Flattening Roads

You can also specify the Flatten parameter in the overlay properties. If Flatten is set to True, the overlay will try to flatten the terrain underneath it.

However, when enabled, this option flattens road bumps along its width (from one roadside to another one). Along its length, the road may remain uneven. In other words, the road is flattened in a perpendicular direction. I.e., there will be no oblique slopes from one roadside to another (see screenshot below).

NOTE: The heightmap itself will remain unchanged when the Flatten parameter is enabled. The overlay will simply flatten it. To see the result of this flattening - you need to perform the Rebuild Terrain operation.