlist for above spacestation: https://drive.google.com/file/d/1vajct196DKoGFBZJ_YWFe_QXjAEuXLRe/view?usp=sharing)

... which sports an entirely reasonable 200 parts (including a few docked tugs) but drops my framerate down to single digits per second - and I didn't even try to make the rings rotate (the rings were just a convenient shape for getting stuff to orbit).

So obviously, it's not just the part count, but the type of parts that matter. Some guesses as to what type of parts have the potential to affect framerate:

• Solar panels: they have to keep track of the orientation of the station relative to the Sun and, if they're the tracking type, adjust their angle.
• Docking ports: they may be scanning for nearby targets and adjust their behaviour accordingly. (Though the first pic shows a station with massive numbers of docking ports that nevertheless performed way better than the one in the second pic...)
• The USI Kolonization mod I'm using probably recalculates the current life support status of habitation modules every other.

In the above stations I cheated by using the UbioZur Welding mod to reduce part count, by welding most continuous 'inactive' parts together (like adjacent crew cabins, girders or fuel tanks). Now theoretically this should reduce the load and therefore improve framerate. But I'm not a coder; I have no idea how the code for this mod works or how the code of the game proper has evolved since this mod was first developed. It may be that it's not just about the actual parts, but about the modules inside those parts, which aren't welded - I presume.

So, mods installed, type and number of parts ... what else affects framerate? Can I - can we - come to some kind of consistent set of guidelines for constructing stations big enough to be worth having that don't cause you to grind your teeth at every docking manoeuvre? What parts to avoid, how to avoid them; what mods to install, and which mods not to ...

I'd love to hear your advice and your experiences. Thanks!

EDIT: Another thing, I forgot, that may have impact: settings. Like the max DT per frame spent on physics calculations. The Max DT was lower with the top station than with the one below, but I've been told that bigger is better in this case. Soit, I'll have to experiment with this a little.

SUMMARY TO DATE:

• Limit the number of docking ports. Docking ports, especially unshielded ones, scan the environment for partners to mate with, which puts extra load on the CPU. Also, if you limit the number of docking ports, you'll be limiting the number of craft that are docked at any given time, which limits total part count.
   
• Limit the number of solar panels. All solar panels, not just the ones that actively track the sun, need to be able to calculate their position and attitude relative to the sun, and whether or not any obstacles are present between them and the sun.
   
• Limit the potential for fuel crossfeed. Modularize your station: all fuel (or presumably consumables of any given kind) in one section. See Starman4308's mention of Stratenblitz's video here.
   
• Following AlpacaMall's suggestion: limit the number of lights. I haven't had this problem myself, but I can see how lights might require CPU intensive calculations.
   
• And of course, try to limit the overall number of parts. Mods like UbioZur's Welding mod my help here, or things like the various Station Parts modules I occasionally see mentioned. Sure, you can build grandiose stations just for the kick of it; try and match Stratenblitz's Kerbol 0 if you dare. But if you're looking for something to use as a staging area and (re)fuelling post for forays into the system, then Simpler Is Better (which is what gave me the initial idea for the station in the first pic in this post: basically just a bunch of girders, docking ports and fuel tanks).

Edited May 22, 2021 by Hoozemans

[AlexinTokyo]

Not certain it's your issue, but I've found that lights absolutely murder the frame rate I get.

As in, I can have a 30-odd part rover which putts around fine, but turn on the lights and the physics engine can't keep up and I go into yellow-clock slow down.
I notice you have all the cabin lights on in the second station pic, so I wonder if that has something to do with the problem?

[Hoozemans]

Just now, AlexinTokyo said:

Not certain it's your issue, but I've found that lights absolutely murder the frame rate I get.

The weird thing is that the top station in the initial post was literally teeming with lights - a bunch of projectors at each and every girder intersection you see - and yet its performance was better than that of the station below ...

Quote

I notice you have all the cabin lights on in the second station pic, so I wonder if that has something to do with the problem?

Quick check ... [Turns of lights, attempts docking manoeuvre] I'm not sure. It might have helped a little, but whether it's enough to matter ... ? I should start logging FPS every time I change something. Anyway, thanks for the hint! At the very least, it's worth investigating.

 

[AlpacaMall]

Another tip I've seen is that open docking ports will drop your frame rate significantly. Try only adding the docking ports you're sure you'll need, or using the shielded docking ports.

But then again, if that were the case then I'd have thought the first station would melt your computer...

[Starman4308]

Minimizing the potential for fuel crossfeed may also help significantly, as evidenced by Stratenblitz's recent megaton rocket: https://www.youtube.com/watch?v=iaZ3U6lNvBQ . As a corollary, it may be best to have fewer, large RCS tanks vs. many small ones placed where there's room.

[Hoozemans]

16 hours ago, AlpacaMall said:

Another tip I've seen is that open docking ports will drop your frame rate significantly. Try only adding the docking ports you're sure you'll need, or using the shielded docking ports. But then again, if that were the case then I'd have thought the first station would melt your computer...

I heard the same. That, and solar panels. But yeah, it's exactly that inconsistent behaviour that has me asking questions here.

15 hours ago, Starman4308 said:

Minimizing the potential for fuel crossfeed may also help significantly, as evidenced by Stratenblitz's recent megaton rocket: https://www.youtube.com/watch?v=iaZ3U6lNvBQ . As a corollary, it may be best to have fewer, large RCS tanks vs. many small ones placed where there's room.

Fuel crossfeed is hard to prevent in most cases; especially if your station is a refuelling station (which I'm guessing most are) with a bunch of ships docked. I've seen the video, and I can't fault Stratenblitz's findings - but I'm not sure what to do about it... Well, I suppose I can eliminate a few tanks by consolidating them. It might help. Thanks!

[Mahnarch]

And you definitely don't have other programs running in the background? [Recording/Streaming/YouTube on a second monitor, etc]

 

I looked up DDR4 RAM chip prices and I don't blame you! They know what they want for those, don't they?

Edited May 22, 2021 by Mahnarch

[Hoozemans]

2 hours ago, Mahnarch said:

And you definitely don't have other programs running in the background?

Well, you know, a couple of Windows10 VMs, some docker containers that don't fit in the minikube running in a Linux VM, Firefox (which is a sure performance killer) - the usual.

Nah, the stuff I'm talking about happens whether or not I'm running anything else (although it's worse when I'm running development tools in a Windows10 VM, of course).

2 hours ago, Mahnarch said:

[Recording/Streaming/YouTube on a second monitor, etc]

Actually, display might be a thing under some circumstances. I've hooked up an old monitor to my Mac using a hub ('cause these things only have USB-C ports), and depending on what display mode I'm using, performance of *any* program I'm running, but especially games and VMs, really tanks. But then I've already ascertained that my issues with KSP-performance occur whether or not I'm using external monitors, or doing anything but running KSP, for that matter.

Right now I'm attacking the crossfeed thing. Redesigning my space stations, testing the designs. Should've done that in the first place, since I really hate having to launch all these parts a second time. Although I get to deorbit the old station now, which gives nice fireworks.

I think my next station will be more along the lines of the station in the second pic above: just one massive framework for attaching stuff to. Just wondering what shape to give it...

2 hours ago, Mahnarch said:

I looked up DDR4 RAM chip prices and I don't blame you!

It's not really the price that I'm worried about. I haven't been to the pub for two years, and you cannot *believe* how much money I've been able to save. It's just that it's so much work comparing the specs of candidate memory sticks to candidate mainboards - and it doesn't help that I'm changing the requirements for my new kit every time I sit down to look at them...