When i'm using Rubidium i get 147-114 or less when there's fire? Vanilla Minecraft (no mods) /Magnesium/Optifine fluctuates from 200 (Max fps) to 197-179-186 is there an specific reason why this is ? Since Rubidium is supposed to be the updated version of Magnesium i expected them to have an equal impact on performance. (Rubidium is using a freshly generated config with 200 fps/61 of brightness and 12 of render distance) (Example : when a generated lava pit on a forest burn it's surroundings let's say 4 to 5 trees the performance just completely drops.)

Are you using Oculus, and if so, which shader do you have running?

Not using shaders.

Yes any kind of fire.

Hmmm... I am unable to reproduce this issue when using Oculus with any shader. I will see if I can reproduce this without Oculus.

Are we talking any kind of fire here? Such as one I would create just be using a flint and steel on the ground in front of me.

All right, I just tried this out on a default 1.16.5 instance with only Rubidium, and I don't even get a blip of framerate change. The range at 115-118 FPS before fire, and have 115-118 FPS after fire. No change at all.

I don't know what is going on here. You only get this with fire and not any other shader effects? I would really expect any kind of particle and shader effects to have problems and not just fire.