Heightmap layer operations
A number of useful operations are available when the Selection button is active (click to toggle the Selection mode). You must have something selected for this to work, a small + will appear to indicate you can navigate the selection.
Merging a heightmap
If we need to blend multiple layers together we can merge them together using a layer operation. Merge with previous will blend the layer you right-clicked on with the one directly below it.
Flatten down
This merges the combined result of the stack down into the bottom-most layer and removes all heightmap data except for the bottom layer.
