Sunsetting the Legacy Computational Solid Geometry (CSG) Engine

Great suggestions, and we agree too! We don’t have anything to share at the moment but stay tuned… :slight_smile:


We are committed to address all community reported issues with solutions or workarounds and appreciate your patience during the transition.

Will the SubtractAsync function receive an update? It breaks the lighting of the resulting union when used within a script. I initially reported the bug to the Bug Support Team back in December 2022, but it still hasn’t been fixed. I also reported it to the post, Studio Beta: CSG Has a New Engine - Vroom, Vroom, Vroom!, and it again still hasn’t been fixed.


@Blast4300 We are currently investigating this matter, and once we have a solution, we will communicate it to you.


@Shirovian Thank you for identifying this bug and for sharing the model with us. We want to inform you that we have successfully reproduced the issue and are currently working on resolving it.


This is incredibly amazing, because now I wouldn’t have to make door frames and windows using parts at an increment and/or have missing or combiner material textures on unioned parts. I am hoping that with the release of this update, we wouldn’t have the problem where unioned parts have an invisible hitbox where you can walk on.


correction on my previous post, sorry for the misconception

Since the last update the align dragged object feature was turned on so alot of builders may end up wondering why their objects will misalign and not slide across the boundary boxes walls which are always straight.

So if anyone is having the issue where the object is misaligned a lil bit its probably because this is turned on.

(Honestly, before it was really noticeable when an object auto aligned to a surface it jittered all over. but im actually surprised that this time it was barely noticeable that i couldn’t see it meaning that the the mesh right now is really good. Really exited to see how they interact with the physics engine )


Well, I wasn’t expecting to be shown just how out of the loop I am today, I never knew it was even possible to make unions in a running game, nevermind that it was multiple entire APIs ago. Yeesh. I don’t see much difference with the results (at least, in the examples given), though, and I haven’t actually made any in about as long either…

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I’m… shocked.

Pleasantly, that is. As a builder, I don’t think I’ve ever been this happy with a Roblox update. I just hopped on to build something after a bit of a hiatus, and I was jumped by the security vulnerability notification, so I got worried not all the issues had been fixed, but when I tried it… Wow.

Everything runs like butter. The separating and reunioning works flawlessly, it’s much faster, and everything is aligned correctly. The only thing I have to do is add smoothingangle.

This is incredible. I literally can’t put into words just how impressed and pleased I am with this update.

I seriously can’t thank everyone responsible for working on this update enough. Every piece of feedback I had was addressed and you all made good on your word to get it into a more than satisfactory state. I can’t imagine how hard the work to get this all working must have been, but it paid off tremendously.

Thank you all. Really. This is a game-changer for me, and I couldn’t be more happy with the results!


Are you guys able to provide any information related to the performance of CSG operations? (For example, what configurations of parts tend to be fast or slow, what combinations of part properties, etc.)

I’ve noticed that there is some variability in how long calls of UnionAsync() take, and haven’t tracked down the cause of that yet.

I am currently doing some work which involves a lot of unioning and would like to see what optimizations I can make (or at least what ways I can prioritise different operations so that I can get the bulk of the work done first and then leave the expensive things last).

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Hello @Shirovian, we’d like to inform you that the issue you reported has been resolved. Please try it again.


The issue is gone, thanks and props on the quick resolution!

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Hey @EmeraldSlash ,
There should be a post coming out soon that goes into detail about both (hopefully exciting) new features for CSG and best practices on how to optimize performance


Will CSG be performant as meshes some day? It’s common knowledge that high use of unions or even moderate use is terrible for your game. I don’t really care to learn blender so I would hope CSG is my fallback.


As of September 18th 2023 (today), CSGv1 and CSGv2 are now sunset. The two Studio setting checkboxes that were available during the grace period are now no longer available.

Thank you to all those that reported issues during the grace period. We have addressed all reported issues in this forum post thread.

Please keep an eye out for a whole slew of new CSGv3 features and performance improvements that will be announced soon!

Happy CSG-ing,
@meshadapt, @syntezoid and @FGmm_r2 (on behalf of the entire Roblox Geometry Team)