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Merge Actor Tool - creating unnecessary "sections"

Hi,

I’ve only recently (today) discovered that most likely somewhere between versions 4.15 and 4.18, there has been a change in the way Merge Actor tool works and it’s a little inconvenient and messy at the moment. Whereas in the past (4.15 and before) you could merge a bunch of static meshes, which were using the same material, and you would end up with one static mesh and one element, now it for some reason creates quite a number of these elements (they seem to be called “sections” in 4.18) and each adds an extra drawcall. Now, the reduction of drawcalls is one of the reasons to use the Merge Actor tool in the first place so this feels very much like a step backwards.

The only way to handle it at the moment from what I could gather is to export the merged mesh and reimport it again, but that’s not exactly what I would call a solution because it can be quite time-consuming with a large amount of merged actors, not to mention having to reimport collision, mess with vertex painting, LODs etc… And while the engine can handle quite a large number of drawcalls, ignoring the issue doesn’t seem too ideal either especially when you merge 30 small objects and end up with a single mesh with 18 sections/elements (the number seems kinda random) all using the same material slot.

I’ve seen a couple of people mention this issue but there hasn’t been any solution apart from reimporting. Am I the only one bothered by this? :slight_smile:

Here is one thread with screenshots:

https://forums.unrealengine.com/development-discussion/rendering/1376757-actor-merge-does-not-groups-elements-of-the-same-material

Note that the first response by Raildex suggests removing material slot, which however is a different thing. These merged meshes have only 1 material slot and one material in it. It’s the sections on the mesh (what used to be called elements) that appear out of nowhere and just as magically disappear if you export and reimport the mesh (without even editing it in 3D software). Is there something I’m missing here? It would be ideal if the sections on the static mesh could just be merged together with a simple click, or even better, not created in the first place.

Thanks in advance :slight_smile:

I have the same issue and fixed this with reimporting mesh. But this is a bug indeed, cuz in 4.16 merge actors worked differently.