2D Cutting Stock Problem for Glass - Details mentioned
It sounds like your glass cutting problem is exactly like the 2D guillotine stock cutting problem -- am I correct that there is no difference?

I think Macleod et al's O(n^3) approximation algorithm from the 1990s is still the best known result with proven optimality bounds for very large instances of this problem, but for only 100-200 pieces the exact algorithm by Christofides and Hadjiconstantinou should be able to find the optimal solution in reasonable time.  There are also good heuristics for this problem via dynamic programming.

A survey on software solvers for the cutting stock problem was written by Macedo et al here in case you're looking for practical solutions.