I mocked this up in potatoshop using one of Jimmy’s voronoi tests. This was just to get a feeling of how the voronoi mesh might look with other landscape features added – the worlds will end up having much larger radii than this.
Dusk is the beginning of darkness in the evening, and occurs after twilight, (during which the sky generally remains somewhat bright and blue). Civil dusk is when the earth has rotated enough that the center of the sun is at 6° below the local horizon. This marks the end of the evening civil twilight, the point where artificial illumination is required to read outside. – Wikipedia