Can I render polygon outline on the 'inside' of the geometry.

1. A concise explanation of the problem you’re experiencing.

I am creating 3D country geometries and the borders of countries are on top of each other. I would like to render the outlines on the inside of the country so if two bordering countries are different colors the borders appear next to each other and not on top of each other.

I am actually creating the borders with corridors but perhaps there is some function someone has figured out that can easily work with polygon outline as well as polyline or corridor.

See attached image with border between Europe and Asia.

Have you tried scaling down the polygon for each country slightly to achieve this effect? I’ve used Turf.js (https://turfjs.org/) for taking a set of vertices and applying a transformation like scale.

Let me know if that ends up looking good.