Cesium Entities SamplePositionProperty

Cesium Entities SamplePositionProperty.markdown

Cesium Entities SamplePositionProperty

Sample for Cesium forum post https://groups.google.com/forum/#!topic/cesium-dev/77WoQoGWYeU

A Pen by Michael Lodge-Paolini on CodePen.

License.

index.html

<div id="cesiumContainer" class="fullScreen">
  <div>

script.js

    var viewer = new Cesium.Viewer('cesiumContainer', {
      infoBox: false
    });
    var entities = viewer.entities;

    var duration = 100; //seconds
    var frequency = 100; //hertz

    var start = Cesium.JulianDate.fromDate(new Date());
    var stop = Cesium.JulianDate.addSeconds(start, duration, new Cesium.JulianDate());

    viewer.clock.startTime = start.clone();
    viewer.clock.stopTime = stop.clone();
    viewer.clock.currentTime = start.clone();
    viewer.clock.clockRange = Cesium.ClockRange.LOOP_STOP; //Loop at the end
    viewer.clock.multiplier = 10;
    viewer.timeline.zoomTo(start, stop);

    var point = {
      lat: 40.0,
      lon: -75.0
    };
    var finalPoint = {
      lat: 40.0,
      lon: -175.0
    };

    //generate a collection of position samples
    var positions = calculatePositionSamples(point, finalPoint, start, duration, frequency);

    //create the entity
    var target = entities.add({
      //Use our computed positions
      position: positions,

      //Automatically compute orientation based on position movement.
      orientation: new Cesium.VelocityOrientationProperty(positions),

      //Show the path
      path: {
        resolution: 1,
        material: new Cesium.PolylineGlowMaterialProperty({
          glowPower: 0.1,
          color: Cesium.Color.RED
        }),
        width: 5,
        trailTime: duration,
        leadTime: 0
      }
    });

    viewer.zoomTo(viewer.entities);
    viewer.trackEntity = target;

    /**
     * @param point {{lat:number, lon:number }}
     * @param endPoint {{lat:number, lon:number }}
     * @param startTime {Cesium.JulianDate}
     * @param duration {number} Seconds to calculate for
     * @param intervalCount {number}
     * @return property {Cesium.SampledPositionProperty}
     */
    function calculatePositionSamples(point, endPoint, startTime, duration, intervalCount) {
      var property = new Cesium.SampledPositionProperty();
      var deltaStep = duration / (intervalCount > 0 ? intervalCount : 1);

      var delta = {
        lon: (endPoint.lon - point.lon) / intervalCount,
        lat: (endPoint.lat - point.lat) / intervalCount
      };

      for (var since = 0; since <= duration; since += deltaStep) {
        property.addSample(
          Cesium.JulianDate.addSeconds(startTime, since, new Cesium.JulianDate()),
          Cesium.Cartesian3.fromDegrees(point.lon += delta.lon, point.lat += delta.lat)
        );
      }
      return property;
    }

scripts

<script src="http://cesiumjs.org/Cesium/Build/Cesium/cesium.js"></script>

style.css

.fullScreen {
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  border: none;
  width: 100%;
  height: 100%;
}

styles

<link href="http://cesiumjs.org/Cesium/Build/Cesium/Widgets/widgets.css" rel="stylesheet" />