I am making a very narrow strip of terrain, about 250 units deep on Z and 10 - 15 units deeps on the X. The problem I’m running into is it seems Unity scales the brush to the terrain so if the terrain isn’t a square, neither is the brush. This is making it very difficult to make smooth holes/hills in my terrain. Is there an option in Unity to disable terrain brush scaling?
As far as I know, Unity terrains always have a square heightmap, even when you set different scales to the X and Z axes - that’s why the brush gets scaled too. If you really need it to be a strip, maybe a better solution could be to create a mesh in some 3D editor, import to Unity and use it as the floor.
Another alternative: create a equally scaled terrain, then rise the strip you want to some height (say, 50) and edit it the way you want. In order to hide the low part of the terrain, you can create a plane below this height to simulate water, or other thing you want. A good way to rise this strip is: export the heightmap (menu Terrain), open it in Photoshop, paint the strip as a gray rectangle, save it in RAW format and reimport it to Unity using the option Import Heightmap - raw….