如何在ThreeJs中绘制一个球体直径的线？

Question

假设我有一个像这样的球：

var geometry = new THREE.SphereGeometry(1, 32, 32); 
window.sphere = new THREE.Mesh(geometry, material); 
scene.add(window.sphere); 

我怎么会再画一个球体的直径围绕一条线吗？最好平行于x轴。这里的最终目标是结合文字使用这样一条线来说明尺寸（例如，这个球体是10米）。

Answer 1

您可以使用这一招：

var material = new THREE.MeshBasicMaterial({ color: 0xaaaaaa }); 
var geometry = new THREE.SphereGeometry(32, 32, 32); 
var sphere = new THREE.Mesh(geometry, material); 
scene.add(sphere); 

var geometry = new THREE.TorusGeometry(31.9, 0.16, 64, 100); 
var material = new THREE.MeshBasicMaterial({ color: 0xffff00 }); 
var torus = new THREE.Mesh(geometry, material); 
torus.rotation.x = Math.PI/2; 
scene.add(torus); 

http://jsfiddle.net/10hemttk/36/

UPD。好，这样更正确：

var rad = 32, 
    delta = 0.05, 
    segs = 64, 
    material = null, 
    geometry = null, 
    circle = null, 
    sphere = null; 

material = new THREE.LineBasicMaterial({ color: 0xffff00 }), 
geometry = new THREE.CircleGeometry(rad+delta, segs),  
geometry.vertices.shift(); 
circle = new THREE.Line(geometry, material); 
circle.rotation.x = Math.PI/2; 
scene.add(circle); 

material = new THREE.MeshBasicMaterial({ color: 0xaaaaaa }); 
geometry = new THREE.SphereGeometry(rad, segs, segs); 
sphere = new THREE.Mesh(geometry, material); 
scene.add(sphere);