[Feature] displaying a heatmap on a map within polygons, similar to a height level map

[Algorush]

What problem does this feature solve?

Is there a way to display points as a heatmap on the world map, but not on top of the geoJSON map, as in the example on heatmap-bmap example, but to draw them on the surface of the earth (map polygons) so that the radius and blur do not go beyond the boundaries of the territory. That is, like a height map, perhaps there are already examples with a height map in echarts? It would be great if someone could share or advise how to do this

What does the proposed API look like?

Perhaps it would be possible to draw directly on polygons in renderItem? I'm not very familiar with the API yet