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objects/PointCloud.js文件的注释.
更多更新在 : https://github.com/omni360/three.js.sourcecode
/**
* @author alteredq / http://alteredqualia.com/
*/
/*
///PointCloud点云对象,在场景中方便的改变大量的点精灵对象大小,位置等属性.
*/
///<summary>PointCloud</summary>
///<param name ="geometry" type="THREE.Geometry">Geometry对象点云对象里的点集合</param>
///<param name ="material" type="THREE.PointCloudMaterial">PointCloudMaterial对象(点云材质对象)</param>
///<returns type="PointCloud">返回Mesh对象</returns>
THREE.PointCloud = function ( geometry, material ) {
THREE.Object3D.call( this );//调用Object3D对象的call方法,将原本属于Object3D的方法交给当前对象PointCloud来使用.
this.geometry = geometry !== undefined ? geometry : new THREE.Geometry();////将参数geometry赋值给mesh对象的geometry属性
this.material = material !== undefined ? material : new THREE.PointCloudMaterial( { color: Math.random() * 0xffffff } );//将参数material赋值给PointCloud对象的material属性,如果没有传递material参数,将创建随机颜色材质,赋值给当前PointCloud对象
this.sortParticles = false;//设置是否排序粒子??
//TODO:sortParticles属性没有弄明白,有时间回来处理.
};
/*************************************************
****下面是PointCloud对象的方法属性定义,继承自Object3D
**************************************************/
THREE.PointCloud.prototype = Object.create( THREE.Object3D.prototype );
/*
///raycast方法用来获得当前对象与射线（参数raycaster）的交点.raycaster.intersectObject会调用这个方法。主要是用来进行碰撞检测,
/// 在选择场景中的对象时经常会用到,判断当前鼠标是否与对象重合用来选择对象.
/// NOTE：raycast方法中参数intersects参数用来存储交点的集合，格式如下
///intersects.push( {
///
///distance: distance,
///point: intersectionPoint,
///indices: [ a, b, c ],
///face: null,
///faceIndex: null,
///object: this
///
///} );
///
*////<summary>raycast</summary>
///<param name ="raycaster" type="THREE.Raycaster">射线对象</param>
///<param name ="intersects" type="ObjectArray">交点的属性集合</param>
///<returns type="ObjectArray">交点的属性集合</returns>
THREE.PointCloud.prototype.raycast = ( function () {
var inverseMatrix = new THREE.Matrix4();//声明一个4x4矩阵，用来放置逆矩阵
var ray = new THREE.Ray();//声明全局射线对象
return function ( raycaster, intersects ) {
var object = this;
var geometry = object.geometry;
var threshold = raycaster.params.PointCloud.threshold;
inverseMatrix.getInverse( this.matrixWorld );
ray.copy( raycaster.ray ).applyMatrix4( inverseMatrix );
if ( geometry.boundingBox !== null ) {
if ( ray.isIntersectionBox( geometry.boundingBox ) === false ) {
return;
}
}
var localThreshold = threshold / ( ( this.scale.x + this.scale.y + this.scale.z ) / 3 );
var position = new THREE.Vector3();
//检查射线与点云元素是否碰撞的具体实现.
var testPoint = function ( point, index ) {
var rayPointDistance = ray.distanceToPoint( point );
if ( rayPointDistance < localThreshold ) {
var intersectPoint = ray.closestPointToPoint( point );
intersectPoint.applyMatrix4( object.matrixWorld );
var distance = raycaster.ray.origin.distanceTo( intersectPoint );
intersects.push( {
distance: distance,
distanceToRay: rayPointDistance,
point: intersectPoint.clone(),
index: index,
face: null,
object: object
} );
}
};
//如果geometry对象是BufferGeometry对象
if ( geometry instanceof THREE.BufferGeometry ) {
var attributes = geometry.attributes;
var positions = attributes.position.array;
//下面对三种数据格式的pointCloud对象的元素进行检测.
if ( attributes.index !== undefined ) {
var indices = attributes.index.array;
var offsets = geometry.offsets;
if ( offsets.length === 0 ) {
var offset = {
start: 0,
count: indices.length,
index: 0
};
offsets = [ offset ];
}
for ( var oi = 0, ol = offsets.length; oi < ol; ++oi ) {
var start = offsets[ oi ].start;
var count = offsets[ oi ].count;
var index = offsets[ oi ].index;
for ( var i = start, il = start + count; i < il; i ++ ) {
var a = index + indices[ i ];
position.set(
positions[ a * 3 ],
positions[ a * 3 + 1 ],
positions[ a * 3 + 2 ]
);
testPoint( position, a );
}
}
} else {
var pointCount = positions.length / 3;
for ( var i = 0; i < pointCount; i ++ ) {
position.set(
positions[ 3 * i ],
positions[ 3 * i + 1 ],
positions[ 3 * i + 2 ]
);
testPoint( position, i );
}
}
} else {
var vertices = this.geometry.vertices;
for ( var i = 0; i < vertices.length; i ++ ) {
testPoint( vertices[ i ], i );
}
}
};
}() );
/*clone方法
///clone方法克隆一个PointCloud点云对象.
*/
///<summary>clone</summary>
///<param name ="object" type="PointCloud">接收克隆的Object3D对象</param>
///<returns type="PointCloud">返回PointCloud对象.</returns>
THREE.PointCloud.prototype.clone = function ( object ) {
if ( object === undefined ) object = new THREE.PointCloud( this.geometry, this.material );
object.sortParticles = this.sortParticles;
THREE.Object3D.prototype.clone.call( this, object );//继承Object3D的clone方法
return object;//返回克隆的PointCloud对象
};
// Backwards compatibility 向后兼容,粒子系统呗点云对象替代.用法和THREE.PointCloud对象一样.
THREE.ParticleSystem = function ( geometry, material ) {
console.warn( 'THREE.ParticleSystem has been renamed to THREE.PointCloud.' );
return new THREE.PointCloud( geometry, material );
};
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objects/PointCloud.js文件的注释.