Humanoid Controller Weird Idle Movement on CFrame w/ floating point errors

I was hanging out with @Onett and he showed me a game breaking bug in Bee Swarm Simulator that started happening today. He has boss’ with Humanoids. After a lot of debugging, we narrowed it down to be that he must have some parts in the game which have malformed CFrame, perhaps due to an old dragger or something.

In the game, the CFrame is CFrame.new(-178.677597, 65.7050323, 486.565765, -1, 2.30948807e-21, -3.86501782e-08, 1.3433506e-21, 1, 2.48687975e-14, 3.87503114e-08, 2.48687959e-14, -1)

And when a Humanoid is placed on this part, the following occurs:

And when the CFrame is CFrame.new(-178.677597, 65.7050323, 486.565765, -1, 0, 0, 0, 1, 0, 0, 0, -1), nothing abnormal occurs.

Of course, he could run a script to fix all of the parts in the game … but all of the components that need to be zero already seem to be relatively close to zero, and this was working fine for years, so we wonder if something weird happened in past ~24 hours that might have caused this?

Repro:
coconut_crab_bug_repro.rbxl (79.6 KB)

4 Likes

As I was writing this up, the repro suddenly stopped working … and I just checked FFlag tracker and now am thinking it might be related to SimdBvhRayCast which was just disabled… so hopefully an engineer knows has already encountered this bug and rolled back for that reason.

3 Likes

I believe the flag was reverted here: Raycasting suddenly stops working, won't detect any new parts

3 Likes

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.