For some reason, if I equip the jetpack with or without shadders it drops my GPU usage and thus the FPS
This is happening in a modpack I created and I don´t know the reason
I suppose it could be related to flywheel or Iris or Geko3D stuff but yeah
If you need more info plz contact me on discord Garueri#2187
Currently, the issue is 100% times repeatable

Could you please specify which version of MC and SimplyJetpacks you use? Also if you already open an issue here, I would suggest, you also post the info here, I do not have the time nor will to personally contact a person everytime there is a new issue. Besides if you cannot pinpoint the cross mode compatibility problem or rule it out, I would like it, that you first test this further so we have a specific problem. I understand it is frustrating, but I do not have the time to test every mods compatabilty, and shaders almost always break stuff in some kind of way (at least back in optifine days not that familiar with Iris)

wassup bro
Ok imma do some testing and i’ll be back with more precise info, thxs for replying, sorry for being extremely info lacking

Closed by accident, will be back

Could you please specify which version of MC and SimplyJetpacks you use? Also if you already open an issue here, I would suggest, you also post the info here, I do not have the time nor will to personally contact a person everytime there is a new issue.
Besides if you cannot pinpoint the cross mode compatibility problem or rule it out, I would like it, that you first test this further so we have a specific problem. I understand it is frustrating, but I do not have the time to test every mods compatabilty, and shaders almost always break stuff in some kind of way (at least back in optifine days not that familiar with Iris)

I've noticed the issue myself and did some more testing.

I'm working on 1.20.1 and noticed that equipping any jetpack, whether its in the Chestplate or Curios slot, reduce my fps by a lot, from 240 to 80 in fact.

I first thought of a mod incompability since my modpack currently has 270 so I tried launching an instance with only SimplyJetpacks2 installed, no lag were noticeable.

I then slowly readded mods that in my opinion were likely to cause the issue, mostly optimisations mods, things like Immediately Fast, etc... but once again I couldn't notice a difference when equipping a jetpack.

I then decided to start slowly readding random content mods and that's when I started noticing lags coming from the jetpack.
The problem is that the issue doesn't seem to happen from a mod uncompability as in fact adding any content mod seem to make the jetpack lag just a little bit more no matter which one I choose. While in my modpack with 270 mods the fps goes down from 240 to 80, in my test instance with 120 mods fps goes down from 240 to 160 and adding any more mods seems to reduce fps further more while once again removing any seems to increase them.

I am unfortunately quite unsure of my results as I couldn't get anything significative from it (as a clear culprit) :/ but could somehow the issue be caused and exagerrated the more assets Minecraft has to load? That would explain why adding any content mod would seem to slowly feed the issue while optimisation / qol mods didn't look to do so.

Hope I could help! Because currently I can't quite keep SJ2 as it is and it sucks really, as I really love the mod. :)
If any more info is needed, please ask me! I'll try my best to answer.