《Three.js 入门指南》3.1.1 - 基本几何形状 - 球体(SphereGeometry)
3.1 基本几何形状
球体(SphereGeometry)
构造函数:
THREE.SphereGeometry(radius, segmentsWidth, segmentsHeight, phiStart, phiLength, thetaStart, thetaLength)
radius:是半径;
segmentsWidth:经度上的切片数,相当于经度被切成了几瓣;
segmentsHeight:纬度上的切片数,相当于纬度被切成了几层;
phiStart:经度开始的弧度;
phiLength:经度跨过的弧度;
thetaStart:纬度开始的弧度;
thetaLength:纬度跨过的弧度。
分段
在图形底层的实现中,并没有曲线的概念,曲线都是由多个折线近似构成的。当折线越多,越近乎曲线。切片数决定了,图形的“精细度”
经度分段(切片demo)
维度分段(切片demo)
缺省值说明
phiStart、phiLength、thetaStart、thetaLength 这四个值是缺省值,即可以省略,而省略的时候实际有默认值,将画出一个完整的球体。通过不同的值修改,可以实现各种,不完整球体、球面。
例如:
THREE.SphereGeometry(2, 50, 50, Math.PI / 2, Math.PI)
(1/4 个球面)
球体的完整示例demo与效果:
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <script type="text/javascript" src="./three.js"></script> <title>Document</title> </head> <body onload="init()"> <canvas id="mainCanvas" width="800px" height="600px"></canvas> </body> <script> function init() { var renderer = new THREE.WebGLRenderer({ canvas: document.getElementById('mainCanvas') }); renderer.setClearColor(0x000000); var scene = new THREE.Scene(); var aspect = window.innerWidth / window.innerHeight; var camera = new THREE.OrthographicCamera(-2 * aspect, 2 * aspect, -1.5 * aspect, 1.5 * aspect, 1, 500); camera.position.set(200, 200, 200); scene.add(camera); camera.lookAt(new THREE.Vector3(0, 0, 0)); var cube = new THREE.Mesh(new THREE.SphereGeometry(2, 50, 50), new THREE.MeshBasicMaterial({ color: 0xff0000, wireframe: true }) ) scene.add(cube); renderer.render(scene, camera); } </script> </html>