Good work Unity, finally it’s here and it seems to work perfectly (just tested it).
Been waiting for this for quite a while.
Thanks !
I didn’t even know this was coming out in 4.3. Can you give any more information on it. Like does it allow you to modify the navmesh during runtime (for building placement in rts)?
And especially, do Unity free users have access to it?
I don’t know about Unity Free, i’m a Pro user.
Yes, it does allow to modify the navmesh at runtime.
You just use a regular Navmesh Obstacle as before, but now it has a flag “Carving”, which when it’s on, if you move around that Obstacle it modifies the navmesh at runtime.
You can enable it or disable the carving 
So yes, it will work perfectly for rts’s and building placement.
Think it is a pro only feature:
"Unity Pro’s Navmesh functionality just got much more sophisticated. You can now alter the Navmesh dynamically at runtime with obstacle carving. What’s more, thanks to dynamic offmeshlinks, the user can visualize new ways of getting past those obstacles: If the bridge is down and you fell a tree to span the gap, Navmesh can keep pace with the action.
Iterating your offmeshlinks is easy. There’s no need to bake and repeat – Unity takes care of all your updates automatically so you can see your changes as you make them."
I see, thanks for the info. I’m planning on getting Unity Pro when I can, but for now, it’s cool to know it’s in the editor
I’ve tried the NavMesh method for a few months however it’s limitation is that in 4.3.4f1 the NavAgents using the NavMesh will stutter and pause with their movement and also some of them completely stop moving when a Carved dynamic object moves. I’m now using ‘Dynamic Navigation’ in hope to overcome the dynamic obstacle issues however the problem with this asset is that it’s messy. Components everywhere and the pathfinding isn’t as smooth as the Unity Navmesh. It also requires a unique way of using layers which gets in the way of how you want to use the layers.
With obstacle carving, you can only create solid blocks / holes carved into the mesh. This means if you want to create a maze / house etc dynamically, you would need to create a hole for each wall. This will cause any moving objects to momentarily pause or fail. This can be fixed by sending them a command to move to location X again.
Tested the same situation with Aaron’s A* and it does not cause a pause or failure if you move a carved object during runtime. Which leads me to ask “if it’s possible, then why doesn’t unity improve their code to do it too?”