Star Burst

<!--
  示例：点击爆出的星芒
  说明：点击地球上任意位置，以落点为中心炸出一圈放射状星芒
  核心逻辑：PostProcessStage 自定义 center 与 progress → 点击拾取换算屏幕坐标 → 逐帧推进进度
  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>点击爆出的星芒</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">点击球面上任意一点，星芒以落点为中心扩散后淡出。</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;

  /* 点击位置（0 到 1 的屏幕坐标）与扩散进度 */
  var center = new Cesium.Cartesian2(0.5, 0.5);
  var progress = 0.0;

  var stage = scene.postProcessStages.add(new Cesium.PostProcessStage({
    uniforms: { center: center, progress: progress },
    fragmentShader: [
      'uniform sampler2D colorTexture;',
      'uniform vec2 center;',
      'uniform float progress;',
      'in vec2 v_textureCoordinates;',
      'void main() {',
      '  vec2 d = v_textureCoordinates - center;',
      '  d.x *= 1.6;',
      '  float r = length(d);',
      '  float a = atan(d.y, d.x);',
      '  float rays = pow(abs(sin(a * 10.0)), 12.0);',
      '  float edge = smoothstep(progress - 0.18, progress, r)',
      '             * (1.0 - smoothstep(progress, progress + 0.01, r));',
      '  float fade = 1.0 - smoothstep(0.25, 0.55, progress);',
      '  float burst = rays * edge * fade;',
      '  vec4 color = texture(colorTexture, v_textureCoordinates);',
      '  out_FragColor = vec4(color.rgb + vec3(1.0, 0.86, 0.55) * burst * 1.4, color.a);',
      '}'
    ].join('\n')
  }));

  /* 进度从 0 走到 0.55，走完停住 */
  var running = false;
  scene.postRender.addEventListener(function () {
    if (!running) return;
    progress += 0.012;
    if (progress >= 0.55) { progress = 0.55; running = false; }
    stage.uniforms.progress = progress;
  });

  var handler = new Cesium.ScreenSpaceEventHandler(scene.canvas);
  handler.setInputAction(function (click) {
    var cartesian = scene.pickPosition(click.position);
    if (!Cesium.defined(cartesian)) {
      cartesian = viewer.camera.pickEllipsoid(click.position, Cesium.Ellipsoid.WGS84);
    }
    if (!Cesium.defined(cartesian)) return;
    var win = Cesium.SceneTransforms.worldToWindowCoordinates(scene, cartesian);
    if (!Cesium.defined(win)) return;
    center.x = win.x / scene.canvas.clientWidth;
    center.y = 1.0 - win.y / scene.canvas.clientHeight;
    progress = 0.0;
    running = true;
    stage.uniforms.center = center;
  }, Cesium.ScreenSpaceEventType.LEFT_CLICK);
  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.4, 39.9, 18000000),
    orientation: { heading: 0, pitch: Cesium.Math.toRadians(-90), roll: 0 },
    duration: 0
  });
})();
</script>
</body>
</html>