World and levels › Terrain
What real land looks like
Know first: Landscape: terrain from a heightmap
Mountains, valleys and coasts look the way they do because two sculptors work on them at once. One lifts the land. The other breaks it down and carries it away, and water does most of that work. That explains why rivers join like the branches of a tree and why a lake exists only in a bowl. It accounts for the loops of a river, the flat floor of a glacier valley and the constant slope of scree. It also explains why hills made with a brush or with noise look like clay, and how terrain generators imitate the work of rain and time. This is the eighth lesson of the course “Your own open world.”
Why this matters
A beginner opens the editor and sculpts hills with a brush, or lays noise over the ground. From above it looks fine. But walk across such land, and something is off:
- the hills are round and look alike, like molehills or lumps of clay;
- there are pits between the hills: if it rained, water would stand in them for good;
- the valleys are not connected: you can’t walk from a peak to the sea without climbing again;
- the slopes are equally bumpy everywhere, at the top and at the bottom, where in nature there is a flat meadow;
- there is no flat ground at all: nowhere to put a village, a field or a road;
- cliffs and scree stick out at random.
The eye spots a fake even when it can’t say why. Everyone has seen thousands of real slopes and remembers how they are built. All of these have one cause: brushes and noise know nothing about water. Real land was shaped by water over millions of years. Water always flows downhill, gathers into streams and rivers, cuts the ground where it runs fast, and drops its load where it slows down.
Water leaves its traces everywhere, so real land reads like a story: where the water went, where it cut, where it left its load. This lesson teaches you to read that story. Once you can, you will see what a terrain generator does, what to fix by hand, and why a beginner who sculpts land with brushes ends up with nonsense. The lesson on landscape gives a short version of this; here is the long one.
The whole lesson rests on one picture. Pile a mound in a sandbox and water it with a watering can. The trickles join into little streams, and the little streams cut channels. The edges of the channels slump. At the foot the water lays out a fan of sand, and a small pit fills up and spills over its rim. You can see almost everything that follows in that sandbox. Real land is the same sandbox, except that the mound takes millions of years to pile up and the watering can is the rain.