Material Water

<!--
  示例：用自定义着色器材質做水波面
  要点：Material 的 fabric.source 写 czm_getMaterial，靠 czm_frameNumber 自动随时间流动
  依赖：CesiumJS 1.121 · jsDelivr CDN，波纹在片元着色器里计算
-->
<!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>程序水波材质</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%}
  .hud{position:absolute;left:12px;top:12px;z-index:5;background:rgba(23,28,35,.9);
       border:1px solid #2a313b;border-radius:6px;padding:9px 12px;font-size:12px;
       color:#a2a9b6;max-width:250px}
  .hud b{color:#e6e8ec;font-weight:600}
  .hud .row{margin-top:6px;color:#7f8896}
  .cesium-viewer-bottom .cesium-widget-credits,.cesium-viewer-animationContainer,
  .cesium-viewer-timelineContainer{display:none!important}
</style>
</head>
<body>
<div id="c"></div>
<div class="hud">
  <div><b>着色器水波</b></div>
  <div class="row">表面颜色与波纹由 GLSL 计算</div>
  <div class="row">时间取自 czm_frameNumber</div>
  <div class="row">池底与堤岸用图元铺出</div>
</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;

  /* 片元着色器：两组正弦波叠加，按波峰给颜色插值 */
  var SOURCE = [
    'czm_material czm_getMaterial(czm_materialInput materialInput) {',
    '  czm_material material = czm_getDefaultMaterial(materialInput);',
    '  vec2 st = materialInput.st;',
    '  float t = czm_frameNumber * 0.02;',
    '  float w1 = sin(st.x * 26.0 + st.y * 8.0 + t);',
    '  float w2 = sin(st.x * 9.0 - st.y * 34.0 - t * 1.7);',
    '  float wave = (w1 + w2) * 0.5;',
    '  vec3 deep = vec3(0.02, 0.17, 0.30);',
    '  vec3 crest = vec3(0.40, 0.80, 0.96);',
    '  material.diffuse = mix(deep, crest, smoothstep(-0.85, 0.95, wave));',
    '  material.alpha = 0.92;',
    '  return material;',
    '}'
  ].join('\n');

  var waterMaterial = new Cesium.Material({
    fabric: {
      type: 'WaterRipple',
      uniforms: {},
      source: SOURCE
    }
  });

  /* 水面几何：一块贴地的多边形，带 st 坐标才能用材质着色器 */
  var water = new Cesium.Primitive({
    geometryInstances: new Cesium.GeometryInstance({
      geometry: Cesium.PolygonGeometry.createGeometry(new Cesium.PolygonGeometry({
        polygonHierarchy: new Cesium.PolygonHierarchy(
          Cesium.Cartesian3.fromDegreesArray([
            116.376, 39.900,
            116.402, 39.900,
            116.402, 39.918,
            116.376, 39.918
          ])
        ),
        height: 4,
        vertexFormat: Cesium.EllipsoidSurfaceAppearance.VERTEX_FORMAT
      }))
    }),
    appearance: new Cesium.EllipsoidSurfaceAppearance({
      material: waterMaterial,
      aboveGround: true
    })
  });
  scene.primitives.add(water);

  /* 池底：稍低一点的深色面，衬托水面 */
  viewer.entities.add({
    polygon: {
      hierarchy: Cesium.Cartesian3.fromDegreesArray([
        116.374, 39.898, 116.404, 39.898, 116.404, 39.920, 116.374, 39.920
      ]),
      height: 0,
      material: Cesium.Color.fromCssColorString('#101820')
    }
  });

  /* 堤岸：四条盒子围边 */
  var EDGES = [
    [116.376, 39.900, 116.402, 39.900],
    [116.402, 39.900, 116.402, 39.918],
    [116.402, 39.918, 116.376, 39.918],
    [116.376, 39.918, 116.376, 39.900]
  ];
  EDGES.forEach(function (e) {
    viewer.entities.add({
      polylineVolume: {
        positions: Cesium.Cartesian3.fromDegreesArrayHeights([
          e[0], e[1], 0, e[2], e[3], 0
        ]),
        shape: [
          new Cesium.Cartesian2(-6, 0), new Cesium.Cartesian2(6, 0),
          new Cesium.Cartesian2(6, 14), new Cesium.Cartesian2(-6, 14)
        ],
        material: Cesium.Color.fromCssColorString('#2c3a4a')
      }
    });
  });

  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.389, 39.889, 1500),
    orientation: {
      heading: Cesium.Math.toRadians(0),
      pitch: Cesium.Math.toRadians(-26),
      roll: 0
    },
    duration: 0
  });
})();
</script>
</body>
</html>