three.js and cesium

转载已于 2025-02-11 15:30:50 修改 · 3.5k 阅读

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原文链接：https://zhuanlan.zhihu.com/page/9685742340760829

文章标签：

#threejs #cesium #cesiumjs #gis #数字地球

于 2019-06-17 15:18:21 首次发布

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本文介绍了将Cesium的行星级渲染和GIS功能与Three.js通用3D API相结合的方法。两者都是用于3D可视化的JavaScript库，有相似之处。文中给出了整合步骤，包括初始化渲染器、3D对象和循环渲染器，并提供了详细的代码示例。

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Three.js是一个轻量级的跨浏览器JavaScript库，用于在浏览器中创建和显示动画3D计算机图形。将Cesium的行星级渲染和GIS功能与Three.js广泛而易用的通用3D API相结合，为新的WebGL体验开启了许多可能性。3D JavaScript库现在已经完全成熟并且广为人知，使得开发人员可以避免在浏览器中使用3D的麻烦。开发人员可以轻松创建相机，对象，灯光，材质和图形，并选择渲染器，使用HTML 5的画布，WebGL或SVG绘制场景。

因为Cesium和Three.js都是用于3D可视化的，并且是从头开始用JavaScript构建的，所以它们有相似之处，可以将这些惊人的库集成在一起。我对这两个框架进行整合的方法比看起来简单：我将这两个框架分离到了不同的视图中，并参考了HTML Canvas元素，并将它们的控制器组合在同一个坐标系中。由于两者都是开源的，我可以分享这个演示，这将涵盖一些基础知识。

上：Cesium场景。中：Three.js场景。下：组合的场景。

Cesiumjs是一个为了创建数字地球而开发的三维图书馆，其渲染对于真实的地球来说是非常精确的。借助3D Tiles，开发人员可以将几乎所有内容都重新渲染到浏览器中的数字画布上。

指导Cesium的基本渲染原理与Three.js没有太大区别。Three.js是用于渲染3D对象的强大3D库。通过在两个场景中复制铯的球面坐标系和匹配的数字地球，很容易将两个单独的渲染引擎层整合到一个主场景中。我将给出一个关于其整合方法的简单说明，如下所示：

初始化Cesium渲染器，
初始化Three.js渲染器，
初始化这两个库的3D对象，和
循环渲染器。

<!DOCTYPE html>
<html lang="en">
<head>

<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=Edge,chrome=1">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=no">
<title>Tools-12CesiumThreejs</title>
<link href="Tools-12CesiumThreejs.css" rel="stylesheet" type="text/css" media="all">
<script src="../Cesium/Cesium.js"></script>
<script src="Libs/Three/three.js"></script>
</head>
<body onload="pageload()">
<div id="cesiumContainer"></div>
<div id="ThreeContainer"></div>
<div id="cover">
<div id="loadingIndicator" class="loadingIndicator"></div>
</div>
<script>
function pageload() {
var loadingIndicator = document.getElementById('loadingIndicator');
loadingIndicator.style.display = 'none';
// boundaries in WGS84 around the object
var minWGS84 = [115.23, 39.55];
var maxWGS84 = [116.23, 41.55];
var cesiumContainer = document.getElementById("cesiumContainer");
var ThreeContainer = document.getElementById("ThreeContainer");
var _3Dobjects = []; //Could be any Three.js object mesh
var three = {
renderer: null,
camera: null,
scene: null
};
var cesium = {
viewer: null
};
function _3DObject() {
//THREEJS 3DObject.mesh
this.threeMesh = null;
//location bounding box
this.minWGS84 = null;
this.maxWGS84 = null;
}
function initCesium() {
cesium.viewer = new Cesium.Viewer(cesiumContainer, {
useDefaultRenderLoop: false,
selectionIndicator: false,
homeButton: false,
sceneModePicker: false,
navigationHelpButton: false,
infoBox: false,
navigationHelpButton: false,
navigationInstructionsInitiallyVisible: false,
animation: false,
timeline: false,
fullscreenButton: false,
allowTextureFilterAnisotropic: false,
contextOptions: {
webgl: {
alpha: false,
antialias: true,
preserveDrawingBuffer: true,
failIfMajorPerformanceCaveat: false,
depth: true,
stencil: false,
anialias: false
},
},
targetFrameRate: 60,
resolutionScale: 0.1,
orderIndependentTranslucency: true,
//imageryProvider: undefined,
baseLayerPicker: true,
geocoder: false,
automaticallyTrackDataSourceClocks: false,
dataSources: null,
clock: null,
terrainShadows: Cesium.ShadowMode.DISABLED
});
var center = Cesium.Cartesian3.fromDegrees(
(minWGS84[0] + maxWGS84[0]) / 2,
((minWGS84[1] + maxWGS84[1]) / 2) - 1,
200000
);
cesium.viewer.camera.flyTo({
destination: center,
orientation: {
heading: Cesium.Math.toRadians(0),
pitch: Cesium.Math.toRadians(-60),
roll: Cesium.Math.toRadians(0)
},
duration: 3
});
}
function initThree() {
var fov = 45;
var width = window.innerWidth;
var height = window.innerHeight;
var aspect = width / height;
var near = 1;
var far = 10 * 1000 * 1000;
three.scene = new THREE.Scene();
three.camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
three.renderer = new THREE.WebGLRenderer({ alpha: true });
ThreeContainer.appendChild(three.renderer.domElement);
}
function init3DObject() {
//Cesium entity
var 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(0.2)
}
};
var Polygon = cesium.viewer.entities.add(entity);
//Three.js Objects
// Lathe geometry
var doubleSideMaterial = new THREE.MeshNormalMaterial({
side: THREE.DoubleSide
});
var segments = 10;
var points = [];
for (var i = 0; i < segments; i++) {
points.push(new THREE.Vector2(Math.sin(i * 0.2) * segments + 5, (i - 5) * 2));
}
var geometry = new THREE.LatheGeometry(points);
var latheMesh = new THREE.Mesh(geometry, doubleSideMaterial);
latheMesh.scale.set(1500, 1500, 1500); //scale object to be visible at planet scale
latheMesh.position.z += 15000.0; // translate "up" in Three.js space so the "bottom" of the mesh is the handle
latheMesh.rotation.x = Math.PI / 2; // rotate mesh for Cesium's Y-up system
var latheMeshYup = new THREE.Group();
latheMeshYup.add(latheMesh)
three.scene.add(latheMeshYup); // don’t forget to add it to the Three.js scene manually
//Assign Three.js object mesh to our object array
var _3DOB = new _3DObject();
_3DOB.threeMesh = latheMeshYup;
_3DOB.minWGS84 = minWGS84;
_3DOB.maxWGS84 = maxWGS84;
_3Dobjects.push(_3DOB);
// dodecahedron
geometry = new THREE.DodecahedronGeometry();
var dodecahedronMesh = new THREE.Mesh(geometry, new THREE.MeshNormalMaterial());
dodecahedronMesh.scale.set(5000, 5000, 5000); //scale object to be visible at planet scale
dodecahedronMesh.position.z += 15000.0; // translate "up" in Three.js space so the "bottom" of the mesh is the handle
dodecahedronMesh.rotation.x = Math.PI / 2; // rotate mesh for Cesium's Y-up system
var dodecahedronMeshYup = new THREE.Group();
dodecahedronMeshYup.add(dodecahedronMesh)
three.scene.add(dodecahedronMeshYup); // don’t forget to add it to the Three.js scene manually
//Assign Three.js object mesh to our object array
_3DOB = new _3DObject();
_3DOB.threeMesh = dodecahedronMeshYup;
_3DOB.minWGS84 = minWGS84;
_3DOB.maxWGS84 = maxWGS84;
_3Dobjects.push(_3DOB);
}
// Looping Renderer
function renderCesium() {
cesium.viewer.render();
}
function renderThreeObj() {
// register Three.js scene with Cesium
three.camera.fov = Cesium.Math.toDegrees(cesium.viewer.camera.frustum.fovy) // ThreeJS FOV is vertical
three.camera.updateProjectionMatrix();
var cartToVec = function (cart) {
return new THREE.Vector3(cart.x, cart.y, cart.z);
};
// Configure Three.js meshes to stand against globe center position up direction
for (var id in _3Dobjects) {
minWGS84 = _3Dobjects[id].minWGS84;
maxWGS84 = _3Dobjects[id].maxWGS84;
// convert lat/long center position to Cartesian3
var center = Cesium.Cartesian3.fromDegrees((minWGS84[0] + maxWGS84[0]) / 2, (minWGS84[1] + maxWGS84[1]) / 2);
// get forward direction for orienting model
var centerHigh = Cesium.Cartesian3.fromDegrees((minWGS84[0] + maxWGS84[0]) / 2, (minWGS84[1] + maxWGS84[1]) / 2, 1);
// use direction from bottom left to top left as up-vector
var bottomLeft = cartToVec(Cesium.Cartesian3.fromDegrees(minWGS84[0], minWGS84[1]));
var topLeft = cartToVec(Cesium.Cartesian3.fromDegrees(minWGS84[0], maxWGS84[1]));
var latDir = new THREE.Vector3().subVectors(bottomLeft, topLeft).normalize();
// configure entity position and orientation
_3Dobjects[id].threeMesh.position.copy(center);
_3Dobjects[id].threeMesh.lookAt(centerHigh);
_3Dobjects[id].threeMesh.up.copy(latDir);
}
// Clone Cesium Camera projection position so the
// Three.js Object will appear to be at the same place as above the Cesium Globe
three.camera.matrixAutoUpdate = false;
var cvm = cesium.viewer.camera.viewMatrix;
var civm = cesium.viewer.camera.inverseViewMatrix;
three.camera.matrixWorld.set(
civm[0], civm[4], civm[8], civm[12],
civm[1], civm[5], civm[9], civm[13],
civm[2], civm[6], civm[10], civm[14],
civm[3], civm[7], civm[11], civm[15]
);
three.camera.matrixWorldInverse.set(
cvm[0], cvm[4], cvm[8], cvm[12],
cvm[1], cvm[5], cvm[9], cvm[13],
cvm[2], cvm[6], cvm[10], cvm[14],
cvm[3], cvm[7], cvm[11], cvm[15]
);
three.camera.lookAt(new THREE.Vector3(0, 0, 0));
var width = ThreeContainer.clientWidth;
var height = ThreeContainer.clientHeight;
var aspect = width / height;
three.camera.aspect = aspect;
three.camera.updateProjectionMatrix();
three.renderer.setSize(width, height);
three.renderer.render(three.scene, three.camera);
}
function loop() {
requestAnimationFrame(loop);
renderCesium();
renderThreeObj();
}
initCesium(); // Initialize Cesium renderer
initThree(); // Initialize Three.js renderer
init3DObject(); // Initialize Three.js object mesh with Cesium Cartesian coordinate system
loop(); // Looping renderer
}
</script>
</body>
</html>