How to split objects

[Jon.Topps]

I'm not even sure how to ask this, so bear with me. For reference, think Fallout Shelter.
I want to create a whole object, in this case, the surface of the ground, then about 60ft below the ground. I basically want to create a slice of the ground, that you view from the side, which the player will eventually dig out, and create rooms in. What I want to do is create the whole area of the ground, with rocks, roots, fossils, etc. that will look good from the side, and then I want to divide it up into pieces, so that the game engine can eliminate the rectangular sections of ground, switching them with rooms.
So like, I make a huge area of ground (I can do this easily enough), and then break it up into 4x5 rectangular rooms, all of which have about a foot in-between that will remain ground all the time. So it is basically one object that is a big grid of ground, so rooms/dirt can be in the slots, and then 20 rectangles of dirt that are all separate objects. As one piece, it will look coherent, but it's all separate objects, so that I can delete the bits.

Does that make sense?

Basically, I want to know how to crop whole sections of an object, making that section a new object.
Any ideas on how to do that? Thanks!

[Jon.Topps]

Thanks, but yeah I don't think that will work. What I'm talking about would be creating tons of new vertices/edges/faces. I want to split right down the middle of some faces.

At the moment, I'm thinking of using the boolean modifier. I'll create a cube the size I want the rooms, then make a duplicate of the whole ground object, and remove areas of it using the room sized cube. Then, with the ground object with holes in it, I'll boolean the original ground, which will create a bunch of room sized rectangles of the ground.

Two problems I'm thinking will happen.
1 = I need to separate each of those room rectangles into their own objects, which I don't know how to do.
2 = The big issue here, boolean seems to have massive problems when vertices/edges/faces have the same coordinates, and it causes really stupid buggy problems, so if my ground objects are overlapping, minus the missing holes, I'm guessing it won't work.

[still__alive]

I don't think you should be looking to separate one larger objects into smaller objects, I think you should start with smaller objects and use the extensive snapping options to position stuff.

Basically make a bunch of modular pieces that you can show, hide, or swap in and out or whatever as you need them, in the game engine.

https://www.youtube.com/watch?v=5bY3mmBunpo

https://www.youtube.com/watch?v=T8hGKsf7eXA

[still__alive]

This is just a very quick and dirty demonstration that I threw together in a couple minutes, just to give a visual demonstration of what I'm thinking of.

https://steamcommunity.com/sharedfiles/filedetails/?id=2023876360

https://steamcommunity.com/sharedfiles/filedetails/?id=2023876792

Sort of like this, in your specific case. Make a vertical plane or whatever for your dirt object, and cut "windows" out of it that are the size that your rooms are going to be. Make your various rooms, and in the game engine when you build a new room or whatever you put it behind the "window" then remove that tile from view or delete the "window" object, or whatever.

With the various snapping options, the 3d cursor, and the array modifier, it is pretty easy to start with multiple objects but easily and quickly line them up. A little out of the box thinking helps too.

For example, I could make an 8' x 4' sheet of plywood with a single plane with 4 verts, and I might want my final geometry to be the same. But, for purposes of staggering multiple sheets of plywood I might go and just throw an extra edge loop right in the middle of that plane PURELY for using vertex snapping to stagger multiple sheets of plywood, then delete that edge loop later on. As in I'll add extra geometry just for snapping purposes and lining things up, and later remove that geometry if I don't need it for anything else.

Oh, and when you are in edit mode, you can select vertices, edges, and faces then hit "P > Separate by selection" which will separate your selection out to a new object.

Basically I made my room from a cube, added the monkey to give some visual depth for the screenshot, and then used an array to generate duplicates, then I selected and separated them out into their own objects with that P hotkey. Then I put the plane in front, added edge loops and used vertex snapping to put the edge loops in line with the gaps between the rooms and separated out the "window" parts with the same P hotkey.

[still__alive]

So my overall point is do something with modular pieces, and use Blender's snapping and positioning options to help you line these modular pieces up while you are designing them to keep everything looking good. Then in the game engine you swap pieces in and out as you need to.

[Jon.Topps]

Cool I think I get it thanks. I'll have to mess with the array modifier, haven't had to use that too much yet, so I'm not familiar with it. Thanks!

[Jon.Topps]

Got a little bit used to the array modifier, tried it out a bit. Still have to join things and make them game objects, but this is what it's looking like.
https://steamcommunity.com/sharedfiles/filedetails/?id=2024966073