Methods and Systems for Generating Continuous Surfaces from Polygonal Data

Abstract

Methods and systems for generating surface data from polygonal data are disclosed. The methods and systems receive polygonal data which describe discrete points on an object. The methods and systems analyze and use the data to calculate and define a continuous BREP object which accurately represents the original polygonal object. In some embodiments, the generated BREP is G2 continuous at substantially all points.

What is claimed is: 
     
         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;   selecting a plurality of the data points;   modifying each of the selected data points by changing the positions of the selected data points to improve continuity of a plurality of regions of the polygonal data, wherein each region includes one of the selected data points;   generating a plurality of continuous curves based on the modified data points, wherein one or more of the continuous curves terminates on at least one of the modified data points;   based at least in part on the continuous curves, generating a plurality of surface boundaries defining one or more continuous surfaces;   generating the BREP data based at least in part on the continuous surfaces; and   storing the BREP data in a computer readable data storage.   
     
     
         2 . The method of  claim 1 , wherein the continuous curves include points of the mesh. 
     
     
         3 . The method of  claim 1 , wherein the continuous curves are G2 continuous. 
     
     
         4 . The method of  claim 1 , wherein the continuous surfaces are G2 continuous. 
     
     
         5 . The method of  claim 1 , wherein the modified data points correspond to points on the surface boundaries. 
     
     
         6 . The method of  claim 1 , further comprising identifying a plurality of data points corresponding to one or more vertices of the polygonal data, the identified data points having a third derivative greater than a threshold, wherein the surface boundaries are generated based at least in part on the identified data points, and wherein the identified data points correspond to points on the surface boundaries. 
     
     
         7 . The method of  claim 1 , wherein generating the continuous curves comprises extending curve segments from the modified data points to adjacent data points. 
     
     
         8 . The method of  claim 7 , wherein at least one of the curve segments is conditionally extended until reaching a second point, the second point being part of another continuous curve. 
     
     
         9 . The method of  claim 7 , wherein a plurality of the curve segments are iteratively extended, such that during each iteration, each of the continuous curves being extended is extended to include an additional point corresponding to a data point of the polygonal data. 
     
     
         10 . The method of  claim 1 , wherein the selected data points are modified to improve continuity of the surface boundaries. 
     
     
         11 . The method of  claim 1 , wherein modifying at least one of the selected data points comprises generating a local surface in the region including the one selected data point and moving the at least one selected data point onto the local surface. 
     
     
         12 . The method of  claim 11 , wherein the local surface is generated based on data points in the region. 
     
     
         13 . The method of  claim 12 , wherein the local surface is generated partly based on the at least one selected data point. 
     
     
         14 . The method of  claim 12 , wherein the at least one selected data point is not used for the generation of the local surface. 
     
     
         15 . The method of  claim 11 , wherein moving the at least one selected data point onto the local surface includes moving the at least one selected data point to a point on the local surface which has a tangent plane normal to a line including the selected data point and the point on the local surface.