Usually when I’m working on a prop I’m used to hiding the grid to clearly see the objects, but when you are creating modules, the grid’s one of the most important things you have to take care of.  Every piece has to be aligned with the grid.  This is the first rule for me.  The second one is that you have to create the module, trying to avoid the seam with themselves and to do that there are thousands of ways.  In my case, I chose to hide the seam with other modules, or joint them in the dark areas, for example, in the cavities. 

There is always a workaround if you can’t.  For example, for the decals over the seam, use a tileable texture along with the module, and hide the seam with the darkness etc.  Another important thing is to take care of modules, it’s the ratio of the pixel per centimeter, because if you create the UV of every object in the scene with different density, the pieces don’t blend very well.  The pros of using module pieces is that you are able to create an infinite number of different environments, just using a few models, so, obviously it’s the fastest way to create an environment. 

The scale of the scene is managed by guessing.  I’m joking.  Lol.  First of all when I start to create an environment, I always build up a block mesh.  Block mesh is just a simple mesh with the biggest volumes, that helps you to walk into the environment and make sure that everything is fine.  When everything is perfect you just have to recreate some part of the blockmesh with definitive modules, that’s how I managed the scale of my scene. 

Picking Up Unreal Engine 4