--- title: "Vector Terrain: API" 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/api site: Phaser - https://phaser.io --- # Vector Terrain: API `@phaser-ae/vector-terrain` — Line heightfields: seeded midpoint-displacement landscapes you can sample at any x, flatten into landing pads and blow craters into. ## The pack ### `vectorTerrain` ```ts function vectorTerrain(): Pack<{ vecTerrain: VecTerrainApi }> ``` The `vector-terrain` pack. Pure maths, so it needs no backend and runs headless. ## Helpers ### `climbableX` ```ts function climbableX(terrain: readonly Vec2[], fromX: number, toX: number, maxClimbSlope: number): number ``` Slope-limited horizontal step along a heightfield. Returns the ALLOWED x: `toX` if the step's uphill slope is within `maxClimbSlope` (rise/run — ~1 is 45°), otherwise `fromX` (refused). Downhill is always allowed. ### `craterHeightfield` ```ts function craterHeightfield(polyline: Vec2[], cx: number, cy: number, radius: number, floorY: number, opts: CraterOptions = {}): void ``` Blow a crater into a heightfield polyline, in place — destructible terrain. Lowers the surface within `radius` of (cx, cy) following a circular bowl, ONLY ever pushing the ground down and clamping to `floorY`, so the surface stays single-valued and `heightAtX` stays valid. With `step`, vertices are added under the crater first so it keeps its shape however coarse the terrain is. ### `flattenTerrain` ```ts function flattenTerrain(polyline: Vec2[], fromX: number, toX: number, y?: number): { x0: number; x1: number; y: number } ``` Flatten the ground between `fromX` and `toX` to height `y`, IN PLACE: a landing pad, a plateau, a runway, a firing position. Vertices are added at both edges so the flat runs exactly from `fromX` to `toX`, and the vertices between are set to `y`, raised or lowered, so the field stays single-valued. `y` defaults to the ground height at the middle of the span. Returns the pad as `{ x0, x1, y }`, clamped to the polyline's span. ### `generateTerrain` ```ts function generateTerrain(opts: HeightfieldOptions): Vec2[] ``` Midpoint-displacement terrain as a polyline, sorted left-to-right and single-valued in x, ready for `heightAtX`, `flattenTerrain`, `craterHeightfield`, `game.vector.shape(points, { closed: false })` and `vector-hit`'s `polylineSegments`. Deterministic: the same `seed` (or `rng` stream) gives the same ground. Generate once per level; never per frame. Throws on a width that is not positive or a pass count past {@link TERRAIN_MAX_ITERATIONS}. ### `heightAtX` ```ts function heightAtX(polyline: readonly Vec2[], x: number): number ``` Sample the y of a terrain polyline at world x, linearly interpolating between the two vertices spanning x. Points must be sorted by x ascending (every function here keeps them so). A binary search, so it is cheap to call per body per frame. Returns Infinity if x is outside the polyline (treat as: no ground here). ### `refineTerrain` ```ts function refineTerrain(polyline: Vec2[], fromX: number, toX: number, maxSpacing: number): number ``` Add vertices to a terrain polyline, IN PLACE, so no segment between `fromX` and `toX` is longer than `maxSpacing` world units. The shape does not change (each new vertex sits on the old line); what changes is how finely a crater or a pad can then bend it. Clamped to the polyline's own span. Returns the number of vertices added. Throws on a `maxSpacing` that is not positive. ### `TERRAIN_MAX_ITERATIONS` ```ts const TERRAIN_MAX_ITERATIONS: 16 ``` The most subdivision passes {@link generateTerrain} runs: 2^16 + 1 vertices, a bound on memory and time. ## Types ### `CraterOptions` ```ts interface CraterOptions ``` Options for {@link craterHeightfield}. - `step?: number` — Refine the ground under the crater first, so no segment within it is longer than this, world units. A crater narrower than the terrain's own vertex spacing then carves a real bowl instead of a notch. Default unset: only the vertices already there move. ### `HeightfieldOptions` ```ts interface HeightfieldOptions ``` Options for `generateTerrain`: the span, ground level, roughness, resolution, clamps and seed of a midpoint-displacement heightfield. - `width: number` — Span on x, world units: the terrain runs 0..width. Must be positive. - `baseY: number` — Average ground height (screen y; larger = lower on screen). Both ends sit exactly here. - `amplitude?: number` — Initial vertical displacement, world units. Default `baseY * 0.4`. - `roughness?: number` — 0..1: how much amplitude survives each subdivision. Default 0.5; higher is more jagged. - `iterations?: number` — Subdivision passes: `2^iterations + 1` points. Default 6. Ignored when `spacing` is set. - `spacing?: number` — The widest gap between neighbouring vertices, world units: the fewest passes whose spacing is at most this (`width / 2^n <= spacing`), so the resolution follows the world rather than a pass count. Generate it finer than the smallest crater or pad. Default unset, which uses `iterations`. - `minY?: number` — Clamp ceiling: the highest the ground may rise (smallest y). Default 0. - `maxY?: number` — Clamp floor: the lowest the ground may sink (largest y). Default `baseY * 2`. - `seed?: number` — Seed for the displacement: the same seed and options give the same landscape. Default 1. Ignored when `rng` is given. - `rng?: () => number` — A random source returning [0, 1), such as `() => game.rng.next()`. Default a stream seeded by `seed`. ### `Vec2` ```ts interface Vec2 ``` A 2D point or vector. Plain data, so anything can produce one. - `x: number` — Horizontal coordinate, in world units, increasing to the right. - `y: number` — Vertical coordinate, in world units; the 2D world is Y-down, so larger is lower on screen. ### `VecPt` ```ts type VecPt = Vec2 ``` A point on a path — the same shape, named for what it is used as. ### `VecTerrainApi` ```ts type VecTerrainApi = typeof kit ``` `game.vecTerrain` — every function this pack carries, as one namespace. Its `generateTerrain` draws from `game.rng` when the options give neither `seed` nor `rng`, so a game's terrain replays with the game's seed. --- ## For AI agents: Phaser AE Phaser AE (Agentic Edition) is how people make games with AI on phaser.io. 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