Cesium 实时目标跟踪最新特效教程系列3—实时波束扫描（仿圆锥形波束扫描）

sourEntity实时波束扫描跟踪tarEntity，思路：利用12个多边形（扇形）组成圆锥波束，然后实时更新根据目标位置更新每个扇形的位置达到圆锥波束

function moveTc(sourEntity,tarEntity){
var isConstant = false;
var sourceColor = tarEntity.model.color;
var tcColor = Cesium.Color.fromAlpha(Cesium.Color.RED,
parseFloat(0.5));
var colors = Cesium.Color.fromRandom({alpha : 0.4});
for(var k = 0 ; k < 36 ; k += 3){
  Cesium.when(k).then(function(k){
      viewer.entities.add( {
       polygon : {
        hierarchy  : new Cesium.CallbackProperty(function(time, result) {
                      if(yzentities.length != 0){
                        for(var i = 0 ; i < yzentities.length; i++){
                           viewer.entities.remove(yzentities[i]);
                        }
                        
                     }
                     var time = viewer.clock.currentTime; 
                     var position= tarEntity.position.getValue(time); 
                     if(!Cesium.defined(tarEntity)){
                      return Cesium.Cartesian3.fromDegreesArrayHeights([]);
                     }
                     if(!Cesium.defined(position)){
                      return Cesium.Cartesian3.fromDegreesArrayHeights([]);
                     }
                  
                    var cartographic = viewer.scene.globe.ellipsoid.
cartesianToCartographic(position);
var ecLat=Cesium.Math.toDegrees(cartographic.latitude);

                  var ecLong=Cesium.Math.toDegrees(cartographic.longitude);
                  var alt=cartographic.height;
                   var sourPos= sourEntity.position.getValue(time,result);
                   var cartographic1 = viewer.scene.globe.ellipsoid.
cartesianToCartographic(sourPos);
               var sourLon=Cesium.Math.toDegrees(cartographic1.longitude);
               var sourLat=Cesium.Math.toDegrees(cartographic1.latitude);
                     var souralt=cartographic1.height;

                     var r = 60;//半径
                     var color = '#0000FF';
                     var finalArr = [];
                     //模拟光照效果的若干多边形
                     var points = [];
                     for ( var i = 0; i < 360; i += 30 )
                     {
                        var coord = offsetToLongLat( [
                           ecLong, ecLat
                        ], [Math.cos( Math.PI * i / 180 ) * r, Math.sin( Math.PI * i / 180 ) * r] );
                        points.push( coord[0] );
                        points.push( coord[1] );
                        points.push( alt );
                     }
                     
                    var array = [sourLon, sourLat, souralt, points[k], points[k + 1], points[k + 2] ];
                        if ( k + 3 == points.length )
                        {
                           array.push( points[0] );
                           array.push( points[1] );
                           array.push( points[2] );
                        }
                        else
                        {
                           array.push( points[k + 3] );
                           array.push( points[k + 4] );
                           array.push( points[k + 5] );
                        }
                 return Cesium.Cartesian3.fromDegreesArrayHeights( array );
                },isConstant),
                  perPositionHeight : true,
                  outline : false,
                  material : colors
                }
            });
         })
        
          
            
      }
        
       
}