I want to build a somewhat simple interior

Tofi

I'm an experienced 3D artist but I've never had to deal with building a level inside a game engine so I'm trying to change that.
Would it be feasable to make the walls as one single mesh? And if I were to make the walls modular how would I avoid the texture seams? (I'm actually very curious about this one)
Also I'm not entirely sure why it's done modularly. Does it decrease the performance by that much?

AlexG_WoLD

You have a lot of repeating geometry. Modular meshes would be your best option.

To avoid texture seams:

• you could make your texture tileable
• you could create certain sections of the wall as a single continuous mesh
• you will experience lightmap seams between modular meshes if they are a clean flat surface, so you'll need to utilize texture or geometry variation to hide them or not use baked lighting
  
• you could break up certain parts of the walls with columns or texture trims
• you could use vertex color

Modular meshes improve performance, it reuses your textures/materials. It doesn't make sense to create that as one single mesh. You could but modular pieces would be actually be less work and better for performance.

More here: http://wiki.polycount.com/wiki/Modular_environments

Tofi

Thank you for your answer!
From my point of view, it seems more work to model 10 types of modular plain walls and make sure there are no obvious seams when texturing, than making it into one mesh, following the plan correctly, and aplying tileable textures with no issues.
The performance, though, is something I need to keep in mind. 

Decency

I wouldn't bother making the walls modular, there aren't enough to be concerned about it in this scene.  You won't have texture seams either way as long as your texture tiles well.  Also for this type of work, I'd look up Datasmith and use that workflow as it can make your life a lot easier.