Support for animated billboards

[mramato]

Animated billboards has come up numerous times on the mailing list, most recently here: https://groups.google.com/d/msg/cesium-dev/Qd_LRhmlb50/j-_rdsVUK4IJ I don't expect this to happen anytime soon, but since we didn't have an issue for it; I figured I'd create one.

Me and @shunter have some ideas on how to do this within the existing BillboardCollection architecture, it would basically involve an internal list of images/canvases/etc.. that need to be re-uploaded to the same spot in the text coordinates each frame. There's a chance that the ultimate answer is we need something other than a Billboard to do this, but it seems like a reasonable extension of the existing primitive.

EDIT: Better thread with use case: https://groups.google.com/d/msg/cesium-dev/cF9Vt28Wk-4/nJ68p3YONKcJ

[shunter]

Another thought I've had is that it might be reasonable to make the private TextureAtlas use reference counting, so essentially when a billboard changes its image, it would release its ref to the previous location, which could allow that location in the atlas to be reused for new textures.

[mramato]

Makes sense. We could also compact the atlas every so often if there are lots of unused textures. This way if someone is dynamically drawing with a canvas, it throws away old snapshots.

[shunter]

Yes, although you get re-use for "free" without compacting if you release the old ref before adding the new one, because it will re-use that location immediately (assuming the same size, and that no other billboard in the collection has a ref to the old snapshot)

[pjcozzi]

Related forum discussion: https://groups.google.com/forum/#!topic/cesium-dev/JzpfPUvBdEA

[hpinkos]

Support for dynamic billboards has been requested on the forum a number of times:

https://groups.google.com/d/msg/cesium-dev/jFsmh7LOiTs/MCJfLJlEZZgJ
https://groups.google.com/d/msg/cesium-dev/cF9Vt28Wk-4/nJ68p3YONKcJ
https://groups.google.com/d/msg/cesium-dev/tuQyixSKJuA/3-jsFmIABwAJ
https://groups.google.com/d/msg/cesium-dev/Sd4x1YmneCs/nfMsP3eaAwAJ
https://groups.google.com/d/msg/cesium-dev/JzpfPUvBdEA/8adq-uKfb7sJ

[ggetz]

Requested on the forum: https://groups.google.com/forum/#!topic/cesium-dev/ah039dU-4No

[mramato]

I have an old implementation of this which uses animated gifs (but really as long as you have the frames it works). It's an Entity API-level solution, but that kind of makes the most sense anyway. I'll see if I can dig up the code and post it here, might be a good PR for someone else to finish up if I can't find the time.

[ggetz]

@mramato Do you have your gif implementation still? It was requested on the forum: https://groups.google.com/forum/#!topic/cesium-dev/Qd_LRhmlb50

[mramato]

it's the animated-billboards branch, but it's really just one new file in a helper class called BillboardAnimator that you can see here: https://github.com/AnalyticalGraphicsInc/cesium/compare/animated-billboards

It's been a while, but I think you use it like this:

var animator = BillboardAnimator.fromGif({url: url});
entity.billboard.image = animator.image;
entity.billboard.imageSubRegion = animator.imageSubRegion

As you can tell, I never finished it so the usability is a little quirky, but it works really well. Here's a live demo http://mramato.github.io/Demos/AnimatedBillboards/index.html (the imagery doesn't load because ancient version of Cesium)

[OmarShehata]

Requested again: https://groups.google.com/d/msg/cesium-dev/XQoDWp02Ysk/JAM5fABtCQAJ

[OmarShehata]

Requested again: https://groups.google.com/d/msg/cesium-dev/j6EVJ2e_nzg/Sk6BWJ7ICwAJ

[TannerBragg]

We definitely have a need for this feature. I work on an app that is fed a CZML data source with real time data. We feed SVG Data URI to billboards to track objects. The data uri is generated using https://spatialillusions.com/milsymbol/ library. I should also clarify the data uri is generated by a nodejs service on the back end which is then kicked up to the front end in a CZML data stream. I can break cesium in as little as two minutes with a small set of our data. :( The edit forum thread on the OP describes our problem exactly.

Finally, when we update the entity's billboard with a new data uri, we are left with an unpleasant flickering/flashing of the image when the new image is loaded. It would be very nice if there was a double buffering feature where the image appeared to "move" when updated and redrawn.

[markerikson]

I wrote the second Groups thread, 5 years ago. Still working on the same app, with the same workaround in place. This would be extremely beneficial to have.

[ggetz]

In #11569, @syzdev noted jitters that can occur with larger images when updating subregions of billboards.