CesiumJS整合ThreeJS插件封装

最近做项目有一个三维需求使用CesiumJS比较难以实现，发现THREEJS中效果比较合适，于是准备将THREEJS整合到CesiumJS中

为实现效果所需我们找到官方Integrating Cesium with Three.js博客，于是根据该博客提供的思路去实现整合

文章目录

- 一、创建ThreeJS类
- 二、插件threeJs 优化
- - 1、创建ThressScene工具
  - - 1.1、同步camera
    - 1.2、同步场景中的物体
    - 1.3、同步render
  - 2、插件使用
  - - 2.1 引入插件初始化map
    - 2.1 初始化Meshes
    - 2.2 初始化threeScene
    - 2.3 效果预览

一、创建ThreeJS类

为了开发时更好的扩展性把他写到了一个ThreeJS 类里面，功能直接调用即可

function ThreeJs(viewer, cesiumGlobal, defaultStatic, threeConf) {
  if (viewer && threeConf) {
    const { threeGlobal, containerId, threeContainerId } = threeConf;
    Cesium = cesiumGlobal;
    THREE = threeGlobal;
    this._viewer = viewer;
    this._containerId = containerId;
    this._threeContainerId = threeContainerId;
    this._initContainer();
    this._initThree();
  }
}
//部分省略......

项目中使用

import { ThreeJs } from 'cesium_dev_kit'

// 初始化map
 initMap (){
     const ThreeJsObj = new ThreeJs({
        cesiumGlobal: Cesium,
        threeGlobal: THREE,
        containerId: 'cesiumContainer',
        threeContainerId: 'threeContainer',
//部分省略......
      })
      this.c_viewer = ThreeJsObj.viewer;
      this.threeJs = ThreeJsObj.threeJs;
      this.initThree(this.threeJs);
  },
  // 初始化ThreeJs
 initThree (ThreeJs) {
      const threeDObject = this.create3DOject(ThreeJs, this.c_viewer);
      ThreeJs.addThreeObjects(threeDObject)

      this.c_viewer.camera.lookAtTransform(Cesium.Matrix4.IDENTITY)//解除视角锁定
    },
    // 创建三维模型
  create3DOject (threeObj, viewer) {
      let three = threeObj._three;
      let _3Dobjects = [], _3DOB;
      let entity = {
        name: 'Polygon',
        polygon: {
          hierarchy: Cesium.Cartesian3.fromDegreesArray([
            minWGS84[0], minWGS84[1],
            maxWGS84[0], minWGS84[1],
            maxWGS84[0], maxWGS84[1],
            minWGS84[0], maxWGS84[1]
          ]),
          material: Cesium.Color.RED.withAlpha(0.1)
        }
      }
      let Polypon = viewer.entities.add(entity);
      let doubleSideMaterial = new THREE.MeshNormalMaterial({
        side: THREE.DoubleSide
      });
//部分省略......
      return _3Dobjects;
    }

根据官网的思量整合后最终实现效果如下

效果是实现了，但是这个封装耦合性相当高，多个功能都需要使用这个插件时特别蹩脚，于是开始了下一次造…

二、插件threeJs 优化

理解官方案例的思路整合关键主要有三个方面，第一个是同步Camera，第二个是同步Scene中的物体位置，第三个是需要同步CesiumJS和THREEJS 的render重绘程序

1、创建ThressScene工具

为了扩展与管理我们抽离一个Scene 的工具js

class Scene extends THREE.Scene {}

在这个js 里面去实现插件操作的优化

1.1、同步camera

创建一个updateCameraMatrix来同步项目位置，核心代码如下

  updateCameraMatrix() {
      //同步相机
      this.camera.fov = Cesium.Math.toDegrees(
        this.cesiumViewer.camera.frustum.fovy
      ) // ThreeJS FOV is vertical
      this.camera.updateProjectionMatrix()

      this.camera.matrixAutoUpdate = false
      const cvm = this.cesiumViewer.camera.viewMatrix
      const civm = this.cesiumViewer.camera.inverseViewMatrix
      this.camera.lookAt(this.cameraCenter)
//部分省略......
      const width = this.cesiumViewer.scene.canvas.clientWidth
      const height = this.cesiumViewer.scene.canvas.clientHeight
      this.camera.aspect = width / height
      this.camera.updateProjectionMatrix()

      this.renderer.setSize(width, height)

      return this
    }

1.2、同步场景中的物体

创建一个updateGroupMatrixWorld来进行物体位置同步，核心代码如下

	 // 重写add 方法
     add(object) {
      if (arguments.length > 1) {
        for (let i = 0; i < arguments.length; i++) {
          this.childrenGroup.add(arguments[i])
        }

        return this
      }
	//部分省略......
      return this
    }
    updateGroupMatrixWorld() {
      // 得到面向模型的前向方向
      const center = this.cartesian3ToVector(
        Cesium.Cartesian3.fromDegrees(this.lngLat[0], this.lngLat[1], 0)
      )
      // 使用从左下到左上的方向作为上向量
      const topLeft = this.cartesian3ToVector(
        Cesium.Cartesian3.fromDegrees(this.lngLat[0], this.lngLat[1], 2)
      )
      const latDir = new THREE.Vector3().subVectors(center, topLeft).normalize()

      // 配置实体的位置和方向
      // this.syncGroup.position.copy(center)
      this.syncGroup.lookAt(latDir)
      this.syncGroup.up.copy(latDir)
      this.syncGroup.updateMatrix()

      this.cameraOffset.copy(center)

      this.sphere.position.set(0 - center.x, 0 - center.y, 0 - center.z)
      this.syncGroup.up.set(0, 0, -1)
      this.up.set(0, 0, -1)

      return this
    }

1.3、同步render

    renderCesium() {
      this.cesiumViewer.render()
      return this
    }

    renderThree() {
      this.renderer.render(this, this.camera)
      return this
    }
    
   loop(callback) {
    const _loop = function () {
      let time = requestAnimationFrame(_loop)
      callback && callback(time)
    }
    _loop()
  }

2、插件使用

插件改完了心里还是有点鸡冻，马上在项目中引入开始测试

2.1 引入插件初始化map

import { initCesium } from 'cesium_dev_kit'

// 初始化map
 initMap (){
      const { viewer, threeJs, base, graphics, material } = new initCesium({
        cesiumGlobal: Cesium,
        threeGlobal: THREE,
        containerId: 'cesiumContainer',
        threeContainerId: 'threeContainer',
		//部分省略......
      })
      this.c_viewer = viewer;
      this.threeJs = threeJs;
      this.base = base;
      this.graphics = graphics;
      this.material = material
      this.initThree(this.threeJs);
      // this.getClickPosition()
      this.createAEllipsoid();
      this.createAFanShape();
  },

2.1 初始化Meshes

这里我们就使用官方的extrude案例

    initMeshes (scene) {
      // 环形 extrude
      const closedSpline = new THREE.CatmullRomCurve3([
        new THREE.Vector3(-60, 30, 60), // 左下
        new THREE.Vector3(-60, 100, 60), // 左中
        new THREE.Vector3(-60, 220, 60), // 左上
        new THREE.Vector3(60, 80, -60), // 右中
        new THREE.Vector3(60, 30, -60), // 右下
      ]);
      // 2、extrude settings
      closedSpline.curveType = "catmullrom";
      closedSpline.closed = true;
      const extrudeSettings = {
        steps: 100,
        bevelEnabled: false,
        extrudePath: closedSpline,
      };
      // 3、construct shape
      const r = 20; // 截面半径
      const pts1 = [];
      const count = 3; // 截面的棱边数量
      for (let index = 0; index < count; index++) {
        // index/count 几分之几，2π为周长
        const a = (index / count) * Math.PI * 2;
        pts1.push(new THREE.Vector2(r * Math.cos(a), r * Math.sin(a)));
      }
      const shape1 = new THREE.Shape(pts1);
      // create geometry
      const geometry1 = new THREE.ExtrudeGeometry(shape1, extrudeSettings);
      // create material
      const material1 = new THREE.MeshLambertMaterial({
        color: 0xb00000,
      });
      // assembly meshes
      const mesh1 = new THREE.Mesh(geometry1, material1);
      // add mesh to scene
      scene.add(mesh1);
		//部分省略......
    },

2.2 初始化threeScene

    initThree (ThreeJs) {
      const { scene, camera } = ThreeJs.initThree({ center, axesHelper: true, threeHabit: false });
      this.initLight(scene, camera)
      this.initMeshes(scene);
      this.flyto(scene);
      ThreeJs.loop(function () {
        scene.update();
      })
    },