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FBX cannot import LOD groups with more than one mesh per LOD level

The most non-descript error happens: "Unable to create asset 'path'". Tracing through the code it's because it expects every child of the LODGroup node to be a mesh. This is not the case if you have a LOD level consisting of multiple meshes, in which case the children of the LODGroup node will just be group nodes for each LOD level, with meshes inside.

Also, regardless if you import LOD levels one at a time from different FBX or via a LODGroup FBX, it will not "merge" materials with the same name or _skinXX suffix. So if i have 15 materials used total, but each LOD level uses some selection of say 8 of them each, and i have 3 LOD levels, the final static mesh will have slots for 24 materials once you place it in the world, some of which are the same material, and it doesn't respect the _skinXX order (as first LOD0 materials show up, then LOD1, etc). It's super important to me that the ordering of the materials be preserved across LOD groups, as i am programatically setting them.

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asked May 07 '14 at 06:26 PM in Bug Reports

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avatar image Lovecraft_K ♦♦ STAFF May 13 '14 at 06:57 PM

Hey Tansien -

I have not currently been able to reproduce this as you have described it above. Would you be willing to share your Maya file with us so we can track down this problem and try to find a solution?

Thank You

-Eric Ketchum

avatar image Lovecraft_K ♦♦ STAFF May 21 '14 at 02:39 PM

Hey Tansien -

I haven't heard from you, so I am going to close this post, but if you are still having the issue please comment and we will re-open.


Eric Ketchum

avatar image Tansien Jul 07 '14 at 07:32 PM

Please re-open, still an issue

avatar image Tansien Jul 05 '14 at 09:47 PM

Please re-open this, as it's still an issue in 4.2 Here's a FBX file exported from maya that uses multiple meshes per LOD group: https://images.sshnuke.net/it_rest01_maya.fbx (hierarchy: https://images.sshnuke.net/2014-07-05_23-47-21.png) Please note that the import only fails if you check 'IMPORT LOD GROUPS' in UE4, otherwise LOD0 gets imported just fine (but obviously I want all the LODs imported at once, otherwise I wouldn't care about LOD Groups).

avatar image rajkosto Jul 06 '14 at 01:50 AM

I'm having this exact problem too, its really cumbersome doing LODs one by one in separate FBX files. And the materials indeed do not merge so you have to change the same one multiple times (one per LOD) on each instance.

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Hi Tansien -

We are aware of this issue and a request has been inputted to try to get this fixed. I do not have an ETA for you as of yet, but I will keep you informed as we progress.

Thank You

Eric Ketchum

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answered Jul 07 '14 at 08:50 PM

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Lovecraft_K ♦♦ STAFF
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avatar image rajkosto Jul 13 '14 at 03:50 AM

In addition, a FBX with only one mesh per LOD level seems to hang my 4.2.1 UE4Editor.exe https://images.sshnuke.net/coatmaya.fbx hierarchy: https://images.sshnuke.net/2014-07-13_05-49-20.png ('Import LOD groups' needs to be checked, of course)

avatar image Lovecraft_K ♦♦ STAFF Jul 14 '14 at 02:34 PM

Hi rajkosto -

Thank you for your report. This also does seem to be a bug on the number of allowed LODs. I have put in a request by our engineers to review. In the meantime, could you remove one LOD level from your group and see if the model imports correctly? I just want to confirm that the issue you are experiencing is the same I have found.

Thank You

Eric Ketchum

avatar image rajkosto Jul 14 '14 at 10:33 PM

Yes, the version of coatmaya.fbx where I delete the last LOD level imports properly. I switched to 4.3 preview (on CL 2201842 atm), and it seems that now, when you uncheck 'Import mesh LODs' on this asset, it will import ALL the lods into the resulting StaticMesh, not just the first one, which was the better behaviour.

Also, I have this skeletal FBX, which makes the editor infinitely spin on "Processing Mesh Triangles" (it doesn't like a LOD level not having a mesh attribute or the mesh attribute having 0 verts/tris, which is necessary if you want the mesh to dissapear for that LOD level) https://images.sshnuke.net/GM.moa.child1.fbx (hierarchy: https://images.sshnuke.net/2014-07-15_00-32-54.png), unchecking 'Import Mesh LODs' still imports only the first LOD level properly for SkeletalMeshes

avatar image Lovecraft_K ♦♦ STAFF Jul 15 '14 at 04:20 PM

Hi rajkosto -

Thank You for confirming that for us. I will looking into the Skeletal Mesh issue. and get back to you.

We are trying to make AnswerHub posts as easy to read as possible, so a clear Question and a clear answer, so, in the future, please post each new incident as a new Question post.

Thank You

Eric Ketchum

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