Switching all games to the PGS Physics Solver next week (March 4th, 2019)

Hi All!

We are switching all Roblox games, regardless of current solver setting, to the PGS physics solver on Monday, March 4th, 2019.

Please see this previous post for more information:



Can’t wait to see the future to this PGS Solver, it’s sad to see the TemporaryLegacyPhysicsSolverOverride button leave but eh, as long as we get best out of PGS.


Great change, really excited to see what the future holds.


Can’t wait. Always exciting.


It had to come, but in contrast, many old places will be broken by this. I understand Roblox need to move forward with their physics

Roblox have done some fixing on their side, mainly, the hinges FINALLY being locked to one axis, which is enough for me.

BodyMovers seem to be more stable as well


It’s a good thing it finally got removed but I did find the old solver better in some very few ways. One of them was not instantly over-straining the dam thing when you tried to deal with a few physics items - and I hope in the future the new system can be made to be as robust as the old one was. It’s still an easy fix going forward to avoid over-straining with small gaps but that can be limiting in some circumstances.

Other than that the improvements and weird bugs fixed made to the new PGS Solver make it more attractive than it previously was. I’m going to continue to experiment to see if I can make a compromise on not over-straining the new system - as I already know how much smoother it is in general compared to the spring physics touch something and the door spazzes out anyone?


I feel as though constraint physics are far superior to spring physics in every sense of the word. But, let us not forget that along with the constraints feature to physics updates that we have also been brought other goodies - including attachments, which we can put items like sounds and lights in.

Not just physics have been updated with the advent of constraint physics, but functional updates have also been added in which have helped much in the development process.

A welcome change. Thank you for your years of service, spring physics. It’s time we part ways now.


It would be nice if we had a few more than 6 days notice. I’m working with @Synchorus and @dr01d3k4 on the game Steam Age, and this has caught us completely flat-footed. We may even have to close the game because of such short notice.


You have had over 3 months to prepare. In addition to this, I’m pretty sure a banner appeared in Studio warning you to use the new solver if you weren’t already.


The banner would only appear until you clicked the X, then in all future Studio instances it would only appear when Studio is loading a game and the viewport wasn’t rendering correctly. (i.e: only for a frame or two).

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Is there still going to be an option where we can still use the old physics solver with approval? Conveyors don’t work with the new PGS solver and the movable parts phase through anchored parts often on map locations very far from (0,0,0). Those bugs were there 1-2 years ago when I first tried to convert. A year later it is still not solved. Roblox should at least fix the pgs physics solver before forcing everyone to switch. This is literally going to kill the aviation and transportation industry.

My game is literally broke now… https://www.roblox.com/games/172205561/Hyperloop-Simulator-Lasagna-Pod


This does not sound like a valid reason to me. If you dismissed the banner, you already saw it and were aware that this change was about to happen. If you didn’t pay attention to what the banner said, that would be on you and not on Roblox.


Yeah, there should be no reason to delay this just because some people weren’t paying attention. Roblox gave a pretty fair amount of warnings prior.


Hi NWSpacek - I’m sorry you might have to close your game for this reason. Please let us know if you are having problems with the migration.

Regarding the prior notice: We announced this numerous times over the last year or so, including these posts from last August and November. I strongly recommend reviewing them for important information you may have missed.


Are you guys aware of the fact that conveyors don’t properly work on PGS and moving bodies often phase through anchored parts in locations far from the (0,0,0) origin? I have a train game that has a 50000 stud long map. Toward the end of the map some parts sometimes start phasing through each other. This is a PGS issue, because the problem no longer persists once I turn it off.

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Can you please post a simple repro so we can investigate and fix this?


The first clip is how it is supposed to work without PGS

The second clip is what happens with PGS physics solver

In this clip, the vehicle doesn’t move when the conveyor is fired. Instead the character is launched if it leaves the vehicle

The collision of PGS physics solver is way too stiff, which often causes the vehicle to violently bounce around track and derail at high speeds. The success rate for a complete run without PGS is 90% and still 0% with PGS on even after 15-20 attempts.

The instability and bugs of PGS physics solver is game breaking and should not be forced on games until the system is improved. I’ll have to close down my game for the same reason as Steam Age; the conversion will likely require rebuilding the whole game. Even if I do rebuild the whole game, it is unlikely it will ever be as stable with the current PGS. I tried converting about 1-2 years ago, it has improved since then, but still needs a lot of work.


I’m afraid I will have to also permanently put on hold the revival of one of my old games (which relied heavily on the SpringSolver), as PGS handles BodyMovers differently, I would’ve liked to attach a repro file so you could see for yourself the issue here but I’m currently on mobile…
(I’ll edit the post once I get the repro file)

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Could you provide a simple repro level so we can investigate the sources of the problem.


This is about 2/10 of the game with the basic systems in place. This was built in 2014, so the workspace is pretty messy
Hyperloop.rbxl (2.5 MB)

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