make Billboard construction asynchronous if needed

[mickae1]

Feature

Primitive can be made asynchronous, why not label and billboard ? This is very troublesome to render thousands billboard and label and not having a cesium worker to do the job, the main thread is locked as long the billboards is not built.

[ggetz]

Hi @mickae1, this was discussed in #1487. While there is definitely places we could improve billboard performance, billboards and labels do not have the same workflow as other primitives like polygons. Those primitives use workers to create a mesh from the provided geometry information, while there isn't the equivalent in billboards and labels.

I'm going to close this since there's nothing immediately actionable here as far as I understand. Consider continuing the discussion in #1487 if you have more info.