How to uniformally divide a big single mesh into smaller parts?

Hello! I have tried searching for a solution to this question, but I suspect I am not wording it/using the proper terminology so I thought I’d ask for your help. Sorry in advanced if this is a semi common question.

I have a map that I imported as a .obj. It is a single, large mesh (monolithic I think is how you might call it?). I can’t import it into unity due to the vertex max count, which is fine. The object is 250k, the max I can import is 60k. Anywhere I read online suggests to break the .obj into different parts. I am not sure how to do this.

Ideally, I could break it into a grid. Ie: 3x3, or into columns/lines. However, I can’t find anything really reliable to do this. The best option I’ve seen so far is perhaps to scale a cube, add a boolean difference, and cut it manually. But this seems somewhat sloppy and also is pretty laggy/messy.

Any tips in the right direction or alternatives would be much appreciated. Thank you for the help and again sorry if this is somewhat common, I couldn’t find the right kind of tutorial when I used words like “divide, split, separate, etc.”

Select the faces you want to separate, and press P to get the separate menu. Choose “selection”. Do this as many times as you need to break the mesh down.

create a grid out of plane (mesh), then use for cutting… more > Knife Tool (Knife Project)
split/separate using box select
multiply mesh & then delete duplicated parts/areas
as you proposed boolean using cube array
mix all of the above

Kind of hard to point you in the right direction without a .blend file to screenshot the process, but if it has a mesh to it and not just one solid plane extruded down to make it cube like then you can select a section of faces both top bottom and sides and then use “p” separate and repeat as needed to get the object down to required sizes as mentioned above. If it is a solid plane extruded then you can use the knife tool and slice it where you need and fill the faces that need to be filled. You may have to adjust the uv mapping when doing these methods otherwise you might end up with a funky looking result.

Here is a little rundown just shooting in the dark here.

Selected the faces I wanted to make a separate mesh

Then pressed “P” and separate

Then filled the empty sections that were separated selecting the 4 verticies and hitting “F”

Then once done filling then you end up with 4 separate objects, but as I mentioned you may need to unwrap over again being the objects are not the same original object mesh.