three.js(四)：react + three.js

绘制多个立方体

1.搭建react+ts 项目

npx create-react-app basics-demo --template typescript

react+ts 的用法可参考此链接： https://react-typescript-cheatsheet.netlify.app/docs/basic/setup

2.安装three依赖

npm install three @types/three --save

3.安装路由

npm install react-router@6 react-router-dom@6

react-router-v6 的用法可参考此链接：https://juejin.cn/post/7088526716049555492

4.用路由组件包裹APP。

index.tsx

import { BrowserRouter } from "react-router-dom";
import { createRoot } from "react-dom/client";
import App from "./App";const container = document.getElementById("root") as HTMLElement;
const root = createRoot(container);
root.render(<BrowserRouter><App /></BrowserRouter>
);

5.构建项目页面

src/view/Basics.tsx

import React from "react";const Basics: React.FC = (): JSX.Element => {return (<nav style={{ width: "60%", margin: "auto" }}><h2>three.js 基础示例</h2></nav>);
};export default Basics;

src/view/RenderStructure.tsx

import React from "react";const RenderStructure: React.FC = (): JSX.Element => {return <div>RenderStructure 渲染结构</div>;
};export default RenderStructure;

6.用useRoutes hook 搭建路由。

App.tsx

import React from "react";
import { useRoutes } from "react-router-dom";
import "./App.css";
import Basics from "./view/Basics";
import RenderStructure from "./view/RenderStructure";const App: React.FC = (): JSX.Element => {const routing = useRoutes([{path: "/",element: <Basics />,},{path: "RenderStructure",element: <RenderStructure />,]);return <>{routing}</>;
};export default App;

7.建立导航栏

src/view/Basics.tsx

import React from "react";
import { Link } from "react-router-dom";const Basics: React.FC = (): JSX.Element => {return (<nav style={{ width: "60%", margin: "auto" }}><h2>three.js 基础示例</h2><ul><li><Link to="/RenderStructure">RenderStructure 渲染结构</Link></li></ul></nav>);
};
export default Basics;

8.在RenderStructure.tsx 页面导入立方体

src/view/RenderStructure.tsx

import React, { useRef, useEffect } from "react";
import { BoxGeometry, DirectionalLight, Mesh, MeshNormalMaterial, MeshPhongMaterial, PerspectiveCamera, Scene, WebGLRenderer } from "three";const { innerWidth, innerHeight } = window;const scene = new Scene();
const camera = new PerspectiveCamera(75, innerWidth / innerHeight, 0.1, 1000);
camera.position.z = 5;const renderer = new WebGLRenderer();
renderer.setSize(innerWidth, innerHeight);const geometry = new BoxGeometry();
const material = new MeshNormalMaterial();
const cube = new Mesh(geometry, material);
scene.add(cube);function animate() {requestAnimationFrame(animate);cube.rotation.x += 0.01;cube.rotation.y += 0.01;renderer.render(scene, camera);
}const RenderStructure: React.FC = (): JSX.Element => {const divRef = useRef<HTMLDivElement>(null);useEffect(() => {const { current } = divRef;if (current) {current.innerHTML = "";current.append(renderer.domElement);animate();}}, []);return <div ref={divRef}></div>;
};export default RenderStructure;

在上面的代码中，没有直接建立，而是在WebGLRenderer 对象的实例化方法里建立的，在其源码可以找到相关逻辑：

function WebGLRenderer( parameters = {} ) {const _canvas = parameters.canvas !== undefined ? parameters.canvas : createCanvasElement()……this.domElement = _canvas;……
}

通过WebGLRenderer 对象建立了canvas后，再在react的函数组件的useEffect hook 中，将canvas 添加到div 中。

const RenderStructure: React.FC = (): JSX.Element => {const divRef = useRef<HTMLDivElement>(null);useEffect(() => {const { current } = divRef;current && current.append(renderer.domElement);animate();}, []);return <div ref={divRef}></div>;
};

当前这个立方体的材质是MeshNormalMaterial，并不受光照影响

9.给立方体换个MeshPhongMaterial 材质，再添加光源

const geometry = new BoxGeometry();
const material = new MeshPhongMaterial({ color: 0x44aa88 });
const cube = new Mesh(geometry, material);
scene.add(cube);const color = 0xffffff;
const intensity = 1;
const light = new DirectionalLight(color, intensity);
light.position.set(-1, 2, 4);
scene.add(light);

当前的渲染结构如下：
效果如下：

10. 添加两个立方体，几何体和材质可被多个Mesh 对象共享

const geometry = new BoxGeometry();
const material = new MeshPhongMaterial({ color: 0x44aa88 });const cubes = [-2, 0, 2].map((num) => makeInstance(num));
scene.add(...cubes);function makeInstance(x: number) {const cube = new Mesh(geometry, material);cube.position.x = x;return cube;
}function animate() {requestAnimationFrame(animate);cubes.forEach((cube) => {cube.rotation.x += 0.01;cube.rotation.y += 0.01;});renderer.render(scene, camera);
}