The hole in India:
KML has three parameters for controlling the behaviour of polygons; extrude, tessellate and altitudeMode. By setting altitudeMode to clampToGround, my country polygons follow the great circle and get a solid fill. The problem arises when I extrude the polygons by adding an altitude representing a statistical value. Only the vertices of the polygon are extruded to the given altitude, and not the centre of geometry. I miss a clampToAltitude option in KML. A shape should follow earth’s profile, at the requested height above the surface.
There are some workaround to this problem:
- Give all polygons a minimum altitude to support a "flat roof". Has to be a high value for a country like Russia.
- Break up large polygons into smaller pieces.
- Add additional clampToGround polygons to "hide" the holes. Only works with solid fills (no transparency).