I made a video to show how to split an item into multiple collision boxes, letting you walk through gaps etc. My demonstration uses an arch I initially added but of course couldn’t walk through, till now.
It really is as simple as taking your final product and hitting Y to split the mesh and P > Selection, to make a new object, which in turn makes a new collision box.
Hope this helps someone!
Also, I’ve seen other models made that you can enter but they are extremely laggy, I’d recommend keeping it to a minimum.
You can! But I’d like to point out that it gets laggy, there are already a couple apartment buildings in game that someone made but they have a ton of individual cubes, and the FPS drop is significant. I’d recommend splitting objects to a bare minimum, only doing what needs to be done like my arch way.