cesium实现竖直随机飞线效果

文章目录

    • 1.实现效果
    • 2.实现方法
      • 2.1材质实现
      • 2.2随机点生成
      • 2.2代码调用

Cesium实战系列文章总目录:传送门

1.实现效果

2.实现方法

通过生成随机线,并设置飞线材质即可。

2.1材质实现

飞线材质lineFlowMaterialProperty.js:

/*
 * @Description: 飞线效果(参考开源代码)
 * @Version: 1.0
 * @Author: Julian
 * @Date: 2022-03-05 16:13:21
 * @LastEditors: Julian
 * @LastEditTime: 2022-03-05 17:39:38
 */
class LineFlowMaterialProperty {
    constructor(options) {
        this._definitionChanged = new Cesium.Event();
        this._color = undefined;
        this._speed = undefined;
        this._percent = undefined;
        this._gradient = undefined;
        this.color = options.color;
        this.speed = options.speed;
        this.percent = options.percent;
        this.gradient = options.gradient;
    };

    get isConstant() {
        return false;
    }

    get definitionChanged() {
        return this._definitionChanged;
    }

    getType(time) {
        return Cesium.Material.LineFlowMaterialType;
    }

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

        result.color = Cesium.Property.getValueOrDefault(this._color, time, Cesium.Color.RED, result.color);
        result.speed = Cesium.Property.getValueOrDefault(this._speed, time, 5.0, result.speed);
        result.percent = Cesium.Property.getValueOrDefault(this._percent, time, 0.1, result.percent);
        result.gradient = Cesium.Property.getValueOrDefault(this._gradient, time, 0.01, result.gradient);
        return result
    }

    equals(other) {
        return (this === other ||
            (other instanceof LineFlowMaterialProperty &&
                Cesium.Property.equals(this._color, other._color) &&
                Cesium.Property.equals(this._speed, other._speed) &&
                Cesium.Property.equals(this._percent, other._percent) &&
                Cesium.Property.equals(this._gradient, other._gradient))
        )
    }
}

Object.defineProperties(LineFlowMaterialProperty.prototype, {
    color: Cesium.createPropertyDescriptor('color'),
    speed: Cesium.createPropertyDescriptor('speed'),
    percent: Cesium.createPropertyDescriptor('percent'),
    gradient: Cesium.createPropertyDescriptor('gradient'),
})

Cesium.LineFlowMaterialProperty = LineFlowMaterialProperty;
Cesium.Material.LineFlowMaterialProperty = 'LineFlowMaterialProperty';
Cesium.Material.LineFlowMaterialType = 'LineFlowMaterialType';
Cesium.Material.LineFlowMaterialSource =
    `
    uniform vec4 color;
    uniform float speed;
    uniform float percent;
    uniform float gradient;
    
    czm_material czm_getMaterial(czm_materialInput materialInput){
      czm_material material = czm_getDefaultMaterial(materialInput);
      vec2 st = materialInput.st;
      float t =fract(czm_frameNumber * speed / 1000.0);
      t *= (1.0 + percent);
      float alpha = smoothstep(t- percent, t, st.s) * step(-t, -st.s);
      alpha += gradient;
      material.diffuse = color.rgb;
      material.alpha = alpha;
      return material;
    }
    `

Cesium.Material._materialCache.addMaterial(Cesium.Material.LineFlowMaterialType, {
    fabric: {
        type: Cesium.Material.LineFlowMaterialType,
        uniforms: {
            color: new Cesium.Color(1.0, 0.0, 0.0, 1.0),
            speed: 10.0,
            percent: 0.1,
            gradient: 0.01
        },
        source: Cesium.Material.LineFlowMaterialSource
    },
    translucent: function(material) {
        return true;
    }
})

2.2随机点生成

通过random函数,生成中心点周围的随机点位。

/**
 * @description: 产生随机点
 * @param {*} position:中心点坐标
 * @param {*} num:随机点数量
 * @return {*}
 */
function generateRandomPosition(position, num) {
    let list = []
    for (let i = 0; i < num; i++) {
        // random产生的随机数范围是0-1,需要加上正负模拟
        let lon = position[0] + Math.random() * 0.04 * (i % 2 == 0 ? 1 : -1);
        let lat = position[1] + Math.random() * 0.04 * (i % 2 == 0 ? 1 : -1);
        list.push([lon, lat])
    }
    return list
}

2.2代码调用

引入材质js文件后,通过生成的随机点设置随机高度生成随机线,并设置其材质即可。
这里把调用函数封装成了lineFlowInit函数,代码如下。

// 随机竖直飞线
lineFlowInit(this.viewer, [113.9236839, 22.528061], 120);

/**
 * @description: 竖直随机飞线初始化
 * @param {*} _viewer
 * @param {*} _center :中心点
 * @param {*} _num :数量
 * @return {*}
 */
function lineFlowInit(_viewer, _center, _num) {
    let _positions = generateRandomPosition(_center, _num);
    _positions.forEach(item => {
        // 经纬度
        let start_lon = item[0];
        let start_lat = item[1];

        let startPoint = new Cesium.Cartesian3.fromDegrees(start_lon, start_lat, 0);

        // 随机高度
        let height = 5000 * Math.random();
        let endPoint = new Cesium.Cartesian3.fromDegrees(start_lon, start_lat, height);
        let linePositions = [];
        linePositions.push(startPoint);
        linePositions.push(endPoint);
        _viewer.entities.add({
            polyline: {
                positions: linePositions,
                material: new Cesium.LineFlowMaterialProperty({
                    color: new Cesium.Color(1.0, 1.0, 0.0, 0.8),
                    speed: 15 * Math.random(),
                    percent: 0.1,
                    gradient: 0.01
                })
            }
        })
    })
}

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