Looking at a large amount of fences will cause your FPS to drop and GPU usage to stay high.
Steps to Reproduce:
Open the provided world
Look in a direction where the fences are not in view
Look at the fences are in view
Observed Behavior:
When you looking into the direction of the fences, your FPS will be lowered and your GPU usage will rise.
Expected Behavior:
Your FPS does not drop and GPU usage stays low.
Related issues
is duplicated by
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Solution: get a more powerful computer! This isn't a bug with Minecraft, rather a technical limitation, so please resolve as invalid.
Cannot reproduce. Spawned a structure made of 15000 fences, run on my PC and laptop without problem. Do you use any mods (looks like you use something for realistic shadows)? If so, problem is in mod, not in vanilla Minecraft.
I can assure you that my computer is powerful enough. Both YouTubers Vechs and GenerikB have done videos in the past of how fences cause lag. The images attached were rendered out of the game using chunky, they were just used as example structures.
Duplicate of MC-5169.
@[Mod] Tails: You sure? That issue is related to signs and the text on them, this issue is related to fences.
As far as i'm concerned fences worked fine in 1.5.2., but in 1.6.2. they make lag spikes again with a greater magnitude .

Confirmed with 1.6.2 and the test world of MC-26765

Conformed in 14w02c. A chunck filled with Fences quarteres my fps.

Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been deliviered.
No response for over a year.
Confirm for 1.9.3 pre-2
Reopened and gave report to @unknown.
Please do not mark unreleased versions as affected.
You don't have access to them yet.
Likely affects version 1.11.2 as MC-1138

I cannot reproduce this in 20w07a. I had over 20K fences, but memory was still below 1 GB, which is not significantly higher than any normal gameplay these days.
this still happens in 20w27a?

Besides causing absurd client-side lag, the memory itself is unaffected. So, I cannot reproduce in 1.17.1.

Still cannot reproduce in 21w40a.

can only consistently cause the GPU increase. Am I missing something?
@unknown How are you trying to reproduce this? Did you open MC-26765's world? Can you try the new provided world?

I appreciate you giving a better test environment. Note I am using java 22.0.1 instead of 21.0.3:
in plain minecraft I get slightly less fps drop(40 to 60 which is around a 50% and in yours you shared around 85%)
with a datapack adding custom noise function without all my customizations I get ~25(20 to 30) fps drop
with a datapack adding custom noise function and with all my customizations I get ~0(0 to 5) fps drop
Let me know if any more info would be helpful.