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.

How to use

npm install meshline

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

Create an array of 3D coordinates

First, create the list of numbers that will define the 3D points for the line.

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

Create a MeshLine and assign the points

Once you have that, you can create a new MeshLineGeometry, and call .setPoints() passing the list of points.

const geometry = new MeshLineGeometry()
geometry.setPoints(points)

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

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

Cou can also provide a BufferGeometry by calling .setGeometry() instead.

geometry.setGeometry(myGeometry)

Create a MeshLineMaterial

MeshLineGeometry needs to be paired with MeshLineMaterial.

const material = new MeshLineMaterial(options)

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

MeshLineMaterial has several attributes to control the appereance of the MeshLine:

• 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.

Use MeshLine and MeshLineMaterial to create a THREE.Mesh

Finally, we create a mesh and add it to the scene:

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

You can optionally add raycast support with the following.

import { raycast } from 'meshline'

mesh.raycast = raycast

Declarative use

Meshline can be used declaritively. This is how it would look like in react-three-fiber. You can try it live here.

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

extend({ MeshLine, MeshLineMaterial })

function Line({ points, width, color }) {  
  return (
    <Canvas>
      <mesh raycast={raycast}>
        <meshLineGeometry points={points} />
        <meshLineMaterial          
          transparent
          depthTest={false}
          lineWidth={width}
          color={color}
          dashArray={0.05}
          dashRatio={0.95}
        />
      </mesh>
    </Canvas>
  )
}

Dynamic line widths can be set along each point using the widthCallback prop.

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

References

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