cesium 轨迹线

在智慧城市项目中，轨迹线一般用来表现城市道路的流动效果。和cesium动态线篇效果类似，只是这里是通过设置高亮占比，而不是通过传入一张图片。

1. 自定义TrialFlowMaterialProperty类

1.1. 自定义 TrialFlowMaterialProperty 类

/*
 * @Description: 
 * @Author: maizi
 * @Date: 2024-08-16 15:06:46
 * @LastEditTime: 2024-08-26 17:47:26
 * @LastEditors: maizi
 */

function TrialFlowMaterialProperty(options) {
  options = Cesium.defaultValue(options, Cesium.defaultValue.EMPTY_OBJECT);

  this._definitionChanged = new Cesium.Event();
  this._color = undefined;
  this._speed = undefined;
  this._ratio = undefined;
  this._tranparent = undefined;
 
  this.color = options.color || Cesium.Color.fromBytes(0, 255, 255, 255);
  this.speed = options.speed || 1;
  this.ratio = options.ratio || 0.2;
  this.tranparent = options.tranparent || 0.2;
}

Object.defineProperties(TrialFlowMaterialProperty.prototype, {
  isConstant: {
    get: function () {
      return (
        Cesium.Property.isConstant(this._color) 
        && Cesium.Property.isConstant(this._speed)
        && Cesium.Property.isConstant(this._ratio) 
        && Cesium.Property.isConstant(this._tranparent) 
      );
    },
  },

  definitionChanged: {
    get: function () {
      return this._definitionChanged;
    },
  },

  color: Cesium.createPropertyDescriptor("color"),
  speed: Cesium.createPropertyDescriptor("speed"),
  ratio: Cesium.createPropertyDescriptor("ratio"),
  tranparent: Cesium.createPropertyDescriptor("tranparent"),
});


TrialFlowMaterialProperty.prototype.getType = function (time) {
  return "TrialFlow";
};

TrialFlowMaterialProperty.prototype.getValue = function (time, result) {
  if (!Cesium.defined(result)) {
    result = {};
  }

  result.color = Cesium.Property.getValueOrClonedDefault(this._color, time);
  result.speed = Cesium.Property.getValueOrClonedDefault(this._speed, time);
  result.ratio = Cesium.Property.getValueOrUndefined(this._ratio, time);
  result.tranparent = Cesium.Property.getValueOrUndefined(this._tranparent, time);
  return result;
};


TrialFlowMaterialProperty.prototype.equals = function (other) {
  const res = this === other || (other instanceof TrialFlowMaterialProperty &&
    Cesium.Property.equals(this._color, other._color) &&
    Cesium.Property.equals(this._speed, other._speed))&&
    Cesium.Property.equals(this._ratio, other._ratio) &&
    Cesium.Property.equals(this._tranparent, other._tranparent)
  return res;
};
export default TrialFlowMaterialProperty;

1.2. 材质shader

uniform vec4 color;
uniform float speed;
uniform float ratio;
uniform float tranparent;

czm_material czm_getMaterial(czm_materialInput materialInput){
   czm_material material = czm_getDefaultMaterial(materialInput);
  vec2 st = materialInput.st;
  float time = fract(czm_frameNumber * speed / 1000.0);
  float alpha = smoothstep(time - ratio, time, st.s) * step(-time, -st.s);
  alpha += tranparent;
  material.diffuse= color.rgb;
  material.alpha = alpha;
  return material;
}

1.3. 添加到缓存

/*
 * @Description: 
 * @Author: maizi
 * @Date: 2024-08-16 16:21:55
 * @LastEditTime: 2024-08-26 18:00:42
 * @LastEditors: maizi
 */
import TrialFlowMaterial from '../shader/TrialFlowMaterial.glsl'

Cesium.Material.TrialFlow = 'TrialFlow'
Cesium.Material._materialCache.addMaterial(
  Cesium.Material.TrialFlow,
  {
    fabric: {
      type: Cesium.Material.TrialFlow,
      uniforms: {
        color: new Cesium.Color(1.0, 0.0, 0.0, 0.7),
        speed: 1,
        ratio: 0.2,
        tranparent: 0.2
      },
      source: TrialFlowMaterial,
    },
    translucent: function (material) {
      return true
    },
  }
)

2. 完整示例代码

TrialFlowLine.js

/*
 * @Description:
 * @Author: maizi
 * @Date: 2022-05-27 11:36:22
 * @LastEditTime: 2023-04-26 17:38:41
 * @LastEditors: maizi
 */
const merge = require('deepmerge')
import { TrialFlowMaterialProperty } from '../../materialProperty/index.js'
const defaultStyle = {
  speed: 10,
  ratio: 0.2,
  tranparent: 0.2,
  color: "#ffff00",
  lineWidth: 8
}

class TrialFlowLine {
  constructor(viewer, coords, options = {}) {
    this.viewer = viewer
    this.coords = coords;
    this.options = options;
    this.props = this.options.props;
    this.style = merge(defaultStyle, this.options.style || {});
   
    this.entity = null;
    this.material = null
    this.points = []
    this.init();
  }

  init() {
    this.createMaterial();
    this.entity = new Cesium.Entity({
      id: Math.random().toString(36).substring(2),
      type: "trial_flow_line",
      polyline: {
        positions: this.getPositons(),
        width: this.style.lineWidth,
        material: this.material,
        //clampToGround: true
      }
    });
  }

  addPoints() {
    this.coords.forEach((coord) => {
      const point = new Cesium.Entity({
        position: Cesium.Cartesian3.fromDegrees(coord[0],coord[1],coord[2]),
        point: {
          color: Cesium.Color.DARKBLUE.withAlpha(.4),
          pixelSize: 6,
          outlineColor: Cesium.Color.YELLOW.withAlpha(.8),
          outlineWidth: 4
        }     
      }); 
      this.viewer.entities.add(point)
      this.points.push(point)
    })
  }

  removePoints() {
    this.points.forEach((point) => {
      this.viewer.entities.remove(point)
    })
    this.points = []
  }

  getPositons() {
    const positions = []
    this.coords.forEach((coord) => {
      positions.push(Cesium.Cartesian3.fromDegrees(coord[0], coord[1], coord[2]));
    })
    return positions
  }

  createMaterial() {
    this.material = new TrialFlowMaterialProperty({
      color: new Cesium.Color.fromCssColorString(this.style.color),
      speed:this.style.speed,
      ratio: this.style.ratio,
      tranparent: this.style.tranparent
    });
  }

  updateStyle(style) {
    this.style = merge(defaultStyle, style);
    this.entity.polyline.width = this.style.lineWidth
    this.material.color = new Cesium.Color.fromCssColorString(this.style.color)
    this.material.speed = this.style.speed
    this.material.ratio = this.style.ratio
    this.material.tranparent = this.style.tranparent
  }

  setSelect(enabled) {
    if (enabled) {
      this.addPoints()
    } else {
      this.removePoints()
    }
  }
}

export {
  TrialFlowLine
}

MapWorks.js

import GUI from 'lil-gui'; 
// 初始视图定位在中国
import { TrialFlowLine } from './TrialFlowLine'

Cesium.Camera.DEFAULT_VIEW_RECTANGLE = Cesium.Rectangle.fromDegrees(90, -20, 110, 90);

let viewer = null;
let graphicLayer = null
let graphicList = []
let selectGraphic = null
let eventHandler = null
let gui = null

function initMap(container) {
  viewer = new Cesium.Viewer(container, {
    animation: false,
    baseLayerPicker: false,
    fullscreenButton: false,
    geocoder: false,
    homeButton: false,
    infoBox: false,
    sceneModePicker: false,
    selectionIndicator: false,
    timeline: false,
    navigationHelpButton: false, 
    scene3DOnly: true,
    orderIndependentTranslucency: false,
    contextOptions: {
      webgl: {
        alpha: true
      }
    }
  })
  viewer._cesiumWidget._creditContainer.style.display = 'none'
  viewer.scene.fxaa = true
  viewer.scene.postProcessStages.fxaa.enabled = true
  if (Cesium.FeatureDetection.supportsImageRenderingPixelated()) {
    // 判断是否支持图像渲染像素化处理
    viewer.resolutionScale = window.devicePixelRatio
  }
  // 移除默认影像
  removeAll()
  // 地形深度测试
  viewer.scene.globe.depthTestAgainstTerrain = true
  // 背景色
  viewer.scene.globe.baseColor = new Cesium.Color(0.0, 0.0, 0.0, 0)
  // 太阳光照
  viewer.scene.globe.enableLighting = true;

  // 初始化图层
  initLayer()
  // 初始化鼠标事件
  initClickEvent()
  //调试
  window.viewer = viewer
}

function initGui() {
  let params = {
    ...selectGraphic.style
  }
  gui = new GUI()
  let layerFolder = gui.title('样式设置')
  layerFolder.add(params, 'speed', 0, 100).step(1.0).onChange(function (value) {
    selectGraphic.updateStyle(params)
  })
  layerFolder.add(params, 'ratio', 0, 1.0).step(0.01).onChange(function (value) {
    selectGraphic.updateStyle(params)
  })
  layerFolder.add(params, 'tranparent', 0, 1.0).step(0.01).onChange(function (value) {
    selectGraphic.updateStyle(params)
  })
  layerFolder.add(params, 'lineWidth', 1, 30).step(1).onChange(function (value) {
    selectGraphic.updateStyle(params)
  })
  layerFolder.addColor(params, 'color').onChange(function (value) {
    selectGraphic.updateStyle(params)
  })
}


function initLayer() {
  const layerProvider = new Cesium.ArcGisMapServerImageryProvider({
    url: 'https://services.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer'
  });
  viewer.imageryLayers.addImageryProvider(layerProvider);
  graphicLayer = new Cesium.CustomDataSource('graphicLayer')
  viewer.dataSources.add(graphicLayer)
}

function loadTrialFlowLine(lines) {
  lines.forEach(line => {
    const trialFlowLine = new TrialFlowLine(viewer, line.points)
    graphicList.push(trialFlowLine)
    graphicLayer.entities.add(trialFlowLine.entity)
  });
  viewer.flyTo(graphicLayer)
}

function initClickEvent() {
  eventHandler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
  initLeftClickEvent()
  initMouseMoveEvent()
}

function initLeftClickEvent() {
  eventHandler.setInputAction((e) => {
    if (selectGraphic) {
      selectGraphic.setSelect(false)
      selectGraphic = null
    }
    if (gui) {
      gui.destroy()
    }
    let pickedObj = viewer.scene.pick(e.position);
    if (pickedObj && pickedObj.id) {
      if (pickedObj.id.type === 'trial_flow_line') {
        selectGraphic = getGraphicById(pickedObj.id.id)
        if (selectGraphic) {
          selectGraphic.setSelect(true)
          initGui()
        }
      }
    }
  },Cesium.ScreenSpaceEventType.LEFT_CLICK)
}

function initMouseMoveEvent() {
  eventHandler.setInputAction((e) => {
    const pickedObj = viewer.scene.pick(e.endPosition);
    if (pickedObj && pickedObj.id) {
      if (pickedObj.id.type === 'trial_flow_line') {
        // 改变鼠标状态
        viewer._element.style.cursor = "";
        document.body.style.cursor = "pointer";
      } else {
        viewer._element.style.cursor = "";
        document.body.style.cursor = "default";
      }
    } else {
      viewer._element.style.cursor = "";
      document.body.style.cursor = "default";
    }
  },Cesium.ScreenSpaceEventType.MOUSE_MOVE)
}

function getGraphicById(id) {
  let line = null
  for (let i = 0; i < graphicList.length; i++) {
    if (graphicList[i].entity.id === id) {
      line = graphicList[i]
      break
    } 
  }
  return line
}

function removeAll() {
  viewer.imageryLayers.removeAll();
}

function destroy() {
  viewer.entities.removeAll();
  viewer.imageryLayers.removeAll();
  viewer.destroy();
}




export {
  initMap,
  loadTrialFlowLine,
  destroy
}

TrialFlowLine.vue

<!--
 * @Description: 
 * @Author: maizi
 * @Date: 2023-04-07 17:03:50
 * @LastEditTime: 2024-08-26 18:00:57
 * @LastEditors: maizi
-->

<template>
  <div id="container">
  </div>
</template>

<script>
import * as MapWorks from './js/MapWorks'
export default {
  name: 'TrialFlowLine',
  mounted() {
    this.init();
  },
  methods:{
    init(){
      let container = document.getElementById("container");
      MapWorks.initMap(container)
      //创建
      let lines = [
        {
          points: [
            [104.068822,30.654807,10],
            [104.088822,30.654807,10],
          ]
        },
        {
          points: [
            [104.068822,30.655807,10],
            [104.088822,30.655807,10],
          ]
        },
      ];
      MapWorks.loadTrialFlowLine(lines)
    }
  },

  beforeDestroy(){
    //实例被销毁前调用，页面关闭、路由跳转、v-if和改变key值
    MapWorks.destroy();
  }
}
</script>

<style lang="scss" scoped>
#container{
  width: 100%;
  height: 100%;
  background: rgba(7, 12, 19, 1);
  overflow: hidden;
  background-size: 40px 40px, 40px 40px;
  background-image: linear-gradient(hsla(0, 0%, 100%, 0.05) 1px, transparent 0), linear-gradient(90deg, hsla(0, 0%, 100%, 0.05) 1px, transparent 0);
}


</style>