Erm.. he wasn't looking for animated breaking glass. :)
Thinking about it. Something I did for glass once didn't involve any special effects (no spherical or cube mapping), I just painted some white squiggles on a texture (with alpha), reduced the overall alpha to 0.2 (or thereabouts) and stretched it over a single pane of glass. Looked really nice surprisingly. The overall effect was that the windows looked like they were a bit dusty but had been cleaned at some time in the past leaving smears.
Thinking about it. Something I did for glass once didn't involve any special effects (no spherical or cube mapping), I just painted some white squiggles on a texture (with alpha), reduced the overall alpha to 0.2 (or thereabouts) and stretched it over a single pane of glass. Looked really nice surprisingly. The overall effect was that the windows looked like they were a bit dusty but had been cleaned at some time in the past leaving smears.