Splitting a rectangular image to polygons to simulate Breaking glass

I am working on some C# code in which I would like to take a 2D rectangle and split it to smaller 2D polygons. I would like the effect to look like the rectangle was made of glass and it was hit with a hammer in a random spot. I was wondering if anyone knows of a good algorithm to help me with this. I have tried the FortuneVoronoi code using random points to simulate this effect but am having a hard time turning the finished VoronoiGraph in to a set of non intersecting polygons in a reasonable amount of CPU time.