Parts moving causes lighting to recalculate resulting in significant performance impact

Reproduction Steps

I’ve attached a simple reproduction file privately. The bug does not happen in studio only the client. So opening this up in vanilla studio and looking at the microprofiler will not display the bug.

It’s important to note that humanoid related parts do not seem to cause this issue (for example, other player characters)

Expected Behavior

When parts move the lighting should not recalculate as it does currently thereby causing such a significant performance impact.

Actual Behavior

When parts move this causes the lighting to recalculate constantly which causes a significant performance impact.

In the following video the propeller is spinning via a hinge constraint and the gui button anchors/unanchors it. When unanchored and spinning the performance drops significantly because the lighting is constantly recalculating.

Issue Area: Engine
Issue Type: Performance
Impact: High
Frequency: Constantly
Date First Experienced: 2022-07-14 00:07:00 (-04:00)
A private message is associated with this bug report


Same issue! I had to cut out a big part of my game’s lore (has to do with a spinning thing) because of this.


Just wanted to follow up on this bug, since this is causing significant performance issues in our game Adopt Me. Thanks!


Hi. Thanks for the reports @EgoMoose @NewFissy. I wonder is this a new behavior for you or was this happening for quite some time?

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I have seen this issue.

I did recently see that the “future is bright” lighting engine has been getting very slow and very performance-heavy, and this impacts multiple devices. The Future technology is additionally very slow, and it starts to become faster at graphics level 2 (this is a different issue, I believe it’s PBR working normally).

Now, I don’t recall when this started but it has been going on for at least a month (and clearly started sometime this year). While in “Run” mode or playtesting, I had to switch over the lighting technology to “Compatibility” and turn off shadows to see what was happening without it taking forever.

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Ever since the new PBR materials, ive noticed performance gets worse, 2022 textures off, game runs fine, as soon as you turn them on, FPS vanishes -
Specs are as follows –
Ryzen 5 5600x
Radeon RX 6600 XFX 8GB
8GB Ram

running at 1080p
While I know PBR does change how lighting works, shouldnt kill my FPS this bad

Without the PBR textures I get around 500~ FPS unlocked
With the PBR textures I get around 100-200 FPS locked


Hi @ConvexRumbler, thanks for your patience! We’ve tested through all our test devices again that were previously experiencing the lighting recalculation issue, and it appears the issue has been resolved. We haven’t changed anything on our end, so it appears it was either intentionally or unintentionally resolved on the Roblox client.

To answer your original question, we only became aware of the issue as of the date of this bug report. It was likely happening before, but we weren’t sure how long.

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