Interpolation

<!--
  示例：采样属性的插值
  说明：同一条折线分别用线性、拉格朗日与埃尔米特插值，路径弯曲程度不同
  核心逻辑：SampledPositionProperty → setInterpolationOptions → 三个实体同时推进
  依赖：CesiumJS 1.121 · jsDelivr CDN
-->
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta name="robots" content="noindex,follow">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>采样属性的插值</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/cesium@1.121.0/Build/Cesium/Widgets/widgets.css">
<style>
  html,body{height:100%;margin:0}
  body{background:#0e1116;color:#e6e8ec;overflow:hidden;
       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif}
  #c{height:100%}
  .tip{position:absolute;left:12px;top:12px;z-index:5;
       background:rgba(23,28,35,.9);border:1px solid #2a313b;border-radius:6px;
       padding:8px 12px;font-size:12px;color:#a2a9b6;max-width:320px;line-height:1.6}

  .cesium-viewer-bottom .cesium-widget-credits,.cesium-viewer-animationContainer,
  .cesium-viewer-timelineContainer{display:none!important}
</style>
</head>
<body>
<div id="c"></div>
<div class="tip">三种插值用同样的采样点，曲线形状却不同，拉格朗日最平滑。</div>
<script src="https://cdn.jsdelivr.net/npm/cesium@1.121.0/Build/Cesium/Cesium.js"></script>
<script>
(function () {
  'use strict';

  var viewer = new Cesium.Viewer('c', {
    baseLayer: false,
    baseLayerPicker: false, geocoder: false, homeButton: false,
    sceneModePicker: false, navigationHelpButton: false,
    animation: false, timeline: false, fullscreenButton: false,
    infoBox: false, selectionIndicator: false
  });

  var scene = viewer.scene;
  scene.globe.baseColor = Cesium.Color.fromCssColorString('#1c2733');
  scene.backgroundColor = Cesium.Color.fromCssColorString('#0e1116');
  scene.skyBox.show = false;
  scene.sun.show = false;
  scene.moon.show = false;
  if (scene.skyAtmosphere) scene.skyAtmosphere.show = false;

  var start = Cesium.JulianDate.fromIso8601('2026-10-28T00:00:00Z');
  viewer.clock.startTime = start.clone();
  viewer.clock.stopTime = Cesium.JulianDate.addSeconds(start, 20, new Cesium.JulianDate());
  viewer.clock.currentTime = start.clone();
  viewer.clock.clockRange = Cesium.ClockRange.LOOP_STOP;
  viewer.clock.multiplier = 1;
  viewer.clock.shouldAnimate = true;

  var samples = [
    [116.383, 39.9015, 30], [116.386, 39.9035, 55],
    [116.389, 39.9020, 90], [116.392, 39.9045, 60], [116.395, 39.9025, 35]
  ];

  function build(algorithm, color) {
    var prop = new Cesium.SampledPositionProperty();
    prop.setInterpolationOptions({
      interpolationDegree: algorithm === Cesium.InterpolationAlgorithm.LAGRANGE ? 3 : 1,
      interpolationAlgorithm: algorithm
    });
    for (var i = 0; i < samples.length; i++) {
      prop.addSample(
        Cesium.JulianDate.addSeconds(start, i * 5, new Cesium.JulianDate()),
        Cesium.Cartesian3.fromDegrees(samples[i][0], samples[i][1], samples[i][2])
      );
    }
    viewer.entities.add({
      position: prop,
      point: {
        pixelSize: 12,
        color: Cesium.Color.fromCssColorString(color),
        outlineColor: Cesium.Color.WHITE,
        outlineWidth: 2,
        disableDepthTestDistance: Number.POSITIVE_INFINITY
      },
      path: { resolution: 1, width: 2, material: Cesium.Color.fromCssColorString(color).withAlpha(0.7) },
      label: {
        text: '',
        font: '600 12px sans-serif',
        fillColor: Cesium.Color.WHITE,
        pixelOffset: new Cesium.Cartesian2(0, -24),
        disableDepthTestDistance: Number.POSITIVE_INFINITY
      }
    });
  }

  build(Cesium.InterpolationAlgorithm.LINEAR, '#4d86c8');
  build(Cesium.InterpolationAlgorithm.LAGRANGE, '#5bb08a');
  build(Cesium.InterpolationAlgorithm.HERMITE, '#d08a4e');
  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.389, 39.8994, 520),
    orientation: { heading: Cesium.Math.toRadians(0), pitch: Cesium.Math.toRadians(-24), roll: 0 },
    duration: 0
  });
})();
</script>
</body>
</html>