For an on-going project I produced a series of customisable modular assets that a level designer could easily use to block out new maps. The current system we were using led to unreliable wall heights, widths, irregular doors and was causing each level to be significantly different in terms of design and gameplay.
Here is an example of the simple meshes aligned together to produce a corridor, you can see how the level designer can easily make windows, doors or double doors visible at the click of a button. This makes the design process so much faster for getting the main gameplay down for a level, once this is done the data can then be exported to a 3D modelling package so assets can be designed to fit perfectly within the space designed previously by the level designer.
This shows the progression of a level ten minutes after the initial corridor, using the grid align function in Unity allows quick snapping of the pieces and converting the meshes to prefabs speeded up the process.
Beginning to get more creative with the level design I decided to use some of the door frames as windows on the second tier, and giving multiple rooms different heights.
Be Finally I applied some basic texture to the walls to help define the area for testing, I also integrated some of the mechanics such as the warrant doors (which now make a lot more sense giving two access points).