(Unsolved) Unions cause model to deform

Howdy, I’ve seen some similar posts regarding this here on the DevForum, however no solutions have worked for me.
When I attempt to union my bus model, it does some weird deformations all around the bus that cause some of my smaller details to not be visible. It seems to add some material on the front and remove some in the back, but it isn’t moving the bus forward (if that makes sense?).

Front: https://gyazo.com/b7f314f8c3dc8a912b1338b81c012b8e
Mid: https://gyazo.com/841a40c61ab2fa59e90ed2a8ddb693b6
Back: https://gyazo.com/11c2246504095cd8f1a1514b56720116

It doesn’t matter which Negative part I select to union with the bus union, they all have the same result (even if I select multiple Negative parts to union).

I’m currently using CSG v2, although I tried switching between the two with no difference in the result.
I’m pretty confused and don’t want to have to remodel a large portion of the vehicle. Any help is appreciated.

As of now, you could try a simple restart:

  • Duplicate the bus (Don’t negate it yet).
  • Save or publish to Roblox Studio.
  • Restart Roblox Studio.
  • Then negate the bus.

Sometimes, a simple restart could fix weird union glitches or errors.

I’ve never personally encountered your error, so this is all I can think of right now.

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I’ve tried this several times to no avail. Seems like more of a bug issue, however, I can’t post in the bug reports category.

Have you tried making a new baseplate (by this I mean a new place or experience), then pasting the bus and negating there?

Just tried this, it still didn’t work. It seems that whenever I union something with the bus, no matter if its negative or not, what size or position its at, etc., it still deforms. Not sure how to go about this outside of remodeling the bus and hoping the same thing doesn’t happen.

To me it seems like there’s an issue with the complexity of your Union. How many Tris are in it before and after you do this operation?
Are all the Union and Negate Parts Anchored? If not try that and see what happens.
It’s hard to tell from the videos, but it just seems like the entire Union is moving forward about .2 studs. What happens if you copy the Position of the Union where it is supposed to be, negate it, then paste that value back into the Position?

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The TriangleCount property isn’t loading, so I’m not entirely sure. I tried all possible fixes you mentioned and none of them worked. This seems more like an issue for a bug report, so I’ll file one later once I become a Regular member.

Luckily, I backed up my place prior to separating the bus, so I have a fully unioned model that looks fine. I separated it originally to fix some symmetry issues that I suppose I’ll have to live with until I feel like remodelling or this bug is fixed.

Have you tried exporting the Union to Blender to fix it?
I know it can be a bit intimidating at first but Unions really are not great for complex shapes. If you ever export even a simple Union to Blender you can see many more vertices causing many more tris than are necessary.
I’d say your bus is pretty complex, so I can’t even imagine how many vertices the Union would have there.

I’ve had this issue before. It boils down to the complexity of the model. The more complex it is, the higher the likelihood of the union not turning out well.

I’d suggest make smaller components and welding them together.

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