javascript - 如何在ThreeJs中在球体直径上画一条线？

Question

假设我有一个像这样的球体:

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

然后我如何围绕球体的直径画一条线？优选地平行于x轴。这里的最终目标是使用这样一条线与文本结合来说明尺寸(例如，该球体的直径为 10m)。

Answer 1

你可以使用这个技巧:

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/

更新。嗯，这种方式更正确:

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 );