three.js 源码注释（六十七）objects/PointCloud.js

/** * @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. */ ///PointCloud///Geometry对象点云对象里的点集合///PointCloudMaterial对象(点云材质对象)///返回Mesh对象THREE.PointCloud = function ( geometry, material ) { THREE.Object3D.call( this ); //调用Object3D对象的call方法,将本来属于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,将创建随机色彩材质,赋值给当前PointCloud对象 this.sortParticles = false; //设置是不是排序粒子?? //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方法用来取得当前对象与射线（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常常会用到,判断当前鼠标是不是与对象重适用来选择对象. /// NOTE：raycast方法中参数intersects参数用来存储交点的集合，格式以下 /// intersects.push( { /// /// distance: distance, /// point: intersectionPoint, /// indices: [ a, b, c ], /// face: null, /// faceIndex: null, /// object: this /// /// } ); /// *////raycast///射线对象///交点的属性集合///交点的属性集合THREE.PointCloud.prototype.raycast = ( function () { var inverseMatrix = new THREE.Matrix4(); //声明1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不是碰撞的具体实现. 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3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1个PointCloud点云对象. */ ///clone///接收克隆的Object3D对象///返回PointCloud对象.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换.用法和THREE.PointCloud对象1样. THREE.ParticleSystem = function ( geometry, material ) { console.warn( 'THREE.ParticleSystem has been renamed to THREE.PointCloud.' ); return new THREE.PointCloud( geometry, material ); };