fn orbit() -> Vec<Line>Expand description
The orbit and its ticks, as the strokes the line source draws.
The ring is closed by repeating its first station last, and every tick is
its own segment, so no two of them are joined by a stroke. The ring is a
wash — blended over the frame, its ink carrying WASH_ALPHA — and the
ticks are opaque, so one orbit holds both of the source’s ink behaviours.