---
title: "Road view (top-down): API"
package: "@phaser-ae/road-view-topdown"
tier: Free
version: 3.0.0-2
released: 2026-10-14
updated: 2026-10-19
description: "Draws a scrolling top-down road or a static track from data, with forks, bridges, rivers, painted surfaces, markings, roadside scenery and day-to-night light."
url: https://phaser.io/packs/road-view-topdown/api
site: Phaser - https://phaser.io
---

# Road view (top-down): API

`@phaser-ae/road-view-topdown` — Draws a top-down road or track from data: cross-section spans, features and markings as world-anchored tiled sprites, with roadside scatter and day-night light.

## The pack

### `roadViewTopdown`

```ts
function roadViewTopdown(): Pack<{ roadViewTopdown: RoadViewTopdownApi }>
```

Install the top-down road view: draws scrolling roads and static top-down tracks from data.

## Helpers

### `mapping`

```ts
function mapping(axis: RoadAxis, scale: number, camera: RoadCamera, viewport: { width: number; height: number; x?: number; y?: number }, margin = 0): Mapping
```

The mapping for an axis. `up`: u right, v up the screen (a vertical scroller driving up); `down`: u right,
v down the screen (a static top-down map, v = y); `right`: v to the right, u down; `left`: v to the left, u down.

### `paintArt`

```ts
function paintArt(g: Paint, w: number, h: number, look: ArtLook, seed = 3): void
```

Paint a built-in roadside object into a `w` x `h` canvas (texels), seen from above.

### `paintSurface`

```ts
function paintSurface(g: Paint, size: number, look: SurfaceLook, seed = 7): void
```

Paint one tile of a surface texture, `size` texels square, that repeats seamlessly.

### `polygonSource`

```ts
function polygonSource(shapes: readonly SurfaceShape[], extras: { features?: readonly RoadFeature[]; markings?: readonly RoadMarking[] } = {}): RoadSource
```

A static source from polygons, painted in order (later shapes over earlier). Each row is the scanline
crossing of every shape, so a circuit drawn as a track polygon with kerb and run-off polygons becomes ground
the view can draw: the track-racer's static circuits, a car park, an arena floor.

### `sampleChunk`

```ts
function sampleChunk(source: RoadSource, chunk: number, rowHeight: number, chunkRows: number, has?: (key: string) => boolean): RowRun[]
```

Sample rows `chunk * chunkRows` .. `(chunk + 1) * chunkRows - 1` (row `r` covers `r * rowHeight` to
`(r + 1) * rowHeight` and is sampled at its middle) and merge identical neighbours into runs.

### `scatterCell`

```ts
function scatterCell(rule: SceneryRule, ruleIndex: number, seed: number, i: number, j: number, surfaceAt: (u: number, v: number) => string): SceneryItem | null
```

The scatter for one grid cell of one rule: a candidate at a hashed position inside the cell, kept only when
its footprint (plus clearance) lies wholly on the rule's surfaces. `surfaceAt` must be the same ground the
view draws, so a tree never stands on a road edge.

### `surfaceIn`

```ts
function surfaceIn(spans: readonly RoadSpan[], u: number, background = ""): string
```

The surface showing at `u` in a cross-section (the last span covering it), or `background`.

### `tileUv`

```ts
function tileUv(axis: RoadAxis, u0: number, u1: number, v0: number, v1: number, tile: number, drift = 0): { repeatX: number; repeatY: number; scrollX: number; scrollY: number }
```

Texture coordinates that keep a tiled texture fixed to the world, whichever run or sprite a patch of ground
lands in: adjacent sprites continue the pattern seamlessly and a sprite that moves never slides its texture.

## Functions

### `hash01`

```ts
function hash01(a: number, b: number, c: number, d = 0): number
```

A small integer hash (deterministic across platforms) mapped to 0..1.

### `hex`

```ts
function hex(r: number, g: number, b: number): string
```

`#rrggbb` from channels (clamped).

### `mix`

```ts
function mix(a: string, b: string, t: number): string
```

Linear blend of two colours, t = 0 gives `a`.

### `rgb`

```ts
function rgb(c: string): [number, number, number]
```

Parse `#rgb` / `#rrggbb` to [r, g, b]. Other strings return grey.

### `sameSpans`

```ts
function sameSpans(a: readonly RoadSpan[], b: readonly RoadSpan[]): boolean
```

True when two cross-sections are the same (same spans, same order).

### `shade`

```ts
function shade(c: string, k: number): string
```

Lighten (k > 0) or darken (k < 0) a colour by a fraction.

## Classes

### `RoadPlanner`

```ts
class RoadPlanner
```

Turns a camera into the frame's sprites. Rows are sampled once per chunk and cached until the source's
`revision` changes; chunks behind the view are evicted. Keys are anchored to the world (chunk, run, span;
scatter cell; feature id; dash index), so a sprite always shows the same piece of ground.

- `readonly axis: RoadAxis` — The direction of increasing `v` on screen. Default `up`.
- `readonly scale: number` — Screen units per world unit. Default 1.
- `readonly rowHeight: number` — The row height in world units along `v`. Default 2.
- `readonly chunkRows: number` — Rows per cached chunk. Default 32.
- `sampled: number` — Rows sampled since creation (for tests and the stats readout).
- `constructor(readonly o: PlannerOptions)`
- `invalidate(): void` — Drop every cached row and scatter cell (the source changed rows already drawn).
- `runs(chunk: number): RowRun[]` — The cached runs of one chunk.
- `surfaceAt(u: number, v: number): string` — The surface the view draws at a world point (sampled at the row's middle, like the ground itself).
- `plan(camera: RoadCamera, time = 0): DrawItem[]` — The sprites for one frame. `time` drives flowing textures (seconds).

## Constants

### `frac`

```ts
const frac = (n: number): number=> …
```

Positive fractional part, so a texture offset is always 0..1 whichever side of zero the world is.

## Types

### `ArtLook`

```ts
interface ArtLook
```

How a feature or scenery kind is drawn: a built-in painting or an atlas frame of the game's own.

- `paint?: ArtName` — A built-in painting.
- `frame?: number` — Or an atlas frame added by the game.
- `colour?: string` — Main colour for built-in paintings (canopy, roof, rock).
- `colour2?: string` — Second colour (trunk, walls, shadow).
- `tint?: string` — Multiplicative tint at draw time. Default white.

### `ArtName`

```ts
type ArtName = | "tree" | "bush" | "pine" | "snow-pine" | "rock" | "cactus" | "house" | "barn" | "boathouse" | "bridge-rail" | "post" | "sign" | "tuft" | "reeds" | "dune" | "buoy" | "lamp"
```

Built-in art the view can paint for scenery and features.

### `DrawItem`

```ts
interface DrawItem
```

One sprite the view wants this frame: pure data, produced by `planFrame`.

- `key: string` — Stable key (same object, same key, every frame).
- `look: string` — What to draw: `surface:<id>`, `art:<kind>`, or `solid`.
- `x: number` — Screen centre x.
- `y: number` — Screen centre y.
- `w: number` — Screen width.
- `h: number` — Screen height.
- `rot: number` — Rotation, radians.
- `repeatX: number` — Texture repeats across the quad (1 = once).
- `repeatY: number` — Texture repeats down the quad.
- `scrollX: number` — Texture offset in tile fractions.
- `scrollY: number` — Texture offset in tile fractions.
- `tint: string` — Tint (before the light).
- `z: number` — Draw order.

### `Mapping`

```ts
interface Mapping
```

World-to-screen mapping for one frame.

- `toScreen(u: number, v: number): { x: number; y: number }` — Screen position of a world point.
- `toWorld(x: number, y: number): { u: number; v: number }` — World point under a screen position.
- `rect(u0: number, u1: number, v0: number, v1: number): { x: number; y: number; w: number; h: number }` — Screen rectangle (centre and size) of a world box.
- `readonly bounds: { u0: number; u1: number; v0: number; v1: number }` — The world box the viewport shows.

### `Paint`

```ts
type Paint = Pick<OffscreenCanvasRenderingContext2D, "fillStyle" | "fillRect" | "beginPath" | "arc" | "ellipse" | "fill" | "moveTo" | "lineTo" | "closePath" | "strokeStyle" | "lineWidth" | "stroke" | "globalAlpha">
```

The drawing calls the paintings use (an OffscreenCanvas or a canvas 2D context).

### `PlannerOptions`

```ts
interface PlannerOptions
```

The planner's options (the view's options minus the kernel-only ones).

- `source: RoadSource` — The road to draw.
- `surfaces: Readonly<Record<string, SurfaceLook>>` — Surface looks by id. Unknown ids draw magenta so a missing entry is obvious.
- `background?: string` — The surface id under everything, where no span covers. Default none (transparent).
- `axis?: RoadAxis` — Direction of increasing `v` on screen. Default `up`.
- `scale?: number` — Screen units per world unit. Default 1.
- `viewport: { width: number; height: number; x?: number; y?: number }` — The screen area to cover: width and height in screen units, and optionally its top-left `x` and `y`.
- `rowHeight?: number` — The row height in world units along `v`. Default 2; must be above 0.
- `chunkRows?: number` — Rows per cached chunk. Default 32; must be a whole number of 1 or more.
- `scenery?: readonly SceneryRule[]` — Roadside scatter rules, applied in order (an earlier rule's object blocks a later one's cell).
- `seed?: number` — Scatter seed. Default 1.
- `z?: number` — Base draw order; ground at base, markings +1, features +2, scenery +4. Default -100.
- `margin?: number` — Extra margin drawn beyond the viewport, in world units. Default 8.

### `RoadAxis`

```ts
type RoadAxis = "up" | "down" | "left" | "right"
```

Which way the road's `v` axis runs on screen.

### `RoadCamera`

```ts
interface RoadCamera
```

Where the camera looks: the world point (`u`, `v`) drawn at screen (`x`, `y`).

- `u: number` — Across, world units.
- `v: number` — Along, world units.
- `x?: number` — Screen x of that point. Default: viewport centre.
- `y?: number` — Screen y of that point. Default: viewport centre.

### `RoadFeature`

```ts
interface RoadFeature
```

A placed piece of the road's own furniture: a boathouse, a bridge rail, a sign, a gantry.

- `id: string | number` — Stable id: the same feature keeps the same sprite while it is on screen.
- `kind: string` — A key in the view's `art` table (or one of the built-in art names).
- `u: number` — Centre across, world units.
- `v: number` — Centre along, world units.
- `width: number` — Size across, world units.
- `length: number` — Size along, world units.
- `rot?: number` — Rotation in radians, clockwise on screen. Default 0.
- `tint?: string` — Multiplicative tint. Default white.
- `z?: number` — Draw order relative to the view's base z. Default 2 (over the ground, under the scenery's tall items).

### `RoadMarking`

```ts
interface RoadMarking
```

A painted line along the road: a lane divider, an edge line, a dashed centre line.

- `id: string | number` — Stable id. Dashes are keyed by this id plus their world dash index, so they never swap sprites.
- `u: number` — Centre of the line across, world units.
- `from: number` — Start along, world units.
- `to: number` — End along, world units (> from).
- `width?: number` — Line width, world units. Default 1.
- `dash?: number` — Dash length; omitted or 0 draws a solid line.
- `gap?: number` — Gap between dashes. Default equal to `dash`.
- `colour?: string` — Line colour. Default white.

### `RoadSource`

```ts
interface RoadSource
```

What the view draws from. Any object with `spansAt` is a source: a scrolling road generated as it is driven
(road-combat's course), a static circuit rasterised from polygons (`polygonSource`), or a hand-written function.

- `spansAt(v: number): readonly RoadSpan[]` — The cross-section at `v`: spans in paint order. Must be a pure function of `v` for a given `revision`.
- `featuresIn?(v0: number, v1: number): readonly RoadFeature[]` — Furniture whose extent overlaps `v0`..`v1` (v0 < v1). Optional.
- `markingsIn?(v0: number, v1: number): readonly RoadMarking[]` — Markings overlapping `v0`..`v1`. Optional.
- `lookAt?(v: number): string | null` — The look (palette, region) at `v`, optional. When the view's `surfaces` has a key `<surface>@<look>`, it is used for that surface there; otherwise the plain `<surface>` key. One road can then change colours by region.
- `readonly revision?: number` — Bump when spans that were already sampled change (a road generated further ahead does not count: rows the view has not reached are sampled fresh). The view drops its cached rows when this changes.

### `RoadSpan`

```ts
interface RoadSpan
```

One stretch of surface across the road at one position along it. `from` < `to`, world units across.

- `from: number` — Left edge in the across axis `u`, world units.
- `to: number` — Right edge in the across axis `u`, world units.
- `surface: string` — A surface id, looked up in the view's `surfaces` table.

### `RoadView`

```ts
interface RoadView
```

A road being drawn. Call `draw(camera)` once per fixed step, from the game's step.

- `draw(camera: RoadCamera, o?: { snap?: boolean; time?: number }): void` — Plan and draw the frame. `snap` cuts interpolation (a respawn, a camera jump); `time` drives flowing water.
- `setLight(amount: number, colour?: string): void` — Day and night: blend every road sprite toward `colour` by `amount` (0 = day, 1 = full night tint).
- `invalidate(): void` — Forget cached rows (the source changed ground already drawn).
- `toScreen(u: number, v: number): { x: number; y: number }` — Screen position of a world point for the last drawn camera (to place the game's own sprites).
- `toWorld(x: number, y: number): { u: number; v: number }` — World point under a screen position for the last drawn camera.
- `readonly bounds: { u0: number; u1: number; v0: number; v1: number }` — The world box the last frame covered.
- `readonly stats: { shown: number; pooled: number; rowsSampled: number }` — Sprites shown last frame and the pool size.
- `readonly planner: RoadPlanner` — The planner (pure): for tests and for games that want the plan without the sprites.
- `dispose(): void` — Hide and release every sprite.

### `RoadViewOptions`

```ts
interface RoadViewOptions
```

Options for `create()`.

- `source: RoadSource` — The road to draw.
- `surfaces: Readonly<Record<string, SurfaceLook>>` — Surface looks by id. Unknown ids draw magenta so a missing entry is obvious.
- `background?: string` — The surface under everything, where no span covers. Default: none (transparent).
- `axis?: RoadAxis` — Direction of increasing `v` on screen. `up` for a vertical scroller driving up the screen. Default `up`.
- `scale?: number` — Screen units per world unit. Default 1.
- `viewport: { width: number; height: number; x?: number; y?: number }` — Viewport in screen units (the area to cover).
- `rowHeight?: number` — Rows sampled per world unit along `v`: the row height in world units. Default 2.
- `chunkRows?: number` — Rows per cached chunk. Default 32.
- `scenery?: readonly SceneryRule[]` — Roadside scatter rules, applied in order (an earlier rule's object blocks a later one's cell).
- `art?: Readonly<Record<string, ArtLook>>` — Art for features (and named overrides of built-ins), by kind.
- `seed?: number` — Scatter seed. Default 1.
- `layer?: string` — Render layer. Default `hud` (the world-screen layer games draw in).
- `z?: number` — Base draw order; ground at base, markings +1, features +2, scenery +4. Default -100.
- `margin?: number` — Extra margin drawn beyond the viewport, world units. Default 8.
- `resolution?: number` — Texels painted per world unit for the built-in textures and art. Default 1 (one texel per unit: crisp pixel art when units are pixels). A road in metres wants about 5.

### `RoadViewTopdownApi`

```ts
interface RoadViewTopdownApi
```

The composed `game.roadViewTopdown` API.

- `create(options: RoadViewOptions): RoadView` — Draw a road from a source: retained, world-anchored sprites (see the pack page).
- `polygonSource: typeof polygonSource` — A static source from filled polygons (a top-down circuit, an arena floor).
- `RoadPlanner: typeof RoadPlanner` — The pure planner, for headless use.
- `mapping: typeof mapping` — World-to-screen mapping for an axis, scale and camera.
- `sampleChunk: typeof sampleChunk` — Sample one chunk of rows into runs of identical cross-sections.
- `scatterCell: typeof scatterCell` — The deterministic scatter for one grid cell of a scenery rule.
- `surfaceIn: typeof surfaceIn` — The surface showing at a point of a cross-section.
- `tileUv: typeof tileUv` — World-anchored texture repeat and scroll for a rectangle of ground.
- `paintSurface: typeof paintSurface` — Paint a tiling surface texture into a canvas.
- `paintArt: typeof paintArt` — Paint a built-in roadside object into a canvas.
- `mix: typeof mix` — Blend two colours.
- `shade: typeof shade` — Lighten or darken a colour.

### `RowRun`

```ts
interface RowRun
```

A merged run of identical rows inside one chunk.

- `v0: number` — First along-position covered.
- `v1: number` — Last along-position covered (exclusive).
- `spans: readonly RoadSpan[]` — The cross-section shared by every row of the run.

### `SceneryItem`

```ts
interface SceneryItem
```

One roadside object chosen by the scatter.

- `key: string` — Stable key: rule, cell across, cell along.
- `rule: number` — Index of the rule.
- `kind: number` — Index of the kind within the rule.
- `u: number` — Centre across.
- `v: number` — Centre along.
- `width: number` — Size across.
- `length: number` — Size along.

### `SceneryKind`

```ts
interface SceneryKind
```

One kind of roadside object for the scatter.

- `art: ArtLook` — Built-in art or a frame.
- `width: number` — Size across, world units.
- `length: number` — Size along, world units.
- `weight?: number` — Relative chance among the rule's kinds. Default 1.

### `SceneryRule`

```ts
interface SceneryRule
```

Roadside scatter: objects placed deterministically on a world grid (so they never move or pop as the road
scrolls), kept only where their whole footprint, plus `clearance`, lies on one of the `on` surfaces.

- `on: string | readonly string[]` — Surfaces the objects may stand on.
- `kinds: readonly SceneryKind[]` — Kinds to choose from.
- `spacing?: number` — Grid cell size in world units (one candidate per cell). Default 24.
- `chance?: number` — Chance that a cell holds an object, 0..1. Default 0.6.
- `clearance?: number` — Extra margin that must also be on an allowed surface, world units. Default 2.
- `z?: number` — Draw order relative to the base z. Default 4.

### `SurfaceLook`

```ts
interface SurfaceLook
```

How one surface looks.

- `colour: string` — Base colour (CSS).
- `pattern?: SurfacePattern` — Painted pattern. Default `flat`.
- `detail?: readonly string[]` — Detail colours for the pattern (speckles, ripples, blades). Default: shades of the base colour.
- `density?: number` — Detail density 0..1. Default 0.35.
- `tile?: number` — World units per texture tile. Default 32.
- `flow?: number` — Texture drift along the road, world units per second (a river's current). Default 0.
- `frame?: number` — Use this atlas frame (already added by the game) instead of painting one.

### `SurfacePattern`

```ts
type SurfacePattern = | "flat" | "grain" | "speckle" | "grass" | "water" | "ice" | "snow" | "sand" | "gravel" | "planks" | "stripes" | "checker"
```

Built-in surface patterns the view can paint without any art from the game.

### `SurfaceShape`

```ts
interface SurfaceShape
```

A filled polygon for `polygonSource`.

- `surface: string` — Surface id.
- `points: ReadonlyArray<{ u: number; v: number }>` — Outline, at least three points, in (u, v) world units. Any winding; self-crossings fill by even-odd.

---

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