Coastline deform

The Coastline Deform tool in background edit mode regenerates the land-to-water boundary inside a selected area. It works on both generated and hand-painted terrain.

How to use

1. Select the Coastline Deform tool in background edit mode.

2. Drag over an area the coastline passes through, in Rectangle or Lasso mode.

3. Adjust the sliders in the right panel. The result previews live on the canvas.

4. Press Apply to commit, or Cancel to restore the original terrain.

Sliders (right panel)

Control	What it does	Raise	Lower
Grow / Erode	How far the coastline expands or recedes	Land expands outward	Water cuts inward
Roughness	How jagged the coastline is	More small indentations	Closer to the original outline
Smooth	How much small bumps are cleaned up	Gentler, smoother coastline	Closer to the original outline

Other elements

Element	What it does
Rectangle	Selects the inside of a dragged rectangle.
Lasso	Selects the inside of a freehand loop.
Apply	Commits the change. A single undo reverts it.
Cancel	Discards the change and restores the terrain.

The effect fades toward the edge of the selection, so the new coastline blends into the untouched terrain around it.

Heights are adjusted along with the reshaped coast, so on maps with contours turned on the lines stay consistent with the new coastline.