Roblox developers will most likely be aware of one of the three solid modeling operations that are possible to do using the tools provided, which is union.
One serious concern for people is the fact that many players have reported that having too many unions in their game has caused their Roblox game to lag. If you're experiencing lag or low fps, even in regular games, then check out our guide on how to improve FPS in Roblox.
Can Unions Reduce Lag?
In no scenario does using unions reduce lag. On the contrary, having too many unions can cause potentially lag. However, reducing the number of unions also reduces the number of hitboxes and collisions that have to be rendered, reducing the performance problems. That doesn’t necessarily mean you should delete them all, as you can still use some of them.
If the reason you're using unions is that you want to form a complex shape, then we recommend making that shape in blender as a mesh instead of a union, since not only will it be easier to adjust it, but the mesh will also give you more control and freedom when it comes to removing unwanted textures.
Finally, if you're done with all the creating and want to publish your game, then here's how to publish a game in Roblox.
How Unions Cause Lag
Before knowing how unions cause lag, you first need to know how they work. When creating a union, Roblox will generate it in triangles so you will be able to visualize what the object looks like.
However, again, if you're a Roblox developer, then you'll already know that Roblox isn't perfect, especially when it comes to their creation software. Due to this, it ends up creating unnecessary triangles, which end up getting rendered, causing performance problems and lagging.
This, in addition to the fact that they normally have extra faces or an unnecessary amount of vertices, makes unions the worst performant when pitted against models and meshes, all of which are tools used to meet similar results.