ThreeJS:将边缘几何应用于ArrowHelper

Question

我正在尝试使用ArrowHelper在ThreeJS中创建一个箭头：

let arrow = new THREE.ArrowHelper(direction.normalize(), new THREE.Vector3(), length, color, headLength, headWidth);

另外，我想用一个单独的颜色作为边缘。我意识到我需要使用THREE.EdgesGeometry，但是我不太明白如何应用它。有人能帮我吗？

更新很抱歉混淆了，我以为箭头使用金字塔，而不是锥。有没有一种方法可以用金字塔代替圆锥，用不同的颜色来代替边缘呢？

更新

谢谢你们的回答，他们真的很有帮助。最后我创建了自定义箭头类(从ArrowHelper复制了大部分代码)：

class CustomArrow extends THREE.Object3D {

    constructor( dir, origin, length, color, edgeColor, headLength, headWidth ) {

        super();
        // dir is assumed to be normalized

        this.type = 'CustomArrow';

        if ( dir === undefined ) dir = new THREE.Vector3( 0, 0, 1 );
        if ( origin === undefined ) origin = new THREE.Vector3( 0, 0, 0 );
        if ( length === undefined ) length = 1;
        if ( color === undefined ) color = 0xffff00;
        if ( headLength === undefined ) headLength = 0.2 * length;
        if ( headWidth === undefined ) headWidth = 0.2 * headLength;

        if ( this._lineGeometry === undefined ) {
            this._lineGeometry = new THREE.BufferGeometry();
            this._lineGeometry.setAttribute( 'position', new THREE.Float32BufferAttribute( [ 0, 0, 0, 0, 1, 0 ], 3 ) );
            this._coneGeometry = new THREE.ConeBufferGeometry( 0.5, 1, 6);
            this._coneGeometry.translate( 0, - 0.5, 0 );
            this._axis = new THREE.Vector3();
        }

        this.position.copy( origin );

        this.line = new THREE.Line( this._lineGeometry, new THREE.LineBasicMaterial( { color: color, toneMapped: false, linewidth: 4 } ) );
        this.line.matrixAutoUpdate = false;
        this.add( this.line )

        // base material        
        this.cone = new THREE.Mesh( this._coneGeometry, new THREE.MeshBasicMaterial( { color: color, toneMapped: false } ) );
        this.add(this.cone);

        // wire frame
        this.wireframe = new THREE.Mesh( this._coneGeometry, new THREE.MeshBasicMaterial( { 
            color: edgeColor, 
            toneMapped: false, 
            wireframe: true,
            wireframeLinewidth: 2 } ) );
        this.add(this.wireframe);

        this.setDirection( dir );
        this.setLength( length, headLength, headWidth );
    }

    setDirection( dir ) {

        // dir is assumed to be normalized

        if ( dir.y > 0.99999 ) {

            this.quaternion.set( 0, 0, 0, 1 );

        } else if ( dir.y < - 0.99999 ) {

            this.quaternion.set( 1, 0, 0, 0 );

        } else {

            this._axis.set( dir.z, 0, - dir.x ).normalize();

            const radians = Math.acos( dir.y );

            this.quaternion.setFromAxisAngle( this._axis, radians );

        }

    }

    setLength( length, headLength, headWidth ) {

        if ( headLength === undefined ) headLength = 0.2 * length;
        if ( headWidth === undefined ) headWidth = 0.2 * headLength;

        this.line.scale.set( 1, Math.max( 0.0001, length - headLength ), 1 ); // see #17458
        this.line.updateMatrix();
        
        this.cone.scale.set( headWidth, headLength, headWidth );
        this.cone.position.y = length;
        this.cone.updateMatrix();
        
        this.wireframe.scale.set( headWidth, headLength, headWidth );
        this.wireframe.position.y = length;
        this.wireframe.updateMatrix();
    }

    setColor( color ) {
        this.line.material.color.set( color );
        // this.cone.material.color.set( color );
        // this.wireframe.material.color.set( color );
    }

    copy( source ) {
        super.copy( source, false );
        this.line.copy( source.line );
        this.cone.copy( source.cone );
        this.wireframe.copy( source.wireframe );
        return this;
    }
}

由于某些原因，线宽和wireframeLinewidth不影响线宽。知道为什么吗？

Answer 1

编辑:金字塔是一个包含4个径向段的圆锥，如果您想这样做的话，看看阿罗海珀如何构造它的锥(它是用锥形的CylinderGeometry构造的)和基于参数的直线，然后用如下所构造的锥几何来替换它：

原件：

_coneGeometry = new CylinderBufferGeometry( 0, 0.5, 1, 5, 1 );

新：

_coneGeometry = new ConeBufferGeometry( 0.5, 1, 4);

然后，您不必使用EdgesGeometry，而是使用有线框架材料选项(per @Pricer849的注释)：

let wireframeMaterial = new THREE.MeshBasicMaterial({color: "aqua", wireframe: true});

let coneEdgeMesh = new THREE.Mesh(_coneGeometry, wireframeMaterial);

原来的答案：

THREE.ArrowHelper由两个Object3Ds组成:一个THREE.Line表示直线，一个THREE.Mesh表示箭头锥。这条线的几何只包含两个点，没有边，因为它是一条线，但是对于圆锥，你可以使用：

let coneEdgeGeometry = new THREE.EdgesGeometry(arrow.cone.geometry);

然后构造一个具有边缘几何和所需颜色的LineSegments对象：

let line = new THREE.LineSegments( coneEdgeGeometry, new THREE.LineBasicMaterial( { color: 0xffffff } ) );
arrow.add(line);

如果没有显示锥边，请尝试将THREE.LineSegments的THREE.LineSegments设置为-1 (这可能会导致其他问题)。

Answer 2

你可以这样改变箭头锥的颜色：

​

body {
  overflow: hidden;
  margin: 0;
}

<script type="module">
  import * as THREE from "https://threejs.org/build/three.module.js";     
  import {OrbitControls} from "https://threejs.org/examples/jsm/controls/OrbitControls.js"; 
  
  let scene = new THREE.Scene(); 
  let camera = new THREE.PerspectiveCamera(60, innerWidth / innerHeight,
  1, 100); 
  camera.position.set(0, 5, 10); 
  let renderer = new THREE.WebGLRenderer(); 
  renderer.setSize(innerWidth, innerHeight); 
  document.body.appendChild(renderer.domElement); 
  
  new OrbitControls(camera, renderer.domElement); 
  
  scene.add(new THREE.GridHelper());
  
  // different colors 
  let ah = new THREE.ArrowHelper( 
    new THREE.Vector3(0, 1, 0), 
    new THREE.Vector3(-4, 0, 0), 
    5, 
    "magenta" /* default colour */); 
  ah.cone.material.color.set("red"); // change color of cone
  scene.add(ah); 
  
  // colourful pyramid
  let cg = new THREE.SphereBufferGeometry(0.5, 4, 2).toNonIndexed();
  let pos = cg.attributes.position;
  for (let i = 0; i < pos.count; i++){
    if (pos.getY(i) < 0) pos.setY(i, 0);
  }
  console.log(cg);
  let cls = [
    new THREE.Color("red"),
    new THREE.Color("green"),
    new THREE.Color("blue"),
    new THREE.Color("yellow")
  ]
  let colors = [];
  for(let i = 0; i < 2; i++){
    cls.forEach( (c) => {
      colors.push(c.r, c.g, c.b);
      colors.push(c.r, c.g, c.b);
      colors.push(c.r, c.g, c.b);
    });
  }
  cg.setAttribute("color", new THREE.Float32BufferAttribute(colors, 3));
  
  let cm = new THREE.MeshBasicMaterial({vertexColors: true});
  let co = new THREE.Mesh(cg, cm);
  co.scale.set(1, 5, 1);
  scene.add(co);
  
  renderer.setAnimationLoop(()=>{ 
    renderer.render(scene, camera); 
  });
</script>

​