---
title: "Vector Terrain"
package: "@phaser-ae/vector-terrain"
tier: Free
version: 3.0.0-3
released: 2026-10-14
updated: 2026-10-20
description: "Seeded line landscapes for 2D games, generated by midpoint displacement, sampled for a height at any x, flattened into landing pads and blown into craters."
url: https://phaser.io/packs/vector-terrain
site: Phaser - https://phaser.io
---

# Vector Terrain

Line landscapes for 2D games: one seeded polyline you can sample for a height anywhere, flatten into landing pads and
blow craters into, without it ever folding over itself.

## What it does

`generateTerrain` builds a landscape by midpoint displacement: it repeatedly splits each segment and pushes the new
middle up or down by a shrinking amount. One number, the roughness, takes it from rolling hills to a mountain range.
Both ends sit at the base height, and with a seed, or the game's own random source, the same landscape comes back
every time.

The landscape is single-valued in x by construction, and everything else depends on that. Because no two vertices
share an x, `heightAtX` finds the one segment that spans any x and returns the ground height there with a binary
search, cheaply every frame. `climbableX` tests whether the rise between two positions is within a slope.
`flattenTerrain` lays an exact pad or plateau and returns where it is. `craterHeightfield` carves a bowl.

A general polyline will not stand that treatment: carve two overlapping craters into an arbitrary outline and the line
folds back on itself, after which "the height at x" has no answer. Here a crater only ever pushes vertices down,
clamped to a floor, and every function keeps the vertices sorted, so the field stays single-valued however many
shells land on it.

## Features

- **Midpoint displacement** — `generateTerrain` with a width, a base height, an amplitude, a roughness from 0 to 1,
  and clamps on how high and low the ground may go.
- **Spacing or passes** — ask for a widest vertex gap with `spacing`, or a number of `iterations`, up to 16 passes.
- **Seeded** — a `seed` or an `rng`; through `game.vecTerrain` it draws from the game's random source by default, so
  terrain replays with the game's seed.
- **Height anywhere** — `heightAtX` by binary search, `Infinity` off either end.
- **Landing pads** — `flattenTerrain` makes the ground flat between two x positions, at a height you choose or the
  middle's, and returns the pad.
- **Slope tests** — `climbableX` checks a rise against a maximum slope; downhill always passes.
- **Craters** — `craterHeightfield` lowers the ground inside a circle to a bowl, never below a floor, optionally
  refining the ground under it first.
- **Detail on demand** — `refineTerrain` adds vertices in a span without changing its shape, so a crater can bite
  into ground generated coarsely.

## Good for

- **Lander games** — a jagged landscape with flat pads, in the style of Lunar Lander.
- **Artillery games** — ground that craters under every shell and stays a clean line.
- **Side-scrolling shooters** — the ground and, with a second field, the ceiling of a cave, in the style of Scramble.
- **Moon-buggy and driving games** — a surface to sample under the wheels, with slope checks for climbing, in the
  style of Moon Patrol.

## Make it yours

The options shape the land: `width` and `baseY`, the first displacement `amplitude`, the `roughness` that decides how
much survives each pass, `iterations` or a `spacing`, `minY` and `maxY` clamps, and a `seed` or an `rng`. A cave is two
landscapes from two calls, a ceiling with a small `baseY` and a floor with a large one; a vertical shaft is a landscape
generated across the height and mapped with x and y swapped, then sampled with `heightAtX(shaft, y)`.

Two very different games from the same calls: a lunar landing on a 2,400-unit landscape with a roughness of 0.55 and
two flattened pads at different heights; and an artillery duel on gentle rolling hills where every shell calls
`craterHeightfield` with a refinement step, so the ground under the tanks wears away shot by shot.

## A quick look

A lunar landscape with two pads, a landing check, and a crater handed back to the drawn line:

```ts
const T = game.vecTerrain;
const ground = T.generateTerrain({ width: 2400, baseY: 520, amplitude: 180, roughness: 0.55, spacing: 12, minY: 260, maxY: 700 });
const pads = [T.flattenTerrain(ground, 400, 460), T.flattenTerrain(ground, 1500, 1540, 610)];
const line = game.vector.shape(ground, { closed: false, color: '#c8d0ff' });
if (craft.y + 10 >= T.heightAtX(ground, craft.x)) { /* landed on a pad, or crashed on the rocks */ }
T.craterHeightfield(ground, shell.x, shell.y, 24, 700, { step: 4 });
line.setPoints(ground, false);
```

## Works with

- `vector-2d` — draws the line, and takes the changed points after a crater.
- `vector-hit` — collision against the line, through its wall segments.
- `physics-box2d` — makes the line solid ground for bodies, as a chain.
- `thrust-craft` — caves of several chains with graded contact, built on these heights.
- `lander-missions` — landing-site rules and scoring.
- `excavation`, `procgen` and `terrain-3d` — terrain dug cell by cell, seeded noise for other shapes, and the 3D
  counterpart.

## Good to know

- One line, with no overhangs and no caves in a single field: a tunnel needs two fields or a different representation.
- Without a refinement step, a crater narrower than the vertex spacing only moves the vertices inside it, so it carves
  a notch or nothing.
- A crater's floor bounds how deep the crater digs, not the terrain: ground already below it is left alone.
- `climbableX` is a two-point slope test, not a walk, so a vehicle that should stop partway up a hill has to step it
  itself.
- The functions change the array in place, so anything built from it, a drawn shape or a physics chain, must be given
  the new points.

---

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