06-ArcGIS For JavaScript-requestAnimationFrame动画渲染

文章目录

- 概述
- setInterval（）与setTimeout()
- requestAnimationFrame()
- requestAnimationFrame在ArcGIS For JavaScript的应用
- 结果

概述

本节主要讲解与时间相关的三个方法setTimeout()、setInterval()和requestAnimationFrame()，这三个方法都属于浏览器的window对象的方法，这三个函数能够更好的服务于2Dcanvas动画、WebGL动画等方面。

setInterval（）与setTimeout()

setInterval()函数为周期定时器，可以选择每过一个固定时间段调用一次指定函数。如下，每100毫秒调用一次回调函数：

setInterval(function(){console.log("It is setInterval");
}, 100);

setTimeout()为倒计时定时器，例如可以指定100毫秒后调用回调函数，然后结束当前定时。

setTimeout(function(){console.log("It is setTimeout");
}, 100);

这两个方法都是可以人为的指定回调函数被调用的时间。
如果不想使用该定时器的时候，可以选择取消。方法如下：

clearInterval();  //取消setInterval()设置的定时
clearTimeout();  //取消setTimeout()设置的定时器

requestAnimationFrame()

requestAnimationFrame主要用途是按帧对网页进行重绘，让各种网页动画效果（DOM动画、Canvas动画、SVG动画、WebGL动画）能够有一个统一的刷新机制，从而节省系统资源，提高系统性能，改善视觉效果。

调用方式如下：

function callback(){console.log(requestAnimationFrame)requestAnimationFrame(callback)
}
requestAnimationFrame(callback)

requestAnimationFrame在ArcGIS For JavaScript的应用

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title><link rel="stylesheet" href="https://js.arcgis.com/4.30/esri/themes/light/main.css" /><script src="https://js.arcgis.com/4.30/"></script><style>html,body,#viewDiv {margin: 0;padding: 0;height: 100%;width: 100%;}</style><script>require(["esri/geometry/Mesh","esri/views/SceneView","esri/Map","esri/Graphic","esri/symbols/MeshSymbol3D","esri/symbols/FillSymbol3DLayer","esri/geometry/Point","esri/core/reactiveUtils"], (Mesh, SceneView, Map, Graphic, MeshSymbol3D, FillSymbol3DLayer, Point, reactiveUtils) => {let waterHeight = 422;async function createMeshGLTF(glbUrl, point, i = [0, 0, 0], r = 1, n = 0) {const s = await Mesh.createFromGLTF(point, glbUrl, {vertexSpace: "georeferenced"}), o = i.map(h => h * r);return s.scale(r),s.offset(o[0], o[1], o[2]),s.rotate(0, 0, n),new Graphic({geometry: s,symbol: new MeshSymbol3D({symbolLayers: [new FillSymbol3DLayer]})})}let map = new Map({basemap: 'satellite'})let view = new SceneView({container: "viewDiv",map})let animatingPinpoint = true;view.when(async function () {let sailBoat = await createMeshGLTF("./pinpoint.glb", new Point({x: -1354454634895185e-8,y: 4307521548889681e-9,z: waterHeight,spatialReference: {wkid: 102100}}));view.graphics.add(sailBoat);view.extent = sailBoat.geometry.extent;function setupCameraHeadingListener() {reactiveUtils.watch(() => Math.round(view.camera.heading), e => {const i = sailBoat.geometry;i.transform.rotationAngle = -e + 20,i.transform.rotationAxis = [0, 0, 1]}, {initial: !0})}let startTime = Date.now() / 1000;function animatePinpoint(graphic) {let startTime = null;animatingPinpoint = true;const animate = (elapsedTime) => {if (!startTime) {startTime = elapsedTime;}const timeDif = (elapsedTime - startTime) / 1000;const scale = 1 + Math.abs(Math.sin(timeDif * 2));const geometry = graphic.geometry;geometry.transform ??= new MeshTransform();geometry.transform.scale = [scale, scale, scale];if (animatingPinpoint) {requestAnimationFrame(animate);}}requestAnimationFrame(animate);}function stopAnimatingPinpoint() {animatingPinpoint = false;}animatePinpoint(sailBoat);setupCameraHeadingListener();})})</script>
</head><body><div id="viewDiv"></div>
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