Introduction to threejs

Introduction to three.js
https://github.com/Toronto-WebGL-Meetup/Talk_10-December-2015

About Me
● Gareth Marland (@garethmarland)
● British
● By day, Autodesk Revit Server
● By night, Dotstorming and Boardthing

Moving from 2D to 3D
● Traditional 2D web development is like creating
a shareable document
● 3D web development is like creating a
shareable movie scene

Creating your scene
● The light source
● The camera
● The renderer
Lights, Camera, Action!

The light source
● Ambient Light
– Applies a light globally. To every object in the scene
● Point Light
– Shines light in all directions and lights up anything that
is in range
● Directional Light
– The most commonly used lighting
– Works like a spotlight, in a position and shines in a
direction

Light source examples
● Ambient Light
var ambLight = new THREE.AmbientLight(0x404040);
scene.add(ambLight);
● Point Light
var pointLight = new THREE.PointLight(0x0033ff, 3, 150);
pointLight.position.set(70, 5, 70);
scene.add(pointLight);
● Directional Light
var dirLight = new THREE.DirectionalLight(0xffffff, 1);
dirLight.position.set(100, 100, 50);
scene.add(dirLight);

The camera
● Orthographic Camera
– Does not take a objects distance from the camera into
account when drawing
– Created with top, bottom, left, right, near and far
● Perspective Camera
– The most commonly used
– Takes an objects distance from he camera into account
– Created with fov, aspect ratio, near and far

The renderer
● Draws the scene
● Can be set up to loop in order to animate
● Needs to be attached to an HTML element
var renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setSize(containerWidth, containerHeight);
document.getElementById(“container”).appendChild(renderer.domElement);
var renderScene = function () {
requestAnimationFrame( renderScene );
renderer.render(scene, camera);
};
renderScene()

Putting it together
var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(75, containerWidth/containerHeight, 0.1, far);
scene.add(camera);
var pointLight = new THREE.PointLight(0xffffff, 1);
pointLight.position.set(0,5,5);
scene.add(pointLight);
var renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setSize(containerWidth, containerHeight);
document.getElementById(“container”).appendChild(renderer.domElement);
};
renderScene();

Creating an object
● Define the geometry
– Use a predefined three.js object
– Define your own vertices
– Use a modelling tool
● Define the material
– Basic
– Lambert
– Phong
– Custom
●
Create the mesh
●
Add it to the scene

Animating an object
● Should be updated within the rendering method
● The rendering only needs to be called when a
change needs to be made
var render = function () {
var that = this;
var updateScene = function() {
// Do your updates to the object here
}
updateScene();
};
renderScene();
}

Selecting objects
● Selecting needs to work differently in 3D
● We using something called “raycasting”
● It's basically shooting lazers in space and
seeing what we hit!

Selecting objects example
var mousePosition = new THREE.Vector2();
mousePosition.x = 2 * (mouseEvent.x / renderer.domElement.clientWidth) - 1;
mousePosition.y = 1 - 2 * (mouseEvent.y / renderer.domElement.clientHeight );
var raycaster = new THREE.Raycaster();
raycaster.setFromCamera(mousePosition, camera);
var intersected = raycaster.intersectObject(scene, true);

Controlling the camera
● Bind the camera to a mouse event
● Include a library such as OrbitControls.js

Advantages of the medium
● Can be opened in a browser
● Can be mixed and matched with other web
based technologies
– Websockets
– HTML Canvas
● Fairly easy to understand

Introduction to threejs

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Introduction to threejs