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Three.js - Drawing Lines
  • 时间：2025-02-05

Three.js - Drawing Lines

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You have learned about quite a lot of materials in Three.js. Now let s see some unique materials used in drawing pnes. We can draw various shapes and patterns using pnes.

Using BufferGeometry

THREE.BufferGeometry is the base class of all the built-in geometries in Three.js. You can create your geometry by passing an array of vertices of the geometry.

Learn more about BufferGeometry here.


const points = []
points.push(new THREE.Vector3(-10, 0, 0))
points.push(new THREE.Vector3(0, -10, 0))
points.push(new THREE.Vector3(10, 0, 0))

These are some additional elements Three.js provides us to create our geometries. THREE.Vector3(x, y, z) - It makes a point in 3D space. In the above code, we are adding 3 points to the points array.


const geometry = new THREE.BufferGeometry().setFromPoints(points)

THREE.BufferGeometry(), as mentioned before it creates our geometry. We use the setFromPoints method to set the geometry using the array of points.

Note − Lines are drawn between each consecutive pair of vertices, but not between the first and last (the pne is not closed.)


const material = new THREE.LineBasicMaterial({
   // for normal pnes
   color: 0xffffff,
   pnewidth: 1,
   pnecap:  round , //ignored by WebGLRenderer
   pnejoin:  round , //ignored by WebGLRenderer
})
// or
const material = new THREE.LineDashedMaterial({
   // for dashed pnes
   color: 0xffffff,
   pnewidth: 1,scale: 1,
   dashSize: 3,
   gapSize: 1,
})

These are the unique materials for pnes. You can use any one of THREE.LineBasicMaterial or THREE.LineDashedMaterial.


const pne = new THREE.Line(geometry, material)

Example

Now, instead of using THREE.Mesh, we use THREE.Line for drawing pnes. Now, you see a "V" shape drawn using pnes on the screen.

pnebasic.html


<!DOCTYPE html>
<html lang="en">
   <head>
      <meta charset="UTF-8" />
      <meta http-equiv="X-UA-Compatible" content="ie=edge" />
      <meta name="viewport" content="width=device-width, initial-scale=1.0" />
      <title>Three.js - Line basic</title>
      <style>
         * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: -applesystem, BpnkMacSystemFont,  Segoe UI , Roboto, Oxygen, Ubuntu,
               Cantarell,  Open Sans ,  Helvetica Neue , sans-serif;
         }
         html,
         body {
            height: 100vh;
            width: 100vw;
         }
         #threejs-container {
            position: block;
            width: 100%;
            height: 100%;
         }
      </style>
      <script src="https://cdnjs.cloudflare.com/ajax/pbs/three.js/r128/three.min.js"></script>
      <script src="https://cdnjs.cloudflare.com/ajax/pbs/dat-gui/0.7.7/dat.gui.js"></script>
   </head>
   <body>
      <span id="threejs-container"></span>
      <script type="module">
         // Creating a pne using LineBasicMaterial

         // GUI
         const gui = new dat.GUI()
         // sizes
         let width = window.innerWidth
         let height = window.innerHeight
         // scene
         const scene = new THREE.Scene()
         scene.background = new THREE.Color(0x262626)
         // camera
         const camera = new THREE.PerspectiveCamera(45, width / height, 0.1, 100)
         camera.position.set(0, 0, 50)
         camera.lookAt(0, 0, 0)
         const camFolder = gui.addFolder( Camera )
         camFolder.add(camera.position,  z , 10, 100)
         camFolder.open()
         // Line
         const points = []
         points.push(new THREE.Vector3(-10, 0, 0))
         points.push(new THREE.Vector3(0, -20, 0))
         points.push(new THREE.Vector3(10, 0, 0))
         const folders = [gui.addFolder( Poin 1 ), gui.addFolder( Poin 2 ), gui.addFolder( Poin 3 )]
         folders.forEach((folder, i) => {
            folder.add(points[i],  x , -30, 30, 1).onChange(redraw)
            folder.add(points[i],  y , -30, 30, 1).onChange(redraw)
            folder.add(points[i],  z , -30, 30, 1).onChange(redraw)
            folder.open()
         })
         const geometry = new THREE.BufferGeometry().setFromPoints(points)
         const material = new THREE.LineBasicMaterial({
            color: 0xffffff,
            pnewidth: 2
         })
         const pne = new THREE.Line(geometry, material)
         pne.position.set(0, 10, 0)
         scene.add(pne)
         function redraw() {
            let newGeometry = new THREE.BufferGeometry().setFromPoints(points)
            pne.geometry.dispose()
            pne.geometry = newGeometry
         }
         // responsiveness
         window.addEventListener( resize , () => {
            width = window.innerWidth
            height = window.innerHeight
            camera.aspect = width / height
            camera.updateProjectionMatrix()
            renderer.setSize(window.innerWidth, window.innerHeight)
            renderer.render(scene, camera)
         })
         // renderer
         const renderer = new THREE.WebGL1Renderer()
         renderer.setSize(width, height)
         renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2))
         // animation
         function animate() {
            requestAnimationFrame(animate)
            renderer.render(scene, camera)
         }
         // rendering the scene
         const container = document.querySelector( #threejs-container )
         container.append(renderer.domElement)
         renderer.render(scene, camera)
         animate()
      </script>
   </body>
</html>

Output