When aligning terrains to selected shapes, the original heightmap of the terrain is not modified. Rather, the change in elevation is stored in an elevationDelta map and saved as a separate image file in a subfolder of the data project folder. That subfolder is named after the CityEngine scene.
The elevationDelta file is created or updated only when the scene is saved. If there is no change to the original elevation, the file is not created; if the terrain is reset, the file is deleted.
These files and folders should not be renamed or deleted. You can also modify the elevationDelta image file with an image editing tool to alter the heightmap with techniques such as blurring steep slope edges for better gradation and saving the edits under the same name and location.
To view the elevationDelta map file, right-click the file in the Navigator window and select File Preview. The following delta map stores elevation changes on a gradient (gray = no change; black = lower; white = higher):
