Combine Meshes without Overlapping UV's

Ok, so I have a Fridge that I’ve modeled in Cinema, each element is broken apart such as Door, Chrome Handles and so forth. I’ve got those meshes grouped under a null a 0 point and each mesh has two sets of UV’s. The problem is that if I wanted to bring this in as static combined mesh all of the UV’s stack over each other and cause the light map to fail.

If I don’t combine these meshes everything work’s fine. I would assume that my UV’s might have to respect each other in their placement, so when combined they merge correctly. But I was wondering if there was a way to avoid this type of work.

Thanks in advance.

Hi Pixelvspixel,

You go it! That’s exactly what you would need to do. If these meshes are combined within UE4 on import and the UVs are not laid out in a way that they will not overlap each other this will cause the overlapping issue you indicated.

If you’re going to combine you need to make sure they respect each others bounds by having their own unique spacing to avoid the overlap since their individual UVs will be combined into one once they are combined with the import.

If you have any other questions about it or need further clarification let me know, but it seems like you’ve already got a good understanding of how they affect each other. :slight_smile:


Hi Tim, I have the same problem Unfortunately I bought an asset with 3 LODs which are overlapping UVs on combine - I have 0 clue with 3D authoring tools - so I doubt I can fix it - but I can export each LOD as a separate FBX:
Question: If I will export 3 FBXs 1 as base and 2 LODs and add the LODs to the Base in mesh editor in UE4 will i still have the same Overlapping issue ?
or I just should research how to do this in Blender and reexport FBX with the tweaked UVs ?


This largely depends on how the UV was laid out for the base mesh. The LODs should all be using the same UV layout with only lower edge/vert count. You can go through the process of exporting them and getting rid of LODs (which you can simply do in the editor as of 4.14 without having to export everything). Sometimes it still takes tweaking in an external program for models though.

If you bought the asset on our Marketplace one of the submission guidelines requires a good UV layout for the lightmap that doesn’t have any overlapping faces. You may want to contact the seller and bring this to their attention to update the asset. This should be the case for any Static Meshes and does not apply to skeletal meshes since they do not use lightmaps.

Unfortunately for me I bought it from turbosquid :-(.

Sometimes a lot assets like this do require some setup and fixing when bought from other CG sources. There are some that are “Game-Ready”, but often these still don’t account for a lightmap UV that is good for UE4 or have a good texture UV that works well with our in-editor lightmap generation. There are some good free tools out there for UVs or even Blender with following a tutorial you can get by just doing a flat mapping technique in most cases to get something that looks good enough to be less problematic.

Yeah this was tagged as game ready but well I tried it with SceneKit and it was even bigger disaster :-))) all the model was just black. Unity somehow managed to live with this but still not perfect - some shadows were completely off.
I tried several blender tutorials it didnt help- now I am going to try to make Auto UV channel will update tomorrow if ot helped.

Bit honestly I encountered another model SM_PineTree from landscape package on MarketPlace (I think by Epic) and it had 87.6% overlapping UV when I migrated it to my project - however in landscape project I have no warnings about UVs and lighting.
I think I am missing something here.

Static Lighting and lightmaps can be time-consuming to get right, especially when learning because there are a lot of “gotchas” along the way that really just takes time and practice to learn.

If the SM_PineTree asset is from the Open World content we released this is expected. Those assets were taken from the Kite Demo that EPIC did for GDC 2015 with a specific design in mind. They were only intended to be used as movable actors because that project only used dynamic lighting so there was no need for lightmaps. Generally for things like foliage you wouldn’t want to have that be statically lit anyway because often in games or projects these will move and sway with the wind to some degree rather than just stay completely still. If static lighting was used the cast shadow on the ground wouldn’t look very natural sitting still while the tree moved. Often times the swaying is handled via the material and not actual wind assets although these asset were created with SpeedTree which can use the Directional WInd actor in UE4.

SpeedTree assets also have a lot of UVs with 1 still often being used for the lightmap but it’s just a matter of looking at the UV and seeing if it looks like a Lightmap UV compared to a texture UV.