Auto convex collision doesnt do anything

I click auto convex collision on my mesh settings… and it does nothing. Takes a split second and no outcome… just does nothing. Box simplified works… remove collision works… all that works… but auto convex does nothing at all…

I imported the model regularly with autogenerate collision set on. I remove collision then try to do auto convex and theres just nothing there… Any ideas?

Hi kurlyo3d,

The Auto Convex Collision in the Collision dropdown only opens the Convex Decomposition window (bottom-right by default). You then have to adjust those setting and hit apply.



If I misunderstood what you are see, please let me know.



Yes you misunderstood. I mean after i hit the apply button nothing happens. Instantaneous non reaction. Collision visibility is on… it just doesnt even bother to calculate since its instant… i even try accuracy to full and max hul lverts 32… still instant with no output.

Okay, after some further testing I think see what the issue is. In the Details panel > StaticMeshSettings > CollisionComplexity > do you have ‘UseComplexCollisionAsSimple’ enabled?

If so, change that back to ProjectDefault to see the collision being created. I’m going to investigate further but I will likely enter a bug report for the collision not being displayed when ‘UseComplexCollisionAsSimple’ is enabled. However, the sphere, capsule, and box are all displayed. So it’s possible that the bug might be the opposite, that no collision is expected be displayed when it is enabled.

I’ll post back here with the JIRA report number once it’s entered.

That could be the problem, though im still trying to figure out which mesh i used during that moment i noticed it wasnt working. Only reason i need to figure that out is because it didnt even bother calculating… where as right now it calculates on another mesh but isnt visible as u said until usecomplexcollisionassimple is disabled.

Or maybe im remembering it wrong, but in either case as of right now its working when i disable use complex as collision. Thank you!

Auto Convex Collision generation requires that “Enable Collison” be checked under the LOD material element. I’ve responded similarly on your other post that covers this as well here: Collision not working on newly imported models without autogenerate collision first - World Creation - Epic Developer Community Forums

This was a deliberate change in 4.12 when Selective LODs for Collision Mesh were introduced.

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I was having some issues with no collision happening after converting a group of actors to a new static mesh.

Specifically, I was trying to use Auto Convex Collision and nothing was happening. I saw collision primitives on the mesh but no option to remove them, too. This was even after creating simple box collision primitives and selecting Remove Collision; the new box primitives would disappear but the primitives that existed on the new static mesh after conversion remained.

The solution for me was to do what TJ said: Details > StaticMeshSettings > CollisionComplexity, set to Project Default. Auto Convex Collision worked after that.

im now using 4.14.3 and its broken again. Collision is active in the lod… collision complexity is on project default… ive tried every setting in that drop down… The auto generate collision simply is not working at all. Any ideas?

Any freshley imported model simply cant use auto generate collision. Very frustrating.


I have created a new bug report here since the problem now goes way beyond not being able to auto generated convex collision… its developed into a crashable bug with repeatable steps… every time…

I was having this problem too, but this solution didn’t work for me. However, there’s another UE4 answerhub question that fixed my problem, here:


Make sure that you have “Enable Collision” Checked for all materials that you want contributing to the collision calculation of Auto Convex Collision.


That setting is checked, by default. I was scared though, and turned it off, because in collision preview mode all materials turned on will display a blue wireframe around the static mesh.

^Technically, this above image has no collision, as collision meshes have either a green or purple wireframe color.
I assumed that setting was to use per-vertex collision, but instead it is just to display which meshes will be considered when collision is generated. If “Enable Collision” is off for all materials, the Auto Convex Collision’s “apply” button does nothing.


Aye confirmed. Just ran into this issue. Have to make sure LOD has “Enable Collision” toggled on. Next to “Cast Shadow”


I’ve tried about every suggestion that I can and I still get nothing but a progress bar that seems to be hung up. Missing something?

Thank you!

Mac 10.13.6
UE 4.19.2

What are your default settings for the hull calculation? Maybe yours is set too high? It definitely increases the calculation time if the hull precision in increased. This is the standard:


A bit late but could be useful :

There is this funny bug : just click Collision > Remove collision, then uncheck “Customized Collision” (in Details panel). Now you should be able to generate the collision.

Don’t ask me why, It happened to me but I don’t understand lol. I simply clicked everything related to collision until it worked.

Funny thing is several people suggested this and I was searching for “Enable” in the details and wasn’t finding anything. Thanks for the screenshot!

Could be / should be a mesh imported with custom collisions (ucx) entries.

In those cases having the engine generate collisions could compromise the model, so in theory anyway, that would be a good reason to have you manually clear out collisions instead of just overwriting them.

The checkbox should become set when the import settings of the asset tell it to import collisions, I believe.