| | Provides an efficient method of unioning a collection of IPolygonal geometrys. The geometries are indexed using a spatial index, and unioned recursively in index order. For geometries with a high degree of overlap, this has the effect of reducing the number of vertices early in the process, which increases speed and robustness. This algorithm is faster and more robust than the simple iterated approach of repeatedly unioning each polygon to a result geometry. The buffer(0) trick is sometimes faster, but can be less robust and can sometimes take a long time to complete. This is particularly the case where there is a high degree of overlap between the polygons. In this case, buffer(0) is forced to compute with all line segments from the outset, whereas cascading can eliminate many segments at each stage of processing. The best situation for using buffer(0) is the trivial case where there is no overlap between the input geometries. However, this case is likely rare in practice. More...
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1.8.8 
