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UCX on boned models not generating on import


I'm trying to make a animation for a mechanical door. Unreal Engine 4 does not have vertex animation yet (that I'm aware of) so I animate the door with joints in Maya.

The model imports with no errors. The animation plays just fine.

The problem is, the UCX_meshes does not generate collision geometry when imported. It appears as visible meshes. I've tried naming the UCXes by "UCX1_mesh" and "UCX_mesh_01" but neither work when the imported asset is boned.

How can I make UCX collision meshes work properly on meshes with skeletons?

First image: Asset is boned and UCX doesn't generate.

Second image: Asset is NOT boned and UCX generates.

does not work

is working (while asset is not boned)

Product Version: Not Selected
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asked Dec 07 '14 at 09:59 PM in Using UE4

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avatar image atomicFunkdog Dec 08 '14 at 06:06 PM


It seems not to be a problem with being boned. The problem is when Imported as Skeletal Mesh. When done so, the UCX does not generate.

avatar image Diaval Jul 30 '17 at 08:08 PM

IMO, this is a flaw that could be easily fixed in the Engine. (I have worked as a technical artist with UE4 for well over a year and am well aware of the problem and the possible workarounds.) What should be happening is this: On import meshes named UCX_[BONENAME]01 / UBX[BONENAME]_01 etc. should be assigned to the corresponding bone in Phat (and unassigned bones should get default collisions or no collision and you would make that choice on import). 99.9% of the time I generate a Phat on FBX import only to then delete the default collisions and to generate new ones. I am not exaggerating when I say the system-fix as I am describing it would save me at least 80 hours of work in the next month alone (including the time it would take me to make the collisions in another program).

A basic example where you do want this kind of control, is a complex character, or a vehicle. Your character will need special collisions here and there. Not everything can be handled by capsules. And putting special collisions in your BP is not compatible with Phat constraints etc. And even assigning the capsules would be much much easier in your 3D program of choice.

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Hi Christoffer,

I see you were given an answer on the forums for this issue: https://forums.unrealengine.com/showthread.php?53825-UCX-not-generating-when-importing-as-Skeletal-Mesh

"Skeletal Mesh cannot contain UCX. Collision mesh need only for non Skeletal mesh. For Skeletal Mesh you need generate Phisycal Asset (automatic when importing the object or manualy after import). Read this docs... https://docs.unrealengine.com/latest...hes/index.html"

This is correct. For meshes that use bones you'll be able to create physics assets for the collision. However, for something like your machine example this may not be the ideal method, assuming you need more accurate collision. In this case it would be more prudent to use Blueprints and setup some animations and movement that way. This ensures that your mesh can use UCX meshes for it's collision shape.

Thank you!


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answered Dec 09 '14 at 03:14 PM

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Tim Hobson ♦♦ STAFF
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avatar image atomicFunkdog Dec 09 '14 at 08:03 PM

Thanks, Tim. I'll give that a try. By the way, would you know if importing UCX meshes though skeletal meshes will be possible in the future?

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