标签：图形 三维 webgl three.js javascript
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/BoxGeometry.js文件的注释.
更多更新在 : https://github.com/omni360/three.js.sourcecode
/**
* @author mrdoob / http://mrdoob.com/
* based on http://papervision3d.googlecode.com/svn/trunk/as3/trunk/src/org/papervision3d/objects/primitives/Cube.as
*/
/*
///BoxGeometry用来在三维空间内创建一个立方体盒子对象.
///
/// 用法: var geometry = new THREE.BoxGeometry(1,1,1);
/// var material = new THREE.MeshBasicMaterial({color: 0x00ff00});
/// var cube = new THREE.Mesh(geometry,material);
/// scene.add(cube);
*/
///<summary>BoxGeometry</summary>
///<param name ="width" type="float">立方体宽度</param>
///<param name ="height" type="float">立方体高度</param>
///<param name ="depth" type="float">立方体深度</param>
///<param name ="widthSegments" type="int">立方体宽度细分线段数</param>
///<param name ="heightSegments" type="int">立方体高度细分线段数</param>
///<param name ="depthSegments" type="int">立方体深度细分线段数</param>
THREE.BoxGeometry = function ( width, height, depth, widthSegments, heightSegments, depthSegments ) {
THREE.Geometry.call( this ); //调用Geometry对象的call方法,将原本属于Geometry的方法交给当前对象BoxGeometry来使用.
this.parameters = {
width: width,
height: height,
depth: depth,
widthSegments: widthSegments,
heightSegments: heightSegments,
depthSegments: depthSegments
};
this.widthSegments = widthSegments || 1;
this.heightSegments = heightSegments || 1;
this.depthSegments = depthSegments || 1;
var scope = this;
var width_half = width / 2;
var height_half = height / 2;
var depth_half = depth / 2;
buildPlane( 'z', 'y', - 1, - 1, depth, height, width_half, 0 ); // px
buildPlane( 'z', 'y', 1, - 1, depth, height, - width_half, 1 ); // nx
buildPlane( 'x', 'z', 1, 1, width, depth, height_half, 2 ); // py
buildPlane( 'x', 'z', 1, - 1, width, depth, - height_half, 3 ); // ny
buildPlane( 'x', 'y', 1, - 1, width, height, depth_half, 4 ); // pz
buildPlane( 'x', 'y', - 1, - 1, width, height, - depth_half, 5 ); // nz
///<summary>buildPlane</summary>
///<param name ="u" type="String">取值范围"x,y,z",表示从构建面的u坐标与xyz坐标的映射</param>
///<param name ="v" type="String">取值范围"x,y,z",表示从构建面的v坐标与xyz坐标的映射</param>
///<param name ="udir" type="float">为计算平面u方向上的顶点与原点的方向</param>
///<param name ="vdir" type="float">为计算平面v方向上的顶点与原点的方向</param>
///<param name ="width" type="float">立方体宽度</param>
///<param name ="height" type="float">立方体高度</param>
///<param name ="depth" type="float">立方体深度的一半(why?应为立方体是以中心点为原点!)</param>
///<param name ="materialIndex" type="int">材质索引号</param>
function buildPlane( u, v, udir, vdir, width, height, depth, materialIndex ) {
var w, ix, iy,
gridX = scope.widthSegments,
gridY = scope.heightSegments,
width_half = width / 2,
height_half = height / 2,
offset = scope.vertices.length;
//通过参数uv确定w坐标,用来确定面的方向,想象一下立方体有六个面,通过buildPlane来构建三角面.
if ( ( u === 'x' && v === 'y' ) || ( u === 'y' && v === 'x' ) ) {
w = 'z';
} else if ( ( u === 'x' && v === 'z' ) || ( u === 'z' && v === 'x' ) ) {
w = 'y';
gridY = scope.depthSegments;
} else if ( ( u === 'z' && v === 'y' ) || ( u === 'y' && v === 'z' ) ) {
w = 'x';
gridX = scope.depthSegments;
}
var gridX1 = gridX + 1,
gridY1 = gridY + 1,
segment_width = width / gridX,
segment_height = height / gridY,
normal = new THREE.Vector3();
normal[ w ] = depth > 0 ? 1 : - 1;
for ( iy = 0; iy < gridY1; iy ++ ) { //这里在构建几何体时非常重要,通过用户给定的参数,计算出顶点,这些顶点的顺序,要在下面使用.
//如果要自己定义几何体对象,计算顶点,和三角面是必不可少的.这里需要用户对顶点的存储顺序和面的构建顺序,在头脑中有清晰的几何形象.多做练习吧.
for ( ix = 0; ix < gridX1; ix ++ ) {
var vector = new THREE.Vector3();
vector[ u ] = ( ix * segment_width - width_half ) * udir;
vector[ v ] = ( iy * segment_height - height_half ) * vdir;
vector[ w ] = depth;
scope.vertices.push( vector ); //通过长宽高,方向,线段数计算出顶点的坐标.
}
}
for ( iy = 0; iy < gridY; iy ++ ) { //这里是构建几何体非常重要的一步,根据一个一个的三角面拼成立方体一个面
for ( ix = 0; ix < gridX; ix ++ ) {
//计算组成立方体面的矩形的四个顶点,a,b,c,d,我经常误理解为a,b,c,d,4条边,这里应该是学的几何知识影响的我.
var a = ix + gridX1 * iy;
var b = ix + gridX1 * ( iy + 1 );
var c = ( ix + 1 ) + gridX1 * ( iy + 1 );
var d = ( ix + 1 ) + gridX1 * iy;
var uva = new THREE.Vector2( ix / gridX, 1 - iy / gridY );
var uvb = new THREE.Vector2( ix / gridX, 1 - ( iy + 1 ) / gridY );
var uvc = new THREE.Vector2( ( ix + 1 ) / gridX, 1 - ( iy + 1 ) / gridY );
var uvd = new THREE.Vector2( ( ix + 1 ) / gridX, 1 - iy / gridY );
var face = new THREE.Face3( a + offset, b + offset, d + offset ); //构建的a,b,c3个顶点组成的三角面
face.normal.copy( normal );
face.vertexNormals.push( normal.clone(), normal.clone(), normal.clone() ); //计算面的法向量
face.materialIndex = materialIndex; //赋值面的材质索引
scope.faces.push( face );
scope.faceVertexUvs[ 0 ].push( [ uva, uvb, uvd ] );
face = new THREE.Face3( b + offset, c + offset, d + offset ); //构建的b,c,d,3个顶点组成的三角面,一个平面有两个三角面,都见过吧.
face.normal.copy( normal );
face.vertexNormals.push( normal.clone(), normal.clone(), normal.clone() ); //计算面的法向量
face.materialIndex = materialIndex; //赋值面的材质索引
scope.faces.push( face );
scope.faceVertexUvs[ 0 ].push( [ uvb.clone(), uvc, uvd.clone() ] );
}
}
}
this.mergeVertices(); //mergeVertices方法用来清理几何体中重复的顶点
};
/*************************************************
****下面是BoxGeometry对象的方法属性定义,继承自Geometry对象.
**************************************************/
THREE.BoxGeometry.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/BoxGeometry.js文件的注释.
更多更新在 : https://github.com/omni360/three.js.sourcecode
three.js 源码注释（六十八）extras/geometries/BoxGeometry.js
标签：图形 三维 webgl three.js javascript
原文地址：http://blog.csdn.net/omni360/article/details/43152431
