An approach for processing irregular data into the regular data in reverse engineering

One of the most difficult problems in reverse engineering is the processing of irregular data. The popular surfaces modelling tools such as NURBS surfaces that are defined on a four-sided domain cannot be directly created from irregular data. Therefore, in reverse engineering, it is necessary to process irregular data into the regular data that has the form of a regular four-sided net for creating NURBS surfaces from the regular data. An approach for processing irregular data into the regular data is presented in this paper. First, an initial 3D triangulation is constructed from irregular data through projecting 3D irregular data onto a corresponding plane to generate 2D irregular data and triangulating the 2D irregular data by an improved 2D triangulation algorithm. Second, the initial triangulation is further optimized in 3D space to ensure that the surfaces created From the optimized spatial triangulation have the better form. The optimization is to make most of the triangles in the initial 3D triangulation have the same convexity or concavity as that of the physical surface. Third, five-degree triangular surfaces with C-1 continuity are constructed by interpolating each triangle in the spatial triangulation. Fourth, a series of section-data can be obtained by cutting the triangular surfaces with a series of parallel planes. Last, the regular data is obtained by deleting repeated data points in each section-data, smoothing and uniforming each section-data. This approach has been applied to the reverse engineering in an aircraft manufacturing company, and has met with a preliminary success.