[V7.18.2 - ground combat] - minor / performance / not a new issue - sometimes after starting a ground combat mission, FPS is 1/2 to 1/3 of normal

[fusion-waffle]

Description

minor / performance / not a new issue - sometimes after starting a ground combat mission, FPS is 1/2 to 1/3 of normal

 

This behaviour IS NOT NEW to 7.18.2 or any recent build, I've seen something like it every now and again over the last month or two, but don't think I've reported it before. It could be something to investigate if there's capacity to revisit performance issue in the future.

 

What Happened

Mid-late game, base defence mission.

In the base defence deployment phase, I noticed my machine was running at unusually low 22 FPS, vs 45 - 60 FPS I normally see in combat (outside of AI turns where sometimes it drops to 2 FPS).

The low FPS of 22 persisted into player turn 1. 

Saving the game, exiting to desktop, restarting the game and loading back into the mission worked around the issue -- the FPS was restored to 60.

Further Info

• I suspect this issue is more common with missions that begin with full map vision - I'm pretty sure it also happened during cleaner convoy ambush (earlier in this v7.17 campaign)
• If other players do not experience this issue,  perhaps it could be linux-specific (I play via steam proton from ubuntu) or something hardware specific
• please see attached f11 bug report -- this was captured AFTER the workaround of saving, exiting game, loading game again:  bug_report_2026-04-02-17h14_gc_7.18.2_user_f11_0.zip

[Kouki]

2 hours ago, fusion-waffle said:

Description

minor / performance / not a new issue - sometimes after starting a ground combat mission, FPS is 1/2 to 1/3 of normal

 

This behaviour IS NOT NEW to 7.18.2 or any recent build, I've seen something like it every now and again over the last month or two, but don't think I've reported it before. It could be something to investigate if there's capacity to revisit performance issue in the future.

 

What Happened

Mid-late game, base defence mission.

In the base defence deployment phase, I noticed my machine was running at unusually low 22 FPS, vs 45 - 60 FPS I normally see in combat (outside of AI turns where sometimes it drops to 2 FPS).

The low FPS of 22 persisted into player turn 1. 

Saving the game, exiting to desktop, restarting the game and loading back into the mission worked around the issue -- the FPS was restored to 60.

Further Info

• I suspect this issue is more common with missions that begin with full map vision - I'm pretty sure it also happened during cleaner convoy ambush (earlier in this v7.17 campaign)
• If other players do not experience this issue,  perhaps it could be linux-specific (I play via steam proton from ubuntu) or something hardware specific
• please see attached f11 bug report -- this was captured AFTER the workaround of saving, exiting game, loading game again:  bug_report_2026-04-02-17h14_gc_7.18.2_user_f11_0.zip

Thanks for the report, does the performance drop happen when the game has been running for awhile? I've tested this on my end but did not really get much of a fps drop except in the first enemy turn.

[Skitso]

I've experienced bad performace in deployment phases since forever.

[fusion-waffle]

45 minutes ago, Kouki said:

Thanks for the report, does the performance drop happen when the game has been running for awhile? I've tested this on my end but did not really get much of a fps drop except in the first enemy turn.

Perhaps -- but "awhile" might be closer to 30-60 minutes, rather than 8 hours.  E.g. play a ground mission, go back to the geoscape, play a second ground mission.  It might be more likely to happen in the second ground mission (I'm just guessing, no data!)

 

The poor framerate isn't exclusive to the maps with deployment phases -- it happens sometimes in other maps as well.  but the issue does seem to manifest often on maps with deployment phases.

 

If no one in the dev team has investigated this before & has a machine that can reproduce bad framerates in deployment phase with a profiler attached, it may reveal some low hanging fruit.

Edited April 2 by fusion-waffle

[TuTurambar]

I have the same issue. Yesterday I started a game, played 3 missions, ni issue at all. Today I start the game, play 5 minutes, then start a nighttime ambush mission, and my FPS drop to around 15.

 

I am playing on Linux too, and tried using gamemoderun and mangohud, it did not improve significantly (around 20FPS). Reloading the save does not fix it either.

[TuTurambar]

It seems to be fixed when using proton-experimental. I tried a bunch of other Proton versions, including GE, this was the only one doing it.

[TuTurambar]

I got the issue back. I was playing for some hours, everything was running smoothly, and then around the third/fourth turn of a night crashed UFO mission, I'm back at 20 FPS. Reloading the game does not fix it, so it's not a memory leak.

Also I'm surprised by the "minor" tag of this topic, playing the tactical game in these conditions is very bad.

[fusion-waffle]

4 hours ago, TuTurambar said:

I got the issue back. I was playing for some hours, everything was running smoothly, and then around the third/fourth turn of a night crashed UFO mission, I'm back at 20 FPS. Reloading the game does not fix it, so it's not a memory leak.

Thank you for sharing what you've tried so far & that it didn't help.

 

When you say "reloading the game does not fix it", do you mean that you fully exited the game process before restarting the game & reloading?   I found I could generally work around this issue by doing that.

[TuTurambar]

Yes, I closed the game, returned to desktop, started the game again, loaded the save, and it was still lagging.

Since then, every battle has been capped at 20 FPS.

[Chris]

On 4/9/2026 at 9:31 PM, TuTurambar said:

Yes, I closed the game, returned to desktop, started the game again, loaded the save, and it was still lagging.

Since then, every battle has been capped at 20 FPS.

Can you provide a save? Or ideally saves from a couple of tactical missions that were affected?

If this is reproducible after a clean restart of Xenonauts 2 then it'd be interesting to see them. Maybe we can get a user with a dual boot machine to test the saves in Windows and in Linux to see if this is actually a Linux-only issue or not.