如何在 ThreeJs 的球體直徑上畫一條線？

Question

假設我有一個這樣的球體：

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

那么我將如何在球體的直徑周圍畫一條線？ 優選平行於x軸。 此處的最終目標是將這樣的線條與文本結合使用以說明大小（例如，該球體的直徑為 10m）。

Answer 1

你可以使用這個技巧：

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。 好吧，這種方式更正確：

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 );