Three patches covering a sphere. (a) Orthographic view. ϕ and θ are the azimuthal and polar angles. B and A (C) overlap at ϕ = 0 (ϕ = π), and A and C overlap at ϕ = π/2. The north pole at θ = 0 and the south pole at θ = π are triple overlaps. (b) Top view. Overlapping regions are exaggerated for clarity. Figures are adopted from the supplemental materials in Ref. [7].