With the most basic terrains (oceans and plains) out of the way, it’s time to tackle the more complex overland styles. Forests and jungles are visually very similar styles. Jungles are slightly more complex so we will focus on approximating its style first and then adjust the style to fit the forest coloring.

Shape

We’ll start with the “self-imposed”, but still importent problem of area shapes. So far we have smoothed the outlines of jagged svg paths to get a more pleasing shape at different zoom levels. In the case of jungles and forests, we actively want to deviate from smooth curves by adding some blubous protrusions. By adding these outline details with a filter, we will be able to add outline freatures at higher zoom levels without having to change the svg path. A simple way of achieving the effect is to add a turbulence pattern to the blurred outline before thresholding with a color matrix filter:

Background Gradient

The green background color of Jungle terrains features a slight random color gradient between blueish and yellowish green tones. We can simply recreate this with a large turbulence pattern and a component transfer filter on a single channel of the resulting noise pattern. In the component transfer we use the table mode to define blue-green (#) on one end, yellow-green (#) on the other and the average jungle color (#) as middle value. This provides a color transition roughly equivalent to the target image. It does not capture the slight bias towards yellow around rivers, but that is a detail i am willing to ignore for now:

Outline

The brown jungle outline can be created just like the coastline, by using morphology filters to grow and shrink the filtered shape by small amounts and coloring the result (#).

Border

The border area of jungles and forests has two main components. A brownish inner glow, that roughly follows the outline but has some distance and color variation, and a dense coverage of random dots. Starting with the background glow, we can use the strategy used to generate the coastal shelf with a narrower width but more randomness, leading to following result.

Dots

Jungles have a dense outline of dots in the border area, but also small groupings of dots throughout the entire shape.

Forests

The forest terrain has the same general features as jungles with some color and density variations. Basically, the background is solid green and the width of the border is slightly more narrow:

Up next we will take what we have done so far and try to combine it into a preliminary map.