Tutorials
Architecture Detail 1
Adding Architectural Details to Otherwise Boring Rooms
Part 1 - Rounded Corners
This is not so much a tutorial, but more a guide to adding detail, and hopefully helps get your creative juices going so you can create your own variety and style. Let’s get started.
Rounded Corners
This is probably the most known way of adding some interest to an otherwise boring corner. It’s certainly evident in most of VALVe’s maps. There are many places that rounded corners can be implemented, for example: Door ways, corridor corners, room corners, etc.
To make a fairly simple rounded corner, firstly draft out a template cylinder, like in the screen shot. This cylinder is a guide for our Vertex Manipulation later on. 
Now add some blocks ready for Vertex Manipulation.
Now, simply Vertex Manipulate your blocks into triangles, so they line up with your guide cylinder. You will have to go to the smallest grid size to do this.
If you do not know how to use the VM tool, I suggest you check out some other VM tutorials first.
Now delete your guide cylinder and there you are a nice, clean rounded corner.
Notes
• In my opinion, you don’t need more than 4 sides for a small rounded corner like the example in this guide. Anything bigger, say 64 units or more, you should use more sides. That’s your own judgement, though.
• Make sure your guide cylinder is square; otherwise you’ll have a weird looking corner.
• It goes without saying, but make sure you func_detail these brushes together, to stop unnecessary face splitting.
• To texture your new rounded corner, select all visible faces with the texture application tool and select align to face. Then align the texture accordingly. Tweak as you need to.
-matteh