Making mountains

The mountain peak overlay is made from a reasonably rough 128×128 or 256×256 fractal (depending on desired size). This fractal is made by a modified diamond-square algorithm in which the edges smooth to zero such that no seams are visible when it is overlaid on the heightfield.

A mountain generated by the 'Mountain' special overlay.

Note that you do not necessarily need to put down a special mountain overlay to get a mountain peak. You can get quite nice mountains just by setting the 'alt' and roughness parameters in the design map. Below is a mountain generated by just such a procedure.

A mountain generated only by inflation of the design map 'alt' values.