How to show only edge lines in three.js?

Question

I want to show lines only on the edges. Here I have included my output model which I tried using edgeGeometry and LinebasicMaterial. I want to remove the inner edge lines and show only outline edges

Answer 1

You can use EdgesGeometry

You pass it some other geometry and a threshold angle

  // only show edges with 15 degrees or more angle between faces
  const thresholdAngle = 15;
  const lineGeometry = new THREE.EdgesGeometry(geometry, thresholdAngle));

'use strict';

/* global THREE */

function main() {
  const canvas = document.querySelector('#c');
  const renderer = new THREE.WebGLRenderer({canvas});

  const fov = 40;
  const aspect = 2;  // the canvas default
  const near = 0.1;
  const far = 1000;
  const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
  camera.position.z = 20;

  const scene = new THREE.Scene();
  scene.background = new THREE.Color(0xAAAAAA);
  let solidMesh;

  {
    const color = 0xFFFFFF;
    const intensity = 1;
    const light = new THREE.DirectionalLight(color, intensity);
    light.position.set(-1, 2, 4);
    scene.add(light);
  }
  {
    const color = 0xFFFFFF;
    const intensity = 1;
    const light = new THREE.DirectionalLight(color, intensity);
    light.position.set(1, -2, -4);
    scene.add(light);
  }

  const objects = [];
  const spread = 15;

  function addObject(x, y, obj) {
    obj.position.x = x * spread;
    obj.position.y = y * spread;

    scene.add(obj);
    objects.push(obj);
  }

  function createMaterial() {
    const material = new THREE.MeshPhongMaterial({
      side: THREE.DoubleSide,
    });

    const hue = Math.random();
    const saturation = 1;
    const luminance = .5;
    material.color.setHSL(hue, saturation, luminance);

    return material;
  }

  function addSolidGeometry(x, y, geometry) {
    const mesh = new THREE.Mesh(geometry, createMaterial());
    addObject(x, y, mesh);
    return mesh;
  }

  function addLineGeometry(x, y, geometry) {
    const material = new THREE.LineBasicMaterial({color: 0x000000});
    const mesh = new THREE.LineSegments(geometry, material);
    addObject(x, y, mesh);
    return mesh;
  }

  {
    const shape = new THREE.Shape();
    const x = -2.5;
    const y = -5;
    shape.moveTo(x + 2.5, y + 2.5);
    shape.bezierCurveTo(x + 2.5, y + 2.5, x + 2, y, x, y);
    shape.bezierCurveTo(x - 3, y, x - 3, y + 3.5, x - 3, y + 3.5);
    shape.bezierCurveTo(x - 3, y + 5.5, x - 1.5, y + 7.7, x + 2.5, y + 9.5);
    shape.bezierCurveTo(x + 6, y + 7.7, x + 8, y + 4.5, x + 8, y + 3.5);
    shape.bezierCurveTo(x + 8, y + 3.5, x + 8, y, x + 5, y);
    shape.bezierCurveTo(x + 3.5, y, x + 2.5, y + 2.5, x + 2.5, y + 2.5);

    const extrudeSettings = {
      steps: 2,
      depth: 2,
      bevelEnabled: true,
      bevelThickness: 1,
      bevelSize: 1,
      bevelSegments: 2,
    };
    
    const geometry = new THREE.ExtrudeBufferGeometry(shape, extrudeSettings);

    solidMesh = addSolidGeometry(0, 0, geometry);
    const thresholdAngle = 15;
    addLineGeometry(0, 0, new THREE.EdgesGeometry(geometry, thresholdAngle));
  }

  function resizeRendererToDisplaySize(renderer) {
    const canvas = renderer.domElement;
    const width = canvas.clientWidth;
    const height = canvas.clientHeight;
    const needResize = canvas.width !== width || canvas.height !== height;
    if (needResize) {
      renderer.setSize(width, height, false);
    }
    return needResize;
  }

  function render(time) {
    time *= 0.001;

    if (resizeRendererToDisplaySize(renderer)) {
      const canvas = renderer.domElement;
      camera.aspect = canvas.clientWidth / canvas.clientHeight;
      camera.updateProjectionMatrix();
    }
    
    solidMesh.visible = (time | 0) % 2 !== 0;

    objects.forEach((obj, ndx) => {
      const speed = .1 + ndx * .0;
      const rot = time * speed;
      obj.rotation.x = rot;
      obj.rotation.y = rot;
    });

    renderer.render(scene, camera);

    requestAnimationFrame(render);
  }

  requestAnimationFrame(render);
}

main();

body {
  margin: 0;
}
#c {
  width: 100vw;
  height: 100vh;
  display: block;
}

<canvas id="c"></canvas>
  <script src="https://threejsfundamentals.org/threejs/resources/threejs/r108/build/three.min.js"></script>