《一塊兒來學three.js構建WebGL應用》第一課

時間 2019-12-04

標籤一塊兒 three.js 構建 webgl 應用一課欄目 JavaScript 简体版

原文原文鏈接

是時候開始咱們致力於WebGL的新系列文章。這是咱們的第一節課，咱們主要作些的基本功能：建立一個場景，相機，渲染器，控制器（OrbitControls）。咱們也將建立簡單的定向光，加上一些對象（不一樣的幾何形狀）的陰影。爲了使事情更快，咱們決定採起一個最流行的WebGL框架——three.js。爲何使用three.js？事實上，它是開源的JavaScript框架，它也是增加最迅速的和討論很熱烈的引擎。在這裏，已經準備了不少會用到的東西，從基本的點和向量，到作準備工做的場景、着色器，甚至立體效果。css

Live Demohtml

HTML

咱們能夠省略這一步，可是，一般，咱們在每一節課都會作。這是咱們這節課的HTML結構：web

<!DOCTYPE html>
<html lang="en" >
    <head>
        <meta charset="utf-8" />
        <meta name="author" content="Script Tutorials" />
        <title>WebGL With Three.js - Lesson 1 | Script Tutorials</title>
        <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
        <link href="css/main.css" rel="stylesheet" type="text/css" /> //本地樣式表
    </head>
    <body>
        <script src="http://cdnjs.cloudflare.com/ajax/libs/three.js/r69/three.min.js"></script>
        <script src="http://www.script-tutorials.com/demos/382/js/three.min.js"></script>
        <script src="http://www.script-tutorials.com/demos/382/js/OrbitControls.js"></script>
        <script src="http://www.script-tutorials.com/demos/382/js/stats.min.js"></script>
        <script src="js/script.js"></script> // 咱們待會要寫的內容
    </body>
</html>

在這段代碼中，咱們引入了全部今天要用到的庫。ajax

Javascript

我但願你已經見過咱們的demo和想象組成它的基本元素，咱們將一步一步解釋每一個部分的建立。segmentfault

主體

咱們的場景看起來像這樣：瀏覽器

var lesson1 = {
    scene: null,
    camera: null,
    renderer: null,
    container: null,
    controls: null,
    clock: null,
    stats: null,

    init: function() { // 初始化

    }
};

// 使場景動畫化
function animate() {
    requestAnimationFrame(animate);
    render();
    update();
}

// 更新控制器狀態
function update() {
    lesson1.controls.update(lesson1.clock.getDelta());
    lesson1.stats.update();
}

// 渲染場景
function render() {
    if (lesson1.renderer) {
        lesson1.renderer.render(lesson1.scene, lesson1.camera);
    }
}

// 在頁面加載時初始化 lesson 對象
function initializeLesson() {
    lesson1.init();
    animate();
}

if (window.addEventListener)
    window.addEventListener('load', initializeLesson, false);
else if (window.attachEvent)
    window.attachEvent('onload', initializeLesson);
else window.onload = initializeLesson;

這是用 three.js 建應用的經常使用結構。幾乎全部的東西都將在init方法裏建立。app

場景建立、相機和渲染

它們是咱們場景的主要元素，接下來的代碼將建立一個空場景，包含一個前景相機和可用的陰影映射渲染：框架

// 建立主要場景
this.scene = new THREE.Scene();

var SCREEN_WIDTH = window.innerWidth,
    SCREEN_HEIGHT = window.innerHeight;

// 準備相機
var VIEW_ANGLE = 45, ASPECT = SCREEN_WIDTH / SCREEN_HEIGHT, NEAR = 1, FAR = 10000;
this.camera = new THREE.PerspectiveCamera( VIEW_ANGLE, ASPECT, NEAR, FAR);
this.scene.add(this.camera);
this.camera.position.set(-1000, 1000, 0);
this.camera.lookAt(new THREE.Vector3(0,0,0));

// 準備渲染
this.renderer = new THREE.WebGLRenderer({antialias:true, alpha: false});
this.renderer.setSize(SCREEN_WIDTH, SCREEN_HEIGHT);
this.renderer.setClearColor(0xffffff);

this.renderer.shadowMapEnabled = true;
this.renderer.shadowMapSoft = true;

// 準備容器
this.container = document.createElement('div');
document.body.appendChild(this.container);
this.container.appendChild(this.renderer.domElement);

// 事件
THREEx.WindowResize(this.renderer, this.camera);

咱們將相機把相機放在45度角，設爲全屏幕大小，WebGLRenderer設爲白色，再把咱們的場景添加到HTML文檔中，並且在瀏覽器窗口大小變化時，用THREEx.WindowResize 來控制渲染和相機的變化。less

OrbitControls 和 Stats

爲了可以在某種程度上控制相機的 —— three.js 給咱們提供了現成的控件。其中之一是 OrbitControls，它能在場景中繞其軸線旋轉。一個小插件stats.min.js將有助於咱們看到場景的統計（FPS）。dom

// 準備控制器 (OrbitControls)
this.controls = new THREE.OrbitControls(this.camera, this.renderer.domElement);
this.controls.target = new THREE.Vector3(0, 0, 0);

// 準備計時器
this.clock = new THREE.Clock();

// 準備統計
this.stats = new Stats();
this.stats.domElement.style.position = 'absolute';
this.stats.domElement.style.bottom = '0px';
this.stats.domElement.style.zIndex = 10;
this.container.appendChild( this.stats.domElement );

所以，咱們準備好了四個元素。

光和場地的創做

光是一個場景中的重要元素，在咱們的第一個教程，咱們將建立最簡單的定向光線，由於咱們要添加基本的陰影：

// 添加定向光線
var dLight = new THREE.DirectionalLight(0xffffff);
dLight.position.set(1, 1000, 1);
dLight.castShadow = true;
dLight.shadowCameraVisible = true;
dLight.shadowDarkness = 0.2;
dLight.shadowMapWidth = dLight.shadowMapHeight = 1000;
this.scene.add(dLight);

// 添加粒子光線
particleLight = new THREE.Mesh( new THREE.SphereGeometry(10, 10, 10), new THREE.MeshBasicMaterial({ color: 0x44ff44 }));
particleLight.position = dLight.position;
this.scene.add(particleLight);

// 添加簡單的場地
var groundGeometry = new THREE.PlaneGeometry(1000, 1000, 1, 1);
ground = new THREE.Mesh(groundGeometry, new THREE.MeshLambertMaterial({
    color: this.getRandColor()
}));
ground.position.y = 0;
ground.rotation.x = - Math.PI / 2;
ground.receiveShadow = true;
this.scene.add(ground);

當咱們建立燈光時，用了兩個參數 castShadow 和 shadowCameraVisible。這將使咱們可以直觀地看到光在哪裏，理解構造的過程（和邊界）的陰影。
你也可能會注意到，在添加光後，咱們增長了一個球形物體——爲你準備的，以便直觀地知道咱們的定向光源在什麼位置。咱們用一個平面做爲地面去接收陰影——咱們設置的receiveShadow參數爲true。

顏色

咱們將在場景中添加額外的對象。我用一個方法來生成不一樣顏色的部件。這個方法將從顏色列表中隨機返回一個預約義的顏色。

var colors = [
    0xFF62B0,
    0x9A03FE,
    0x62D0FF,
    0x48FB0D,
    0xDFA800,
    0xC27E3A,
    0x990099,
    0x9669FE,
    0x23819C,
    0x01F33E,
    0xB6BA18,
    0xFF800D,
    0xB96F6F,
    0x4A9586
];

getRandColor: function() {
    return colors[Math.floor(Math.random() * colors.length)];
}

CircleGeometry 、 CubeGeometry、CylinderGeometry 和 ExtrudeGeometry

幾何對象是用必要的數據（點、頂點、面等）來描述三維模型。咱們將建立平面的圓、立方體和圓柱體。Extrude Geometry是用來製做從路徑凸出的形狀。咱們要作個凸出的三角形：

// 添加圓形
var circle = new THREE.Mesh(new THREE.CircleGeometry(70, 50), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
circle.rotation.x = - Math.PI / 2;
circle.rotation.y = - Math.PI / 3;
circle.rotation.z = Math.PI / 3;
circle.position.x = -300;
circle.position.y = 150;
circle.position.z = -300;
circle.castShadow = circle.receiveShadow = true;
this.scene.add(circle);

// 添加方塊
var cube = new THREE.Mesh(new THREE.CubeGeometry(100, 100, 100), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
cube.rotation.x = cube.rotation.z = Math.PI * 0.1;
cube.position.x = -300;
cube.position.y = 150;
cube.position.z = -100;
cube.castShadow = cube.receiveShadow = true;
this.scene.add(cube);

// 添加圓柱
var cube = new THREE.Mesh(new THREE.CylinderGeometry(60, 80, 90, 32), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
cube.rotation.x = cube.rotation.z = Math.PI * 0.1;
cube.position.x = -300;
cube.position.y = 150;
cube.position.z = 100;
cube.castShadow = cube.receiveShadow = true;
this.scene.add(cube);

// 添加不規則的物體
var extrudeSettings = {
    amount: 10,
    steps: 10,
    bevelSegments: 10,
    bevelSize: 10,
    bevelThickness: 10
};
var triangleShape = new THREE.Shape();
triangleShape.moveTo(  0, -50 );
triangleShape.lineTo(  -50, 50 );
triangleShape.lineTo( 50, 50 );
triangleShape.lineTo(  0, -50 );

var extrude = new THREE.Mesh(new THREE.ExtrudeGeometry(triangleShape, extrudeSettings), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
extrude.rotation.y = Math.PI / 2;
extrude.position.x = -300;
extrude.position.y = 150;
extrude.position.z = 300;
extrude.castShadow = extrude.receiveShadow = true;
this.scene.add(extrude);

幾何體建好後，咱們能夠建立一個在這個幾何的基礎上的網格。

IcosahedronGeometry 、 OctahedronGeometry 、 RingGeometry 和 ShapeGeometry

接下來咱們將建立四個元素：二十面體、八面體、環，和用shapegeometry對象自定義的路徑（形狀）：

// 二十面體
var icosahedron = new THREE.Mesh(new THREE.IcosahedronGeometry(70), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
icosahedron.position.x = -100;
icosahedron.position.y = 150;
icosahedron.position.z = -300;
icosahedron.castShadow = icosahedron.receiveShadow = true;
this.scene.add(icosahedron);

// 八面體
var octahedron = new THREE.Mesh(new THREE.OctahedronGeometry(70), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
octahedron.position.x = -100;
octahedron.position.y = 150;
octahedron.position.z = -100;
octahedron.castShadow = octahedron.receiveShadow = true;
this.scene.add(octahedron);

// 環
var ring = new THREE.Mesh(new THREE.RingGeometry(30, 70, 32), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
ring.rotation.y = -Math.PI / 2;
ring.position.x = -100;
ring.position.y = 150;
ring.position.z = 100;
ring.castShadow = ring.receiveShadow = true;
this.scene.add(ring);

// 幾何結構
var shapeG = new THREE.Mesh(new THREE.ShapeGeometry(triangleShape), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
shapeG.rotation.y = -Math.PI / 2;
shapeG.position.x = -100;
shapeG.position.y = 150;
shapeG.position.z = 300;
shapeG.castShadow = shapeG.receiveShadow = true;
this.scene.add(shapeG);

SphereGeometry 、 TetrahedronGeometry 、 TorusGeometry、 TorusKnotGeometry 和 TubeGeometry

最後，咱們建立一個球體、四面體、圓環、圓環管：

// 球體
var sphere = new THREE.Mesh(new THREE.SphereGeometry(70, 32, 32), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
sphere.rotation.y = -Math.PI / 2;
sphere.position.x = 100;
sphere.position.y = 150;
sphere.position.z = -300;
sphere.castShadow = sphere.receiveShadow = true;
this.scene.add(sphere);

// 四面體
var tetrahedron = new THREE.Mesh(new THREE.TetrahedronGeometry(70), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
tetrahedron.position.x = 100;
tetrahedron.position.y = 150;
tetrahedron.position.z = -100;
tetrahedron.castShadow = tetrahedron.receiveShadow = true;
this.scene.add(tetrahedron);

// 圓環
var torus = new THREE.Mesh(new THREE.TorusGeometry(70, 20, 16, 100), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
torus.rotation.y = -Math.PI / 2;
torus.position.x = 100;
torus.position.y = 150;
torus.position.z = 100;
torus.castShadow = torus.receiveShadow = true;
this.scene.add(torus);

// 圓環管
var torusK = new THREE.Mesh(new THREE.TorusKnotGeometry(70, 20, 16, 100), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
torusK.rotation.y = -Math.PI / 2;
torusK.position.x = 100;
torusK.position.y = 150;
torusK.position.z = 300;
torusK.castShadow = torusK.receiveShadow = true;
this.scene.add(torusK);

// 不規則的圓環結管
var points = [];
for (var i = 0; i < 10; i++) {
    var randomX = -100 + Math.round(Math.random() * 200);
    var randomY = -100 + Math.round(Math.random() * 200);
    var randomZ = -100 + Math.round(Math.random() * 200);

    points.push(new THREE.Vector3(randomX, randomY, randomZ));
}
var tube = new THREE.Mesh(new THREE.TubeGeometry(new THREE.SplineCurve3(points), 64, 20), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
tube.rotation.y = -Math.PI / 2;
tube.position.x = 0;
tube.position.y = 500;
tube.position.z = 0;
tube.castShadow = tube.receiveShadow = true;
this.scene.add(tube);

注意構造管過程，TubeGeometry 容許咱們經過一組點創建一個圓柱形物體。

光的平滑運動

爲了順利地將光，咱們只須要在update方法裏添加如下代碼：

var timer = Date.now() * 0.000025;
particleLight.position.x = Math.sin(timer * 5) * 300;
particleLight.position.z = Math.cos(timer * 5) * 300;

未完待續~

原文 WebGL With Three.js – Lesson 1
由 SegmentFault 編譯

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