# Performance issues with entity animation
**URL:** https://community.cesium.com/t/performance-issues-with-entity-animation/3021
**Category:** CesiumJS
**Created:** [September 3, 2015, 7:49am UTC](https://community.cesium.com/t/performance-issues-with-entity-animation/3021 "2015-09-03T07:49:20Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@u12047822](https://community.cesium.com/u/u12047822)
#### Post date: [September 3, 2015, 7:49am UTC](https://community.cesium.com/t/performance-issues-with-entity-animation/3021/1 "2015-09-03T07:49:20Z")
Hey guys,
We're working on a university project where we are developing a satellite orbit viewer, which has to display the satellites' footprints.
Currently we're using JavaScript's setInterval function to update the footprint's position whenever the satellite moves. We've implemented it as follows:
Here is how the footprint entity is created:
var currentAreaOnEarth =
{
position: Cesium.Cartesian3.fromDegrees(satPosition[0], satPosition[1]),
ellipse: {
semiMinorAxis: 250 \* footprint,
semiMajorAxis: 250 \* footprint,
outline: true,
outlineColor: Cesium.Color.RED,
outlineWidth: 4,
material: stripeMaterial
}
}
Here is were the setInterval for animation is configured:
function animate() {
Satellites.animateCurrentAreaOnEarth(cesiumViewer);
Satellites.updateSatelliteInformation(cesiumViewer);
};
setInterval(animate, 150);
This is the function that does the updating of the entity's position at each interval:
animateCurrentAreaOnEarth: function (cesiumViewer)
{
for (var i = 0; i \< this.arrayOfSatellites.length; ++i)
{
if(this.satelliteFootprints[i].show == true)
{
var satPosition = this.showSatellitePosition(cesiumViewer, i);
this.satelliteFootprints[i].position = Cesium.Cartesian3.fromDegrees(satPosition[0], satPosition[1]);
}
}
}
The problem we are experiencing is that with many satellites the setInterval method causes a large performance hit. We were wondering if you could help us with how to animate these footprints similar to how the satellite entities are animated, or a way to attach these footprints to the satellite entities so that they move with the satellites themselves.
Thank you for any help you can provide us!
---
### Author:  [@hannah](https://community.cesium.com/u/hannah)
#### Post date: [September 3, 2015, 6:52pm UTC](https://community.cesium.com/t/performance-issues-with-entity-animation/3021/2 "2015-09-03T18:52:24Z")
Hello,
I think this is because your ellipses are being computed asynchronously in a web worker. This is because the entity collection thinks the ellipse is going to be static since it has all static properties. To get around this, we can use a [CallbackProperty](http://cesiumjs.org/Cesium/Build/Documentation/CallbackProperty.html) for the positions argument to let the entity collection know it is going to be changing. See the example below:
var currentAreaOnEarth =
{
position: new Cesium.CallbackProperty(getEllipsePosition, false),
ellipse: {
semiMinorAxis: 250 \* footprint,
semiMajorAxis: 250 \* footprint,
outline: true,
outlineColor: Cesium.Color.RED,
outlineWidth: 4,
material: stripeMaterial
}
}
function getEllipsePosition() {
return Cesium.Cartesian3.fromDegrees(satPosition[0], satPosition[1]);
}
``
Best,
Hannah
---
### Author:  [@u12047822](https://community.cesium.com/u/u12047822)
#### Post date: [September 4, 2015, 9:52am UTC](https://community.cesium.com/t/performance-issues-with-entity-animation/3021/3 "2015-09-04T09:52:19Z")
Hi Hannah,
That solved the problem, thank you so much for the help!