River

A river is a common aquatic biome that cuts through most land biomes. Rivers can serve as borders between various other biomes, and usually lead to oceans, although they are also able to form loops.

Rivers generate in land whenever the PV values are on their lowest; in the deepest part of valleys. River generation does not depend on temperature or humidity, meaning that they can cut through any type of land, but they are replaced by frozen rivers in the frozen temperature zones.

The shape of rivers is determined by the PV noise. They always twist around higher landmasses, sometimes they form loops that can be small enough to have no land inside.