What's better for game's performance: Union's or Parts?

So,

I’m creating a couple of maps with some high details. Now i’m wondering if it’s better to use 25 Unions VS 200 parts.

Better in perfomance, such as playing on the maps without lagg.
And, do Union’s take longer to load then Parts.

Anyone in here with ‘scientific’ proof, for example a Roblox article.

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Use parts since they are primitives.
The ram usage is more important that a few more triangles to render.

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I would do some research into instancing. Using meshes from blender and using them over and over is a great way of making a game look really nice while keeping performance high due to instancing.

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Don’t use unions. The mantra you should learn to repeat every time you wake up, go to bed, brush your teeth, or blink.
In seriousness though, unions are often unoptimized and therefore bad for performance. For optimal performance, you would want to make your maps in Blender, but that isn’t exactly easy. I would stick with parts if you don’t want to learn 3d modeling software.

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short answer: parts

I don’t have any proof for you, but combining a bunch of parts into a union doesn’t seem like a lag strategy. The geometry will still be there, and as other have said, you are probably just introducing additional work for the rendering since the basic part instances are optimized.

I would not agree to ‘never use unions’ but the reason to use them should not be related to lag. I’d only use them if you need them for a custom shape that you can’t get from the basic parts, or when you need to have a material pattern look better spanning across multiple adjacent parts.

25 unions made using total 200 parts than 25 union will require to more load time and collisions generations but since parts are pre loaded in roblox they will quick load.

Only use UnionOperations for one-time-use objects that are moderately complex. For example, if you want one of your windows to be shattered and it’s easily do-able with UnionOperations, go for it. However if you want multiple windows to be shattered in the same way, it’s best to create it in Blender as a MeshPart.

Now for the MeshPart versus Part debate, it really depends on tris count, a statistic you can also see in Blender. Whichever has lower tris should be used. If parts have lower tris then you also have the benefit of having slightly faster loading speeds.

Use parts when you want basic objects such as floors, walls, basic fences, etc. Use MeshParts when you want a little more detail on your models, like bushes, plants, etc. You should really never be using UnionOperations. It’s easy to use of course, but they create unnecessary triangles which in abundance can lower frames per second.

I also think if you provide an image of your unions, I can choose the most performant option for you.

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I would choose parts, but fun fact, did you know you could save this 200 parts as meshes, then load it into 1 mesh and kaboom. The most optimized right?

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