Moving an object smoothly from A to B: simple example?

CesiumJS
1

Hello,

another request for help, from a Cesium newbie / Google Earth migrant:

Would someone please point me to a simple and complete (HTML, Javascript, and all) example of how to move an object (specifically the camera) from point A to point B in Cesium as smoothly as possible, with the following restraints (if at all feasible):

-- should not use flyTo()
   (because I'd like to avoid the "kangaroo jump" effect;
   see https://groups.google.com/forum/#!topic/cesium-dev/r6EstN51kNo

-- should not use CZML
   (I'll certainly look into it later, but not yet... :-))

-- should not require full understanding and/or modification
   of the source code in Cesium.js
   (ditto)

-- should work with the current Cesium v. 1.7.1

I have looked at the tutorials, the demos, even at the CZML Guide, and have searched this forum, but got lost in the jungle a bit, and couldn't find a simple enough (for me) example.

An additional problem is that apparently things have changed considerably recently. E.g. I did find a forum post (from 2013) describing what I was looking for, but when trying to run the animation, found that e.g. update() is no longer there, or perhaps behaves differently now. In general it seems that a lot has changed specifically with regard to animations.

So, any pointers to simple, practical, and up-to-date examples would be much appreciated.

Cheers,
Martin

2

A good place to start are the camera demos at http://cesiumjs.org/Cesium/Apps/Sandcastle/index.html

3

Thanks, Hyper Sonic, for the reply. I had already looked at the Camera demos, but they all seem to use flyTo() which I want to avoid, because of the "kangaroo jump" effect (see above).

To see in the demo what I mean, first use the "Fly to San Diego" option. Then select "Fly to My Location". Depending on how far that is away from San Diego, you will enroute be lifted to the edge of space before being dropped down again to your destination.

If this is used in a "moving map" type application (with very many very short steps, i.e. position updates), it will result in a very "wobbly" progress.

Cheers,
Martin

4

Fixing camera flights is something we would like to do soon, hopefully right after vector data on terrain is finished (but there’s no set timeframe). It’s actually a pretty hard problem because of the variety of views you may be starting from and finishing at.

Ultimately you can use the Camera API to create your own flight system if you like, but obviously we encourage contributions back to the main code base if someone has a solution they think is worth sharing. The code that actually creates the camera flight in Cesium is at https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Source/Scene/CameraFlightPath.js, so if you want to fiddle with it or implement your own, that would be a good place to start.

5

Thanks, Matthew, good to hear it's at least on the radar.

" It's actually a pretty hard problem because of the variety of views you may be starting from and finishing at."

It seems a bit surprising (but probably only because my Cesium newbie view is too naïve :-)) that it is so difficult.
Wouldn't it be sufficient (at least for basic cases) if the camera "simply"(?) sticks to its initial altitude until told otherwise by the application?
I have so far assumed that the "kangaroo jump" (to the edge of space sometimes) which we currently see (and cannot avoid) between points A and B is merely a feature added "for effect".
Or is it rather a technical necessity of the current camera system?

Anyhow I'll try to dive into the intricacies of the CameraFlightPath code.
Thanks again.

Martin