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今天就跟大家聊聊有關(guān)使用Cesium實(shí)現(xiàn)繪制一個(gè)拋物弧線,可能很多人都不太了解,為了讓大家更加了解,小編給大家總結(jié)了以下內(nèi)容,希望大家根據(jù)這篇文章可以有所收獲。
思路
兩點(diǎn)連線作為坐標(biāo)軸,模擬拋物線,在線上取點(diǎn)畫直線,主要用于高度/p>
取n個(gè)點(diǎn),依次畫線,得到近似的拋物線,點(diǎn)越多越光滑
JS代碼
// 兩點(diǎn)之間拋物線繪制函數(shù),twoPoints是一個(gè)數(shù)組:[lon1,lat1,lon2,lat2] function animatedParabola(twoPoints) { //動(dòng)態(tài)拋物線繪制 let startPoint = [twoPoints[0],twoPoints[1],0]; //起點(diǎn)的經(jīng)度、緯度 let end = [twoPoints[2],twoPoints[3]]; //終點(diǎn)的經(jīng)度、緯度 let step = 80; //線的數(shù)量,越多則越平滑 let heightProportion = 0.125; //最高點(diǎn)和總距離的比值(即圖中H比上AB的值) let dLon = (end[0] - startPoint[0])/step; //經(jīng)度差值 let dLat = (end[1] - startPoint[1])/step; //緯度差值 let deltaLon = dLon * Math.abs(111000*Math.cos(twoPoints[1])); //經(jīng)度差(米級(jí)) let deltaLat = dLat * 111000; //緯度差(米),1緯度相差約111000米 let endPoint = [0,0,0]; //定義一個(gè)端點(diǎn)(后面將進(jìn)行startPoint和endPoint兩點(diǎn)畫線) let heigh = (step * Math.sqrt(deltaLon*deltaLon+deltaLat*deltaLat) * heightProportion).toFixed(0); let x2 = (10000*Math.sqrt(dLon*dLon+dLat*dLat)).toFixed(0); //小數(shù)點(diǎn)擴(kuò)大10000倍,提高精確度 let a = (heigh/(x2*x2)); //拋物線函數(shù)中的a function y(x,height) { //模擬拋物線函數(shù)求高度 //此處模擬的函數(shù)為y = H - a*x^2 (H為高度常數(shù)) return height - a*x*x; } for(let i = 1;i <= step; i++){ //逐“幀”畫線 endPoint[0] = startPoint[0] + dLon; //更新end點(diǎn)經(jīng)度 endPoint[1] = startPoint[1] + dLat; //更新end點(diǎn)緯度 let x = x2*(2*i/step-1); //求拋物線函數(shù)x endPoint[2] = (y(x,heigh)).toFixed(0); //求end點(diǎn)高度 viewer.clock.currentTime = Cesium.JulianDate.now(); //將時(shí)鐘指針移到當(dāng)前時(shí)間 //這里viewer是容器初始化時(shí)new Cesium.Viewer構(gòu)造的: var viewer = new Cesium.Viewer('mapContainer', {...}); let IsoTime = Cesium.JulianDate.now(); //獲取當(dāng)前時(shí)間 viewer.entities.add({ //添加動(dòng)態(tài)線 polyline: { positions: Cesium.Cartesian3.fromDegreesArrayHeights(startPoint.concat(endPoint)), width: 4, material: new Cesium.PolylineOutlineMaterialProperty({ color: Cesium.Color.GOLD, outlineWidth: 0.3, }) }, availability: new Cesium.TimeIntervalCollection([new Cesium.TimeInterval({ //設(shè)置顯示的時(shí)間區(qū)間 start: { dayNumber: IsoTime.dayNumber, secondsOfDay: IsoTime.secondsOfDay+((i-1)*300), }, stop: { dayNumber: IsoTime.dayNumber, secondsOfDay: IsoTime.secondsOfDay+(i*300), }, })]), }); viewer.entities.add({ //添加靜態(tài)線 polyline: { positions: Cesium.Cartesian3.fromDegreesArrayHeights(startPoint.concat(endPoint)), width: 4, material: new Cesium.PolylineGlowMaterialProperty({ color: Cesium.Color.AQUA.withAlpha(0.9), outlineWidth: 0.3, glowPower : 0.3, }) }, }); // end點(diǎn)變?yōu)閟tart點(diǎn) startPoint[0] = endPoint[0]; startPoint[1] = endPoint[1]; startPoint[2] = endPoint[2]; } viewer.clock.shouldAnimate = true; //啟動(dòng)時(shí)鐘開始轉(zhuǎn)動(dòng) viewer.clock.multiplier = 1600; //時(shí)鐘轉(zhuǎn)動(dòng)速度 }
function parabola(twoPoints) { //拋物線繪制 let startPoint = [twoPoints[0],twoPoints[1],0]; //起點(diǎn)的經(jīng)度、緯度 let end = [twoPoints[2],twoPoints[3]]; //終點(diǎn)的經(jīng)度、緯度 let step = 80; //線的多少,越多則越平滑(但過多瀏覽器緩存也會(huì)占用越多) let heightProportion = 0.125; //最高點(diǎn)和總距離的比值 let dLon = (end[0] - startPoint[0])/step; //經(jīng)度差值 let dLat = (end[1] - startPoint[1])/step; //緯度差值 let deltaLon = dLon * Math.abs(111000*Math.cos(twoPoints[1])); //經(jīng)度差(米級(jí)) let deltaLat = dLat * 111000; //緯度差(米),1緯度相差約111000米 let endPoint = [0,0,0]; //定義一個(gè)端點(diǎn)(后面將進(jìn)行startPoint和endPoint兩點(diǎn)畫線) let heigh = (step * Math.sqrt(deltaLon*deltaLon+deltaLat*deltaLat) * heightProportion).toFixed(0); let x2 = (10000*Math.sqrt(dLon*dLon+dLat*dLat)).toFixed(0); //小數(shù)點(diǎn)擴(kuò)大10000倍,提高精確度 let a = (heigh/(x2*x2)); function y(x,height) { return height - a*x*x; } for(var i = 1;i <= step; i++){ //逐“幀”畫線 endPoint[0] = startPoint[0] + dLon; //更新end點(diǎn)經(jīng)度 endPoint[1] = startPoint[1] + dLat; //更新end點(diǎn)緯度 let x = x2*(2*i/step-1); //求拋物線函數(shù)x endPoint[2] = (y(x,heigh)).toFixed(0); //求end點(diǎn)高度 viewer.entities.add({ //添加靜態(tài)線 polyline: { positions: Cesium.Cartesian3.fromDegreesArrayHeights(startPoint.concat(endPoint)), width: 4, material: new Cesium.PolylineGlowMaterialProperty({ color: Cesium.Color.AQUA.withAlpha(0.9), outlineWidth: 0.3, glowPower : 0.3, }) }, }); // end點(diǎn)變?yōu)閟tart點(diǎn) startPoint[0] = endPoint[0]; startPoint[1] = endPoint[1]; startPoint[2] = endPoint[2]; } }
示例
// An Example var viewer = new Cesium.Viewer('mapContainer'); var twoPoints = [114.3698, 22.6139, 114.2135, 22.6127]; animatedParabola(twoPoints);
運(yùn)行可得到:
看完上述內(nèi)容,你們對(duì)使用Cesium實(shí)現(xiàn)繪制一個(gè)拋物弧線有進(jìn)一步的了解嗎?如果還想了解更多知識(shí)或者相關(guān)內(nèi)容,請(qǐng)關(guān)注億速云行業(yè)資訊頻道,感謝大家的支持。
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