---
title: "Lines in a 3D world"
package: "@phaser-ae/lines-3d"
tier: Free
version: 3.0.0-4
released: 2026-10-14
updated: 2026-10-20
description: "Polylines in a 3D scene, such as a route, a wire, an axis or a debug ray, drawn at a constant width in screen pixels however far away they are."
url: https://phaser.io/packs/lines-3d
site: Phaser - https://phaser.io
---

# Lines in a 3D world

Polylines as objects: a route, a wire, an axis, a debug ray, drawn at a constant width in screen pixels. The test for
whether you want this pack is whether the thing should get thinner as it recedes. A rope should; a route should not.

## What it does

A line is an object with a `points` array that your game owns. Mutate it in place or assign a new one, as points or as
a flat run of numbers, and it is read and re-uploaded each frame, with no commit step. A path from a pathfinder, a
raycast from a weapon or the corners of a selection become visible by assigning them.

Each segment is expanded on the GPU into a quad facing the camera, its half-width scaled by its own distance to the
eye, which is what holds the line at a constant pixel width near and far. A segment pointing straight at the camera
falls back to the camera's right rather than vanishing. Lines are depth-tested, so a route behind a hill is hidden by
the hill, and `xray` draws one over everything. Every segment of every line shares one buffer and goes out in at most
two draws.

## Features

- **Lines as objects** — `add` returns a line whose points, colour, width, alpha, closed flag, visibility and x-ray
  are all live.
- **Constant pixel width** — legible at any distance, set per line or as a default.
- **Shortcuts** — `segment` for a straight run between two points, and `box` for the twelve edges of an
  axis-aligned box.
- **Depth-tested or x-ray** — hidden by solids in front of it, or drawn through them for debugging and selection.
- **Cheap** — at most two draws for every line in the scene, with `drawn` reporting the segments.

## Good for

- **Strategy and tactics games** — showing a unit's planned route or a patrol path over the terrain.
- **Debugging** — raycasts, navigation paths and bounding boxes made visible while you work.
- **Editors and tools** — world axes, gizmos and the edges of a selection.
- **Puzzle and wiring games** — wires and connections between objects that read clearly from any angle.
- **Tethers and links** — a line from a grappling point to the player, or between linked objects.

## Make it yours

Each line takes its points, colour, pixel width, alpha, whether it closes into a loop, whether it is visible and
whether it draws as an x-ray. The pack's options set the default width (2 pixels), the default colour and whether the
pass starts on. Two different uses: a strategy game drawing each selected unit's route in its team colour, a little
above the ground and hidden behind hills, rewritten whenever the path changes; and a debug view that draws every
raycast as a red x-ray segment and every collider's bounds as a yellow box, visible through walls.

## A quick look

A route rewritten every step, a debug ray drawn through solids and a bounding box:

```ts
const route = game.lines3d.add({ color: '#5cf0ff', width: 2.5 });
route.points = path.map(p => ({ x: p.x, y: p.y + 0.5, z: p.z }));
game.lines3d.segment({ x: 0, y: 0, z: 0 }, hit, { color: '#ff4040', xray: true });
game.lines3d.box(bounds.min, bounds.max, { color: '#ffd166' });
```

## Works with

- `render-3d` — draws the lines into the 3D scene and supplies the depth they test against.
- `nav-mesh` and `path-3d` — routes and paths to show as lines.
- `beams-3d` — for a visible shaft of light rather than a line.
- `trails-3d` — for a trail behind a moving object.

## Good to know

- No dashes, caps or joins: a corner is two quads meeting, which shows a notch at very wide widths.
- One colour and one width per line; use two lines for a change of either.
- Lines do not write depth, so where two lines cross they resolve by the order they were packed, not by depth.
- Lines cast no shadows and cannot be picked; headless, they are held but not drawn.

---

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