# How can I bind two shapes together as one in Three.js?

Can I bind two different shapes together as one shape?

For example, binding sphere and cylinder together as one?

Kind of, yes. There are multiple options:

1. via hierarchy you can simply add one mesh to another using the `add()` function
2. via the GeometryUtil’s `merge()` function to merge vertices and meshes of two Geometry objects into one
3. using a basic 3D editor that supports Boolean operations between meshes and exporting.

Method 1 is pretty straightforward:

``````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;
``````

Notice that 16 is repeated, so the subdivisions level in one mesh matches the other (for a decent look).

Method 2.1 – via GeometryUtils

``````// Make a sphere

var sg = new THREE.SphereGeometry(100, 16, 12);
// Make a 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 }));
``````

Method 2.2 merging a Lathe half-sphere and a cylinder:

``````var pts = []; // Points array

var detail = .1; // Half-circle detail - how many angle increments will be used to generate points
var total = Math.PI * .51;
for(var angle = 0.0; angle < total ; angle+= detail) // Loop from 0.0 radians to PI (0 - 180 degrees)

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;
``````

The one problem I can’t address at the moment comes from the faces that are inside the mesh. Ideally, those would have normals flipped, so they wouldn’t render, but I haven’t found a quick solution for that.

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The third is fairly straightforward. Most 3D packages allow Boolean operation on meshes (e.g., merging two meshes together with the ADD operation (meshA + meshB)). Try creating a cylinder and a sphere in Blender (free and opensource), which already has a Three.js exporter. Alternatively you can export an .obj file of the merged meshes from your 3D editor or choice and use the convert_obj_three script.

I’ve found yet another method, which might be easier/more intuitive. Remember the Boolean operations I’ve mentioned above?

It turns out there is an awesome JavaScript library just for that: Constructive Solid Geometry: Chandler Prall wrote some handy functions to connect CSG with three.js. So with the CSG library and the Three.js wrapper for it, you can simply do this:

``````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());
``````

Which gives you a nice result (no problems with extra faces/flipping normals, etc.):  The answers/resolutions are collected from stackoverflow, are licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0 .