There are plenty of tutorials out there for coming up with new, random coastlines from scratch using Difference Clouds and Threshold in Photoshop. But what if you already have a coastline that you need to roughen up a bit? Give it more of a natural, organic, chaotic feel?
This is what I came up with (adapted from this tutorial – Old Guy Gaming – Realistic Coastlines Revisited). I’m sure I’ll be adding improvements to the technique as time goes on.
- New document (sample is 3000×2000, 72 dpi, 8-bit RGB)
- New layer, delete Background, draw coastline shape (the more random and chaotic, the better).
- Magic wand (Anti-alias off, Contiguous on, Sample all layers off, Tolerance 0) the land areas, Select > Modify > Expand selection by 5, fill with black.
- Control-click the layer, Select > Modify > Expand selection by 15.
- New layer, fill selection with white. Deselect. New layer between Layer 1 and Layer 2. Fill with black. Merge Layers 2 and 3.
- Filter > Noise > Add Noise (100%, Gaussian, Monochromatic)
- Filter > Blur > Gaussian Blur (2.0)
- Image > Adjustments > Threshold. Adjust slider to desired levels (important to leave enough white in the landmass so that the black areas aren’t contiguous).
- Magic wand an open water area. Manually add lakes to the selection, if needed. Invert selection. Fill with white.
- Magic Wand in the white. Create new layer. Fill with black. Delete or turn visibility off on Layers 1 and 2. (Optional: Delete Layer 2. Merge Layers 1 and 3).