在Cesium中移动KML对象而不会闪烁

Question

I'm porting an existing Google Earth application to Cesium. The application tracks the position of a vehicle over time. Some base kml is loaded at first to show the overall track of the vehicle. Then a kml file is continuously updated with a placemark which shows the current position of the vehicle.

Currently, I am able to achieve the desired effect of moving the placmark in Cesium by adding the updated kml and removing the old kml every time it changes. The problem is that the placemark seems to flash or glitch each time that I reload it.

I had a similar issue in Google Earth which I solved by moving the existing KML instead of adding and deleting each time it changed. I'd like to find a way to do the same with Cesium. I've tried looking into the entity objects associated with the KmlDataSource but I can't see any way to move them. I was able to find the associated primitive available through the scene but I was not able to determine how to make it move.

Below is the snippet I use to add and remove the kml.

var pparser = new DOMParser();
var newPositionDataSource = new Cesium.KmlDataSource();
var prom = newPositionDataSource.load(parser.parseFromString(testkml, "text/xml"));
viewer.dataSources.add(newPositionDataSource);

if (positionDataSource != null)
{
    Cesium.when(prom, function()
    {
        viewer.dataSources.remove(positionDataSource);
    });
}
positionDataSource = newPositionDataSource;

Answer 1

I got this to work for placemarks. Emackey's suggestion was a good one. I modified my code so that I only add the KML for the placemark once. For each position update after the first I load in the new KML and set the original data source entity's position equal to that of the new KML data source.

This allows the placemark to move smoothly without glitching and saves me the trouble of manually parsing the KML. It works great for the placemarks.

Unfortunately, I have a couple of lines connecting the placemarks and they still glitch as it updates. If anyone has any ideas about how the line glitching could be prevented, I would be happy to read them.