My idea is to use a 'simulated glass crack' decal to mimic cracking glass, adding more connecting crack decals with additional damage. After a specific amount of damage, I replace the glass plane with a Single-Surface 'Glass' Reactor (aka Particle System). In its initial state the Glass Reactor has a specific set of Triangle Shards (Particles) arranged to form a single Glass Plane. The particles are then animated to look exploding like Glass debris.