Landscape: terrain from a heightmap

Ground in a game is not a sculpture. It is a regular grid of points, and each point has a height, stored in a gray picture. This lesson shows how a picture becomes ground: how many meters lie between the points, how many centimeters separate one height level from the next, and how it looks on screen. It explains why the ground is cut into pieces and how it simplifies in the distance without cracks. Then it shows what brushes do to the height numbers and how roads and water edit the ground in their own layer. It ends with what a heightmap cannot do at all. This is the seventh lesson of the course “Your own open world.”

Why this matters

A beginner opens the editor, picks up a brush and sculpts hills as if they were modeling clay. An hour later the hills come out round and all alike, like molehills. A gentle slope shows steps. A footpath will not dig in: it smears into a wide hollow. A rock on a slope hangs in the air by one edge. And an overhanging cliff or a cave entrance cannot be made with a brush at all.

All of these problems have one cause: the ground is built differently from how it looks. It is not a sculpture but a grid of points, and each point can move in only one way, up or down. Once you know this, you can tell what a brush can fix, what a setting at creation time can fix, and what needs a mesh, a material or another tool. The lesson How a world is built: from large to small shows where the ground comes in the order of work on a world: right after the idea and the scale.

Further in the article

1. Heightmap: brightness is height
2. Grid step: how many meters between vertices
3. Height precision: 8 bits give a staircase, 16 bits a slope
4. The ground is cut into pieces: components and sections
5. Fewer vertices in the distance, and stitching the seams
6. Brushes: what they do to the numbers
7. Edit layers: the ground can be redone
8. Ground paint: the weight of every layer at every vertex
9. What a heightmap cannot do
10. How this works in Unreal
11. In other programs
12. Where it breaks
13. Connections: the same idea in other fields
14. Sources and further reading
15. Key points
16. Test yourself