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);
}

• 当前的渲染结构如下：
  
• 效果如下：