Question

我是three.js世界的新手...... 我的问题是：我可以将两种不同的形状绑定在一起作为一个形状吗？例如，将球体和圆柱体绑定在一起？

Answer 1

有，是的，有多种选择：

via hierarchy您可以使用add()函数
通过GeometryUtil的merge()函数将两个Geometry对象的顶点和网格合并为一个
使用支持网格和导出之间的布尔运算的基本3D编辑器。

方法1非常简单：

var sphere = new THREE.Mesh( new THREE.SphereGeometry(100,16,12),new THREE.MeshLambertMaterial( { color: 0x2D303D, wireframe: true, shading: THREE.FlatShading } ));
                var cylinder = new THREE.Mesh(new THREE.CylinderGeometry(100, 100, 200, 16, 4, false ),new THREE.MeshLambertMaterial( { color: 0x2D303D, wireframe: true, shading: THREE.FlatShading } ));
                cylinder.position.y = -100;
                scene.add(sphere);
                scene.add(cylinder);

请注意，16会重复，因此一个网格中的细分级别与另一个网格中的细分级别相匹配（为了看起来不错）

方法2.1 - 通过GeometryUtils

//make a sphere
                var sg = new THREE.SphereGeometry(100,16,12);
                //make cylinder - ideally the segmentation would be similar to predictable results
                var cg = new THREE.CylinderGeometry(100, 100, 200, 16, 4, false );
                //move vertices down for cylinder, so it maches half the sphere - offset pivot
                for(var i = 0 ; i < cg.vertices.length; i++) cg.vertices[i].position.y -= 100;
                //merge meshes
                THREE.GeometryUtils.merge(sg,cg);
                var mesh = new THREE.Mesh( sg,new THREE.MeshLambertMaterial( { color: 0x2D303D, wireframe: true, shading: THREE.FlatShading } ));
                scene.add(mesh);

方法2.2合并Lathe half-sphere和圆柱体：

var pts = [];//points array
                var detail = .1;//half-circle detail - how many angle increments will be used to generate points
                var radius = 100;//radius for half_sphere
                var total = Math.PI * .51;
                for(var angle = 0.0; angle < total ; angle+= detail)//loop from 0.0 radians to PI (0 - 180 degrees)
                    pts.push(new THREE.Vector3(0,Math.cos(angle) * radius,Math.sin(angle) * radius));//angle/radius to x,z
                var lathe = new THREE.LatheGeometry( pts, 16 );//create the lathe with 12 radial repetitions of the profile
                //rotate vertices in lathe geometry by 90 degrees
                var rx90 = new THREE.Matrix4();
                rx90.setRotationFromEuler(new THREE.Vector3(-Math.PI * .5,0,0));
                lathe.applyMatrix(rx90);
                //make cylinder - ideally the segmentation would be similar for predictable results
                var cg = new THREE.CylinderGeometry(100, 100, 200, 16, 4, false );
                //move vertices down for cylinder, so it maches half the sphere
                for(var i = 0 ; i < cg.vertices.length; i++) cg.vertices[i].position.y -= 100;
                //merge meshes
                THREE.GeometryUtils.merge(lathe,cg);
                var mesh = new THREE.Mesh( lathe, new THREE.MeshLambertMaterial( { color: 0x2D303D, wireframe: true, shading: THREE.FlatShading } ) );
                mesh.position.y = 150;
                scene.add(mesh);

目前我无法解决的一个问题来自网格内部的面。理想情况下，那些会翻转法线以便它们不会渲染，但是没有找到快速解决方案。

第三是相当直接的。大多数3D软件包允许对网格进行布尔运算（例如，将两个网格与ADD运算（meshA + meshB）合并在一起）。尝试在Blender（free，opensource）中创建一个圆柱体和一个球体，它已经有一个three.js导出器。或者，您可以从3d编辑器或选项中导出合并网格的.obj文件，并使用convert_obj_three脚本。

<强>更新

我发现了另一种方法，可能更容易/更直观。还记得我上面提到的布尔运算吗？

原来有一个非常棒的js库：Constructive Solid Geometry：

CSG library preview from owner's github page

Chandler Prall写了一些方便的函数来连接CSG with three.js。因此，使用CSG库和three.js wrapper for it，您只需执行此操作：

var cylinder = THREE.CSG.toCSG(new THREE.CylinderGeometry(100, 100, 200, 16, 4, false ),new THREE.Vector3(0,-100,0));
var sphere   = THREE.CSG.toCSG(new THREE.SphereGeometry(100,16,12));
var geometry = cylinder.union(sphere);
var mesh     = new THREE.Mesh(THREE.CSG.fromCSG( geometry ),new THREE.MeshNormalMaterial());

这会给你一个很好的结果（额外的面孔没有问题/翻转法线/等等）：

cylinder-sphere union with CSG and three.js

Answer 2

我更新了THREE.js r62的包装器，你可以在这里找到它：https://github.com/kraag22/csg-wrapper

Three.js - 将两个形状绑定为一个？

2 个答案: