默认情况下,铯多义线遵循地球曲率,在两点之间。如何制作高于地面的弧线,就像在这个例子中一样?
答案 0 :(得分:5)
这是一个在实体位置上使用插值算法来计算平滑弧的示例。尝试点击"运行代码段"在底部,或load this in Sandcastle。
var viewer = new Cesium.Viewer('cesiumContainer', {
navigationInstructionsInitiallyVisible: false,
// These next 5 lines are just to avoid the Bing Key error message.
imageryProvider : Cesium.createTileMapServiceImageryProvider({
url : Cesium.buildModuleUrl('Assets/Textures/NaturalEarthII')
}),
baseLayerPicker : false,
geocoder : false,
// This next line fixes another Stack Snippet error, you may omit
// this setting from production code as well.
infoBox : false
});
var numberOfArcs = 50;
var startLon = -74;
var startLat = 39;
viewer.clock.clockRange = Cesium.ClockRange.LOOP_STOP;
var startTime = viewer.clock.startTime;
var midTime = Cesium.JulianDate.addSeconds(startTime, 43200, new Cesium.JulianDate());
var stopTime = Cesium.JulianDate.addSeconds(startTime, 86400, new Cesium.JulianDate());
for (var i = 0; i < numberOfArcs; ++i) {
var color = Cesium.Color.fromRandom({
alpha : 1.0
});
var stopLon = Cesium.Math.nextRandomNumber() * 358 - 179;
var stopLat = Cesium.Math.nextRandomNumber() * 178 - 89;
// Create a straight-line path.
var property = new Cesium.SampledPositionProperty();
var startPosition = Cesium.Cartesian3.fromDegrees(startLon, startLat, 0);
property.addSample(startTime, startPosition);
var stopPosition = Cesium.Cartesian3.fromDegrees(stopLon, stopLat, 0);
property.addSample(stopTime, stopPosition);
// Find the midpoint of the straight path, and raise its altitude.
var midPoint = Cesium.Cartographic.fromCartesian(property.getValue(midTime));
midPoint.height = Cesium.Math.nextRandomNumber() * 500000 + 2500000;
var midPosition = viewer.scene.globe.ellipsoid.cartographicToCartesian(
midPoint, new Cesium.Cartesian3());
// Redo the path to be the new arc.
property = new Cesium.SampledPositionProperty();
property.addSample(startTime, startPosition);
property.addSample(midTime, midPosition);
property.addSample(stopTime, stopPosition);
// Create an Entity to show the arc.
var arcEntity = viewer.entities.add({
position : property,
// The point is optional, I just wanted to see it.
point : {
pixelSize : 8,
color : Cesium.Color.TRANSPARENT,
outlineColor : color,
outlineWidth : 3
},
// This path shows the arc as a polyline.
path : {
resolution : 1200,
material : new Cesium.PolylineGlowMaterialProperty({
glowPower : 0.16,
color : color
}),
width : 10,
leadTime: 1e10,
trailTime: 1e10
}
});
// This is where it becomes a smooth path.
arcEntity.position.setInterpolationOptions({
interpolationDegree : 5,
interpolationAlgorithm : Cesium.LagrangePolynomialApproximation
});
}
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html, body, #cesiumContainer {
width: 100%; height: 100%; margin: 0; padding: 0; overflow: hidden;
font-family: sans-serif;
}
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<link href="http://cesiumjs.org/releases/1.20/Build/Cesium/Widgets/widgets.css"
rel="stylesheet"/>
<script src="http://cesiumjs.org/releases/1.20/Build/Cesium/Cesium.js">
</script>
<div id="cesiumContainer"></div>
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答案 1 :(得分:1)
这里有类似的实现,但很难找到:
https://groups.google.com/forum/#!topic/cesium-dev/vr_ZH1yRNoQ