154 lines
5.4 KiB
Markdown
154 lines
5.4 KiB
Markdown
# MeshLine
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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](https://github.com/spite/THREE.MeshLine), previously maintained by studio [Utsuboco](https://github.com/utsuboco).
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<p align="center">
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<img width="32%" src="screenshots/demo.jpg" alt=""/>
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<img width="32%" src="screenshots/graph.jpg" alt=""/>
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<img width="32%" src="screenshots/spinner.jpg" alt=""/>
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<img width="32%" src="screenshots/svg.jpg" alt=""/>
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<img width="32%" src="screenshots/shape.jpg" alt=""/>
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<img width="32%" src="screenshots/birds.jpg" alt=""/>
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</p>
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### How to use
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```
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npm install meshline
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```
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```jsx
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import * as THREE from 'three'
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import { MeshLineGeometry, MeshLineMaterial, raycast } from 'meshline'
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const geometry = new MeshLineGeometry()
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geometry.setPoints([...])
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const material = new MeshLineMaterial({ ... })
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const mesh = new THREE.Mesh(geometry, material)
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mesh.raycast = raycast
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scene.add(mesh)
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```
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#### Assign points
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Create a `MeshLineGeometry` and pass a list of points into `.setPoints()`. Expected inputs are:
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- `Float32Array`
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- `THREE.BufferGeometry`
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- `Array<THREE.Vector3 | THREE.Vector2 | [number, number, number] | [number, number] | number>`
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```jsx
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const geometry = new MeshLineGeometry()
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const points = []
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for (let j = 0; j < Math.PI; j += (2 * Math.PI) / 100)
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points.push(Math.cos(j), Math.sin(j), 0)
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geometry.setPoints(points)
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```
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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.
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```jsx
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// p is a decimal percentage of the number of points
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// ie. point 200 of 250 points, p = 0.8
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geometry.setPoints(points, (p) => 2) // makes width 2 * lineWidth
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geometry.setPoints(points, (p) => 1 - p) // makes width taper
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geometry.setPoints(points, (p) => 2 + Math.sin(50 * p)) // makes width sinusoidal
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```
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#### Create a material
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```jsx
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const material = new MeshLineMaterial(options)
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```
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By default it's a white material of width 1 unit.
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`MeshLineMaterial` has several attributes to control the appereance:
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- `map` - a `THREE.Texture` to paint along the line (requires `useMap` set to true)
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- `useMap` - tells the material to use `map` (0 - solid color, 1 use texture)
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- `alphaMap` - a `THREE.Texture` to use as alpha along the line (requires `useAlphaMap` set to true)
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- `useAlphaMap` - tells the material to use `alphaMap` (0 - no alpha, 1 modulate alpha)
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- `repeat` - THREE.Vector2 to define the texture tiling (applies to map and alphaMap)
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- `color` - `THREE.Color` to paint the line width, or tint the texture with
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- `opacity` - alpha value from 0 to 1 (requires `transparent` set to `true`)
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- `alphaTest` - cutoff value from 0 to 1
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- `dashArray` - the length and space between dashes. (0 - no dash)
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- `dashOffset` - defines the location where the dash will begin. Ideal to animate the line.
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- `dashRatio` - defines the ratio between that is visible or not (0 - more visible, 1 - more invisible).
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- `resolution` - `THREE.Vector2` specifying the canvas size (REQUIRED)
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- `sizeAttenuation` - constant lineWidth regardless of distance (1 is 1px on screen) (0 - attenuate, 1 - don't)
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- `lineWidth` - float defining width (if `sizeAttenuation` is true, it's world units; else is screen pixels)
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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`.
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#### Form a mesh
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```jsx
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const mesh = new THREE.Mesh(geometry, material)
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scene.add(mesh)
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```
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### Raycasting
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Raycast can be optionally added by overwriting `mesh.raycast` with the one that meshline provides.
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```jsx
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import { raycast } from 'meshline'
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mesh.raycast = raycast
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```
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### Declarative use
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Meshline can be used declaritively in [react-three-fiber](https://github.com/pmndrs/react-three-fiber). `MeshLineGeometry` has a convenience setter/getter for `.setPoints()`, `points`.
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```jsx
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import { Canvas, extend } from '@react-three/fiber'
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import { MeshLineGeometry, MeshLineMaterial, raycast } from 'meshline'
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extend({ MeshLineGeometry, MeshLineMaterial })
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function App() {
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return (
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<Canvas>
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<mesh raycast={raycast} onPointerOver={console.log}>
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<meshLineGeometry points={[0, 0, 0, 1, 0, 0]} />
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<meshLineMaterial lineWidth={1} color="hotpink" />
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</mesh>
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</Canvas>
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)
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}
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```
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#### Variable line widths
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Variable line widths can be set for each point using the `widthCallback` prop.
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```jsx
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<meshLineGeometry points={points} widthCallback={(p) => p * Math.random()} />
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```
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#### Types
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Add these declarations to your entry point.
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```tsx
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import { Object3DNode, MaterialNode } from '@react-three/fiber'
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declare module '@react-three/fiber' {
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interface ThreeElements {
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meshLineGeometry: Object3DNode<MeshLineGeometry, typeof MeshLineGeometry>
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meshLineMaterial: MaterialNode<MeshLineMaterial, typeof MeshLineMaterial>
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}
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}
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```
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### References
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- [Drawing lines is hard](http://mattdesl.svbtle.com/drawing-lines-is-hard)
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- [WebGL rendering of solid trails](http://codeflow.org/entries/2012/aug/05/webgl-rendering-of-solid-trails/)
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- [Drawing Antialiased Lines with OpenGL](https://www.mapbox.com/blog/drawing-antialiased-lines/)
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