Čech Nerve & Topology

Cover a point cloud with balls — watch the nerve simplicial complex reveal topology

Controls

Čech Homology (approx.)
H₀ (components):
H₁ (loops):
Vertices |V|:
Edges |E|:
Triangles |T|:
χ = V-E+T:
The nerve of a cover {U_α} has:
• Vertex per set U_α
• Edge if U_α ∩ U_β ≠ ∅
• Triangle if U_α ∩ U_β ∩ U_γ ≠ ∅

Nerve theorem: If cover is good (all intersections contractible), nerve ≃ union of sets.

Vary r to see topology change at critical radii.