New Studio Feature - CollisionFidelity.PreciseConvexDecomposition (Enabled Globally)

I have been waiting for this feature for a long time! Thank you, you are appraised!!


Great feature I’ve been wanting for a long time.

For example:

The original mesh of a curved tube

Collision before

Collision after

There are still some slight imperfections where it isn’t perfectly smooth but it’s not even comparable to before.



Yeah slight imperfections that extrude 1/100th of the boundingbox length from the surface is something that can happen with the algorithm. (See my previous reply to Hobbyist_Games above).

My hope is that in the future I can expose the “tuning” of the algorithm so that users can define the “distance” of acceptable imperfections.


Yea, this would be great!
Otherwise, this really is one of my favorite feature of 2020 and it’s personally going to be quite useful for my project. I already feel like I’m going to have quite some fun playing around with that!


This is soo cool! I can imagine alot of things possible with this now. Yesterday I was making a test of a earthquake where the ground “breaks” in half using SubtractAsync. But you couldent fall into the hole that it was making because of the collision. I think this will make it possible thanks alot!


Here’s a plugin by @CloneTrooper1019 that allows you to toggle the ShowDecompositionGeometry setting, it is very handy for trying to limit your “PhysicsPart” memory by sacrificing some collision accuracy


THIS IS INCREDIBLE! Smooth slide time!

EDIT: This slide mesh is still broken up into sixteen pieces.


This is great! The physics generator is impressive, but there are still so many cases where I know exactly what I need but the results are far too complex (or don’t match the geometry.)

The worst experience I’ve had is with this cherry tree trunk. I spent hours trying fit a small burrow into the tree for tiny pets to use, but everything I tried was unusable.

I tried using PreciseConvexDecomposition on it and it resulted in a crash. I’m not sure what I expected considering how complex the small roots are. I know exactly how I want to approximate the roots, there’s just no way to do it.

I could try approximating it with invisible parts, but what I need is already in the engine, I just need the tools! I’ve started seriously considering reverse-engineering the physics format so I can make my own physics editing tools, or at the very least copy/pasting mesh data manually from .rbxlx files for similar meshes that could reuse the same physics data.

There are also common cases that could be approximated with a sphere or non-axis-aligned cylinder/box.


I can’t seem to enable this; the option is not selectable in the dropdown menu for me

Whenever I try selecting “Hull” (The second-to-last option) and then pressing the down arrow, studio crashes.


I was able to select this as an option weeks before this feature was released as well (only by pressing the down arrow on the dropdown; I couldn’t mouse over it. See the video above.), but it was crashing studio

Now I’m still getting the same thing, where I can’t select it with my mouse, can select it with the arrow keys, but studio crashes whenever trying to enable it. Re-installing Roblox Studio doesn’t seem to work.

edit: Oh, I didn’t realize from this post it wasn’t live live. :frowning: I forgot to enable the beta feature

However, it seems that when I disable the beta feature, meshes that I set to PreciseConvexDecomposition still retain their hitboxes


Can you please PM me the tree trunk? I want to see whats up with that.

Updated the original post to mention the Beta Feature more directly.



I didn’t realize it was a Beta Feature but still managed to select it using the arrow keys.

Edit: Selecting using arrow keys was my problem. The collision mesh looks amazing with only 30% more data added to my save relative to CollisionFidelity.Default:


I cannot express how much I love this update! It’s incredible!! Thank you so much, you are a hero!


interesting. This could possibly lead to liquid simulation, but right now I have no use for this.


Awwww bummer, I was hoping for better composition in crevices/bowl shapes so that when I paint debris on rocks, it can bunch up like it would in nature! However it is better than before for the more open, smooth surfaces of rock


This is amazing. I can finally avoid having to decompose some of my meshes into 20 convex surfaces, although an Exact option is still required in some cases.


Can’t wait to make some roads in Blender since it’s so much more convenient and efficient, and have them actually collide properly in studio!



Since fast flags are engine-level, why couldn’t you just not make PreciseConvexDecomposition exist if it’s not enabled?

(Assuming this was a fast flag, I never got an answer on that)


This has been enabled in studio for a while but just crashed it until now- I’m glad it’s not teasing me anymore lol
However, a little disappointed it didn’t fix my primary use case- shadows.

The shadows on this more accurate geometry is somehow even worse than Hull?? I just want to be able to make unions with good collisions and shadows without it looking like crap. :confused:


I Just spot on been wanting that for a long time thanks!!

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