meshline

MeshLine

A mesh replacement for THREE.Line. Instead of using GL_LINE, it uses a strip of billboarded triangles. This is a fork of spite/THREE.MeshLine, previously maintained by studio Utsuboco.

How to use

npm install meshline

import * as THREE from 'three'
import { MeshLineGeometry, MeshLineMaterial, raycast } from 'meshline'

const geometry = new MeshLineGeometry()
geometry.setPoints([...])
const material = new MeshLineMaterial({ ... })
const mesh = new THREE.Mesh(geometry, material)
mesh.raycast = raycast
scene.add(mesh)

Assign points

Create a MeshLineGeometry and pass a list of points into .setPoints(). Expected inputs are:

• Float32Array
• THREE.BufferGeometry
• Array<THREE.Vector3 | THREE.Vector2 | [number, number, number] | [number, number] | number>

const geometry = new MeshLineGeometry()

const points = []
for (let j = 0; j < Math.PI; j += (2 * Math.PI) / 100)
  points.push(Math.cos(j), Math.sin(j), 0)

geometry.setPoints(points)

Note: .setPoints accepts a second parameter, which is a function to define a variable width for each point along the line. By default that value is 1, making the line width 1 * lineWidth.

// p is a decimal percentage of the number of points
// ie. point 200 of 250 points, p = 0.8
geometry.setPoints(points, (p) => 2) // makes width 2 * lineWidth
geometry.setPoints(points, (p) => 1 - p) // makes width taper
geometry.setPoints(points, (p) => 2 + Math.sin(50 * p)) // makes width sinusoidal

Create a material

const material = new MeshLineMaterial(options)

By default it's a white material of width 1 unit.

MeshLineMaterial has several attributes to control the appereance:

• map - a THREE.Texture to paint along the line (requires useMap set to true)
• useMap - tells the material to use map (0 - solid color, 1 use texture)
• alphaMap - a THREE.Texture to use as alpha along the line (requires useAlphaMap set to true)
• useAlphaMap - tells the material to use alphaMap (0 - no alpha, 1 modulate alpha)
• repeat - THREE.Vector2 to define the texture tiling (applies to map and alphaMap)
• color - THREE.Color to paint the line width, or tint the texture with
• opacity - alpha value from 0 to 1 (requires transparent set to true)
• alphaTest - cutoff value from 0 to 1
• dashArray - the length and space between dashes. (0 - no dash)
• dashOffset - defines the location where the dash will begin. Ideal to animate the line.
• dashRatio - defines the ratio between that is visible or not (0 - more visible, 1 - more invisible).
• resolution - THREE.Vector2 specifying the canvas size (REQUIRED)
• sizeAttenuation - constant lineWidth regardless of distance (1 is 1px on screen) (0 - attenuate, 1 - don't)
• lineWidth - float defining width (if sizeAttenuation is true, it's world units; else is screen pixels)

If you're rendering transparent lines or using a texture with alpha map, you should set depthTest to false, transparent to true and blending to an appropriate blending mode, or use alphaTest.

Form a mesh

const mesh = new THREE.Mesh(geometry, material)
scene.add(mesh)

Raycasting

Raycast can be optionally added by overwriting mesh.raycast with the one that meshline provides.

import { raycast } from 'meshline'

mesh.raycast = raycast

Declarative use

Meshline can be used declaritively in react-three-fiber. MeshLineGeometry has a convenience setter/getter for .setPoints(), points.

import { Canvas, extend } from '@react-three/fiber'
import { MeshLineGeometry, MeshLineMaterial, raycast } from 'meshline'

extend({ MeshLineGeometry, MeshLineMaterial })

function App() {
  return (
    <Canvas>
      <mesh raycast={raycast} onPointerOver={console.log}>
        <meshLineGeometry points={[0, 0, 0, 1, 0, 0]} />
        <meshLineMaterial lineWidth={1} color="hotpink" />
      </mesh>
    </Canvas>
  )
}

Variable line widths

Variable line widths can be set for each point using the widthCallback prop.

<meshLineGeometry points={points} widthCallback={(p) => p * Math.random()} />

Types

Add these declarations to your entry point.

import { Object3DNode, MaterialNode } from '@react-three/fiber'

declare module '@react-three/fiber' {
  interface ThreeElements {
    meshLineGeometry: Object3DNode<MeshLineGeometry, typeof MeshLineGeometry>
    meshLineMaterial: MaterialNode<MeshLineMaterial, typeof MeshLineMaterial>
  }
}

References

• Drawing lines is hard
• WebGL rendering of solid trails
• Drawing Antialiased Lines with OpenGL