Hello,
I am working on a level design in Blender, which is pretty simple(walls, floor, window, door frames). For each wall/floor/etc. I created a duplicate and named it UCX_meshName. When I was finished I selected all the elements and their UCX duplicates and then exported the selected objects as FBX. I then imported the FBX into unreal without auto-generate collision and with the “Use convex hull per UCX” option disabled. The result was only a few(more accurately 2) of my models had correct collision while the others didn’t have any at all. I copied all the models in the same way, and double checked the names. I also compared those which worked to those that don’t, but I didn’t find any differences. Also, I should add an earlier version of my level was correctly bound to the UCX duplicates, but even those that worked before no longer work now. What could have I done wrong? Does UCX require a mesh without material slots/UV maps or something like that, even though that worked before?
Wireframe of all the UCX meshes:
Collision in UE4:
Import settings:
Thank you for your time,
suzi9spal
Hmm weird how only a few are working and not others, if all weren’t working then it might make sense.
I’m not a Blender user (more 3ds max) when I create UCXs in 3DS I do it with the naming convention - UCX_meshname_001 , UCX_meshname_002 , etc
If you add these suffixes to your UCXs does anything change on import?
No, nothing changes if I rename the collision meshes that way. I highly doubt it’s Blender’s fault, since it never behaved like this until now.
Would it be possible to upload the FBX somewhere to have a look?
The problem has been resolved. The issue was very unexpected though. After deleting an object in the level that had been rotated by 90 degrees in Blender, it all worked. I cannot explain this to myself, but since it works now I don’t even care 
I suspect that Unreal uses some kind of sine function do figure out the coordinates of a rotated object and might have encountered some kind of error(like division by 0) while applying the UCX collisions. Whatever the case, deleting the object and re-constructing it from scratch, faced in the correct direction fixed all the collision.
Thank you anyway QBert
Oh cool great 
Good to know also
