Visualizing a mesh-wise quantity

My problem is as follows: I want to visualize a quantity which varies over a domain, but is piecewise constant over subdomains, each of which has its own mesh. I’ve been doing this by saving the value as cell-centered values in a multiblock VTK file but this is much more expensive than necessary. How could I efficiently visualize this quantity (probably using Makie)?

What do you expect from this visualization? Interactivity, handling millions of cells, …

I’d like to be able to record a movie consisting of a few hundreds of frames in a reasonable time. The point is I’d like to represent each domain as a filled polygon with a color mapping to the variable value, but right now I don’t have a better way to handle it than assigning a value to each cell. I’d like to extract the boundary of each subdomain from the mesh as a polygon. The number of subdomains right now is from a few hundred to ~10000.

Kind of like a map? GIS?

The visualization I’m getting at looks something like this

Each of the joints and struts in this picture has ~800 elements so as the scale of this gets larger it becomes quite expensive to plot a cell centered variable. For visualizations like this one, though, the variable I’m interested in is piecewise constant over each of those domains.

Graph visualization? I believe there is a specialized library for that.