Workflow for building a level
We would start out by making a top down witch we used as a base when making the height map in Photoshop. We made the height map in Photoshop because we wanted the right measure between height levels when importing it into Unity's terrain tool.
In Unity we added props and painted out the splat map witch blends different textures in the terrain so we could create roads which are used to guide the player around the map. For triggers we placed invisible spheres with had a custom made script attached to it witch allowed us to write out a LUA function.
When the level was ready we exported the level to XML but the splat map and height map had to be imported into Photoshop for some additional adjustments before being exported into the game.
For path finding we used a tool in Unity that gave us a layout over the whole level but to make it readable and optimized in game we exported it into Maya where we removed unnecessary faces and exported it into the right format for the game to read.