Invisible Unions

I get these extremely often and for that reason I stray away from unions due to their unpredictability. Why do they go invisible? And how come when I turn the invisible union into a negation, it appears (but red)?

How come when you make it negative it can render but not when it’s a union? Very confused.


That was happening to me yesterday. I think it’s caused by a combination of play/reset and undo/redo.

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Did this recently start happening? Could you post a place with one of these unions?


I’ve had this happen just in Studio, but reopening the server/player fixes it. And it’s really inconsistent - most of the time it loads just fine.

I think it has something to do with the rendering, I moved an invisible union, and it re-appeared

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Yes it recently started happening.

I don’t have a repro right now, but it happened, as ArceusInator said, with unro/redo attempts. Also when you press CTRL-S they often disappear and pop back up right away. It’s just kind of sketchy how that happens.

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I can explain this, at least. It happens when it sends the mesh, physics, and child data to ROBLOX’s servers to be streamed. Apparently when it does this it reloads the mesh from the asset URL which is why it disappears and reappears.

I noticed this about 5-6 months ago. I’d Union some Parts or Parts with a Union and it’d disappear.
Either that or try to copy the Union and either the original or the copy would disappear.
Other than reloading the place I couldn’t find any other way to fix it.

One of the reasons I’ve given up on Unions. For now.


It was mentioned, but I’m fairly sure it is a result of saving or doing a process that alters the UnionOperation. EX: if you play around and make a complex union, then undo a few times, then redo, then undo again, sometimes the union’s mesh will improperly load or render, resulting in an invisible Union part. When you publish a game/place with multiple unions, ROBLOX saves the mesh data and then reloads the mesh data sometimes taking a few seconds and making unions briefly meshless while the mesh is loaded.

Question for people who’ve seen disappearing unions: if you right-click a union in the Explorer window (and only in the Explorer window) one of the options that comes up is ‘Recalculate Mesh’. Does this make the union reappear?

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Didn’t know that was a thing.

Today I’ve just been experiencing many MANY crashes when trying to use unions.