1. A method of producing BREP data from electronic polygonal data, the method comprising: accessing the polygonal data with a computer, the polygonal data defining a mesh of polygonal data points; generating a plurality of continuous curves based on the polygonal data; identifying a plurality of first data points corresponding to non-valence 4 vertices in the polygonal data; identifying a plurality of second data points corresponding to polygonal data having a third derivative greater than a threshold; based at least in part on the continuous curves, the first data points, and the second data points, generating a plurality of BREP surface boundaries defining one or more continuous BREP surfaces; generating the BREP data based at least in part on the continuous BREP surfaces; generating one or more additional continuous surfaces, each additional surface being generated based on points corresponding to vertices in the polygonal data which are near one of the non-valence 4 vertices corresponding to an identified non-valence 4 data point; improving the continuity of the BREP data using the continuous additional surfaces; and storing the improved BREP data in a computer readable data storage.