So i just built an arena similar to colosseum in rome using geometry, but i would like to make the edges on the geometry to be smooth. Is there a way to do this?
Edges now:
How i want them to be:
Cant find a good picture, but basically i want it to be less square and more round edges. They didnt have that precise tools when they cut the stone back then
As far as I know that’s not directly possible -> BSP brushes are mainly used to prototype your map. Everything else is done in a 3d tool like blender, 3d , maya,… 
You could add some more vertices in the geometry tool + then create a smooth edge -> but that’s easier in a 3d tool
Sticking a post processing volume and enabling anti aliasing should at least in theory help smooth out jagged lines in gameplay
I have seen it done on the Unreal Garden demo. I believe they made the corners look round using a normal map.
Tools for editing mesh geometry inside the editor are one area of development that is certainly under way this year (eg ability to subdivide meshes) but they are at an early, experimental stage so far and in the meantime you will either need to use tricks, 3rd party add-ons, or external modelling tools. The BSP brushes still work but have a number of drawbacks and will likely fade out of use for many scenarios as the new tools are released and mature.
We can play with an initial early version of the new tools using the special dev-geometry branch of UE4 available on github but this is really just to see where this feature is going, shouldnt be using it for production work yet really. And they wont be as fast to use for quick level prototyping as the current BSP stuff, especially if you make use of subtracting things to, eg, quickly cut doors in BSP walls.
