商域无疆 (http://blog.csdn.net/omni360/)
本文遵循“署名-非商业用途-保持一致”创作公用协议
转载请保留此句：商域无疆 - 本博客专注于 敏捷开发及移动和物联设备研究：数据可视化、GOLANG、Html5、WEBGL、THREE.JS，否则，出自本博客的文章拒绝转载或再转载，谢谢合作。
俺也是刚开始学,好多地儿肯定不对还请见谅.
以下代码是THREE.JS 源码文件中extras/geometries/CircleGeometry.js文件的注释.
更多更新在 : https://github.com/omni360/three.js.sourcecode
/**
* @author hughes
*/
/*
///CircleGeometry用来在三维空间内创建一个圆形对象,因为圆形对象是由参数segments指定的一个个三角形围绕圆心拼接而成,所以也可以是多边形对象.
///
/// 用法: var radius = 5, segments = 32;
/// var geometry = new THREE.CircleGeometry(radius,segments);
/// var material = new THREE.MeshBasicMaterial({color: 0x00ff00});
/// var circle = new THREE.Mesh(geometry,material);
/// scene.add(circle);
*/
///<summary>CircleGeometry</summary>
///<param name ="radius" type="float">圆形(多边形)对象的半径,默认初始化为50</param>
///<param name ="segments" type="int">可选参数,圆形(多边形)的线段数(边数),默认初始化为8</param>
///<param name ="thetaStart" type="int">可选参数,圆(多边形)的起始点,默认初始化为0</param>
///<param name ="thetaLength" type="int">可选参数,圆(多边形)的结束点,默认初始化为Math.PI * 2</param>
THREE.CircleGeometry = function ( radius, segments, thetaStart, thetaLength ) {
THREE.Geometry.call( this );
this.parameters = {
radius: radius,
segments: segments,
thetaStart: thetaStart,
thetaLength: thetaLength
};
radius = radius || 50; //圆形(多边形)半径,默认初始化为50.
segments = segments !== undefined ? Math.max( 3, segments ) : 8; ///圆形或者多边形的线段数,最小为3,如果没有设置segments属性,则初始化为8.
thetaStart = thetaStart !== undefined ? thetaStart : 0; //圆形或者多边形的起始点,默认初始化为0.
thetaLength = thetaLength !== undefined ? thetaLength : Math.PI * 2; //圆(多边形)的结束点,默认初始化为Math.PI * 2
// 下面这段代码为圆形(多边形)生成uv坐标,点点信息.
var i, uvs = [],
center = new THREE.Vector3(), centerUV = new THREE.Vector2( 0.5, 0.5 );
this.vertices.push(center);
uvs.push( centerUV );
for ( i = 0; i <= segments; i ++ ) { //遍历组成圆形(多边形)的线段数或边数
var vertex = new THREE.Vector3();
var segment = thetaStart + i / segments * thetaLength; //获得组成圆形(多边形)边或线段的角度
vertex.x = radius * Math.cos( segment ); //根据半径和角度值计算出x坐标
vertex.y = radius * Math.sin( segment ); //根据半径和角度值计算出y坐标
this.vertices.push( vertex ); //添加到顶点数组.
uvs.push( new THREE.Vector2( ( vertex.x / radius + 1 ) / 2, ( vertex.y / radius + 1 ) / 2 ) ); //添加uvs坐标信息
}
var n = new THREE.Vector3( 0, 0, 1 );
for ( i = 1; i <= segments; i ++ ) { //遍历组成圆形(多边形)的线段数或边数
this.faces.push( new THREE.Face3( i, i + 1, 0, [ n.clone(), n.clone(), n.clone() ] ) ); //生成三角面的顶点索引
this.faceVertexUvs[ 0 ].push( [ uvs[ i ].clone(), uvs[ i + 1 ].clone(), centerUV.clone() ] ); //生成与三角面的顶点索引顺序相同的三角面的uvs坐标
}
this.computeFaceNormals(); //计算面法线
this.boundingSphere = new THREE.Sphere( new THREE.Vector3(), radius ); //生成圆形(多边形)对象的球形边界.
};
/*************************************************
****下面是CircleGeometry对象的方法属性定义,继承自Geometry对象.
**************************************************/
THREE.CircleGeometry.prototype = Object.create( THREE.Geometry.prototype );
商域无疆 (http://blog.csdn.net/omni360/)
本文遵循“署名-非商业用途-保持一致”创作公用协议
转载请保留此句：商域无疆 - 本博客专注于 敏捷开发及移动和物联设备研究：数据可视化、GOLANG、Html5、WEBGL、THREE.JS，否则，出自本博客的文章拒绝转载或再转载，谢谢合作。
以下代码是THREE.JS 源码文件中extras/geometries/CircleGeometry.js文件的注释.
更多更新在 : https://github.com/omni360/three.js.sourcecode
three.js 源码注释（六十九）extras/geometries/CircleGeometry.js
原文地址：http://blog.csdn.net/omni360/article/details/43152461
