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Choosing the a bcd
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09.

Difficulty Hard

## Introduction 00:00

Until now, we only used the BoxGeometry class to create our cube. In this lesson, we will discover various other geometries, but first, we need to understand what a geometry really is.

## What is a geometry? 00:25

In Three.js, geometries are composed of vertices (point coordinates in 3D spaces) and faces (triangles that join those vertices to create a surface).

We use geometries to create meshes, but you can also use geometries to form particles. Each vertex (singular of vertices) will correspond to a particle, but this is for a future lesson.

We can store more data than the position in the vertices. A good example would be to talk about the UV coordinates or the normals. As you'll see, we will learn more about those later.

## The different built-in geometries 03:22

Three.js has many built-in geometries. While you don't need to know precisely how to instantiate each one, it is good to know that they exist.

All the built-in geometries we are going to see inherit from the BufferGeometry class. This class has many built in methods like `translate(...)`, `rotateX(...)`, `normalize()`, etc. but we are not going to use them in this lesson.

Most of the geometries documentation pages have examples.

• BoxGeometry To create a box.
• PlaneGeometry To create a rectangle plane.
• CircleGeometry To create a disc or a portion of a disc (like a pie chart).
• ConeGeometry To create a cone or a portion of a cone. You can open or close the base of the cone.
• CylinderGeometry To create a cylinder. You can open or close the ends of the cylinder and you can change the radius of each end.
• RingGeometry To create a flat ring or portion of a flat circle.
• TorusGeometry To create a ring that has a thickness (like a donut) or portion of a ring.
• TorusKnotGeometry To create some sort of knot geometry.
• DodecahedronGeometry To create a 12 faces sphere. You can add details for a rounder sphere.
• OctahedronGeometry To create a 8 faces sphere. You can add details for a rounder sphere.
• TetrahedronGeometry To create a 4 faces sphere (it won't be much of a sphere if you don't increase details). You can add details for a rounder sphere.
• IcosahedronGeometry To create a sphere composed of triangles that have roughly the same size.
• SphereGeometry To create the most popular type of sphere where faces looks like quads (quads are just a combination of two triangles).
• ShapeGeometry To create a shape based on a path.
• TubeGeometry To create a tube following a path.
• ExtrudeGeometry To create an extrusion based on a path. You can add and control the bevel.
• LatheGeometry To create a vase or portion of a vase (more like a revolution).
• TextGeometry To create a 3D text. You'll have to provide the font in typeface json format.

If you need a particular geometry that is not supported by Three.js, you can create your own geometry in JavaScript, or you can make it in a 3D software, export it and import it into your project. We will learn more about that later.

## Box example 10:47

We already made a cube but we didn't talk much about the parameters. Most geometries have parameters, and you should always take a look at the documentation before using it.

The BoxGeometry has 6 parameters:

• `width`: The size on the `x` axis
• `height`: The size on the `y` axis
• `depth`: The size on the `z` axis
• `widthSegments`: How many subdivisions in the `x` axis
• `heightSegments`: How many subdivisions in the `y` axis
• `depthSegments`: How many subdivisions in the `z` axis

Subdivisions correspond to how much triangles should compose the face. By default it's `1`, meaning that there will only be 2 triangles per face. If you set the subdivision to `2`, you'll end up with 8 triangles per face:

``const geometry = new THREE.BoxGeometry(1, 1, 1, 2, 2, 2)``

The problem is that we cannot see these triangles.

A good solution is to add `wireframe: true` to our material. The wireframe will show the lines that delimit each triangle:

``const material = new THREE.MeshBasicMaterial({ color: 0xff0000, wireframe: true })`` As you can see, there are 8 triangles by face.

While this is not relevant for a flat face cube, it gets more interesting when using a SphereGeometry:

``const geometry = new THREE.SphereGeometry(1, 32, 32)`` The more subdivisions we add, the less we can distinguish the faces. But keep in mind that too many vertices and faces will affect performances.

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Next lesson

## How to use it 🤔

• Run `npm install` to install dependencies
• Run `npm run dev` to launch the local server