A Voronoi diagram partitions space into cells, one per "seed" point, where every location inside a cell is closer to that cell's seed than to any other seed. Glass fracture simulations scatter seed points across a pane and use these cells as shard boundaries because real cracks in brittle materials also branch and settle into irregular, roughly convex polygonal regions as stress relieves at each fracture front. This makes Voronoi tessellation a cheap but visually convincing stand-in for true fracture mechanics, and it is the technique behind most real-time destruction seen in games and VFX. The pattern is named after the Ukrainian mathematician Georgy Voronoy, who formalized it in 1908, though similar constructions were studied earlier by Dirichlet and Descartes.
Characteristics

• Tempered glass shatters into small, rounded, low-injury-risk pieces ("dicing")
• Annealed (untempered) glass breaks into large, sharp, jagged shards
• Cracks can propagate through glass at speeds up to roughly 1500 m/s
• Voronoi seed/cell count directly controls shard granularity — more seeds, smaller shards
• Impact energy (impulse) controls how far and fast fragments scatter after fracture
• Fracture toolkits in Pixar's Houdini, Blender, and Unreal/Unity destruction plugins use Voronoi cells
• Real fracture mechanics follows stress-concentration and crack-propagation laws this simulation approximates
• Increasing cell count raises polygon count and computation cost roughly linearly