Hyperbolic Lattice: Poincaré Disk Tessellation

{p,q} tilings • Gaussian curvature K = −1 • hyperbolic geodesics

Tessellation {p, q}

Hyperbolic plane H²
Gaussian K = −1/R²

{p,q} valid iff:
1/p + 1/q < 1/2

Angle deficit per vertex:
π − 2π/p − 2π/q > 0
The Poincaré disk model maps the infinite hyperbolic plane into the unit disk. Straight lines (geodesics) appear as circular arcs meeting the boundary at right angles. Infinite regular tilings {p,q} with 1/p+1/q < 1/2 exist only in hyperbolic space.