PGS Disabled breaks Swimming and Speed

You can’t jump while underwater with Roblox Smooth Terrain water with PGS disabled.

Whereas with PGS enabled, you swim up faster if you hold space bar/spam tap it.

Using Windows 10.

Water_Repro.rbxl (16.0 KB)


Is there any reason you’re disabling PGS?

It is recommended that you use PGS within your game.

cc @Joshua_Falken

Ships I use behave better with PGS disabled.

Hmm, my honest solution to your issue would be to re-build your ships to work with PGS.

I don’t think Roblox will make updates to the legacy physics solver as PGS is the new system.

I could be wrong but, I’d recommend doing the above and see how it goes. Sorry I couldn’t be of much help.

They work the same as they do with PGS enabled. Just with it disabled, body gyro and position are way more stable. So I prefer that.

Could you try AlignPosition/AlignOrientation instead of BodyPosition/BodyGyro? They’re newer PGS constraint-based objects with similar functionality and should be more stable. They’ll only work with PGS enabled.

They’re constraints and use attachments. You’d put Attachment0 inside your boat and put Attachment1 in some baseplate part. Set the CFrame on Attachment1 to set the target position/orientation. Enable AlignPosition.ApplyAtCenterOfMass for more BodyPosition like behavior, otherwise the forces will be applied at the attachment point, which can cause rotation.

If this is the new way for simulating physics on Roblox, that’s awful. Creating a dummy part and asking Roblox to please align Part0 with Part1’s attachment instead of just adjusting Part0 outright is a hack.

This isn’t for simulating, this is for the use case of legacy BodyMovers.

It might be more convenient if you didn’t need an attachment or an intermediate part for aligning with world space, but this is where we’re at now. We’re discussing possible improvements among the physics team. For now I usually put my “world space” attachments in baseplate or some other anchored part at 0,0,0. Same effect.

If you have any other suggestions feel free to message me, don’t want to veer too far from the OP’s issue.

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So problems with PGS disabled will no longer be fixed?

If it’s any consolation, you can stick the attachment in Terrain, so that no intermediate part is needed.

almost no development time will be allocated to bug fixes or improvements with the legacy solver.

Do you know if this is a regression at all? We do plan to remove the legacy (non-PGS) physics engine entirely at some point in the future (TBD), so we’re reluctant to mess with it at all. If it’s a regression we’d still want to investigate.

If you do have any issues with the newer PGS-based physics engine that make you not want to use it we’re really eager to hear that and make it better.

My only issue is that the behaviour to the ships changes dramatically when switching to the new PGS solver.

Another bug with it turned off:

100+ speed walking on water.

Reproduceable steps:

Switch to pirate team, select the musket. Press F, so you present the musket and now walk into the water.

Hello, I think I have some kind of issue with PGS which stops me from using it completely. I can provide a repro file with the ship which has this problem if it’s needed. My ships become very unstable with the PGS physics solver

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