Canvas, D3, and Cesium.

[Darrel]

When I posted a request on how to get pie charts to display overlaid on a Cesium map, I received a suggestion to use Cesium + D3 + Canvases.  I've gotten that working... sort of.  Specifically, I have logic that does this:

foreach ([set of data by zip code]) {

1)  Takes a set of data associated with a given zip code.

2)  Runs it through D3, to create a pie chart, drawn to a canvas element with the class 'pieCanvas'.

3)  Creates a Cesium.Entity, using that position, and using billboard: { image: canvas } to bind the billboard to that canvas.

4)  Adds that Entity to the viewer.

}

Unfortunately, while I *am* getting pie charts to appear...all of them are using the last pie chart written to the canvas.  Am I missing something, or do I need to actually create (n) canvases, one per unique pie chart I'm intending to display?

[Omar Shehata]

This is just because all your billboards are accessing the same canvas element. It automatically updates (which is usually a good thing, so you can keep updating your canvas to update the billboard).

In this case, if you just want to capture a static image to use in the billboard and re-use the canvas to render the next thing, you can try the solution described in this Stackoverflow post.

Here's a Sandcastle example I put together where I draw the numbers 0 through 4 on the same canvas and render them onto different entities. 

I hope this helps! This looks like a pretty interesting application, what sort of data are you visualizing there?