A computer program product and system executing/implementing the same
provides a visual depiction of a three dimensional object upon a display
device. The program converts feature-based data structure of a designated
solid shape to a direct face data structure of the designated solid shape
in a manner to keep a history of the three dimensional object consistent
with a resulting boundary representation component of the three
dimensional object. In converting the feature-based data structure of the
designated solid shape to the direct face data structure, the program (1)
determines what other solid shapes should be included in the D-Shape; (2)
generates a boundary representation for the designated solid shape; (3)
uses a topology-changeable local operation to generate a modified boundary
representation for the designated solid shape; (4) modifies the history of
the three dimensional object; (5) includes the modified boundary
representation for the designated solid shape with the data structure for
the solid shape; and (6) updates at least part of a history of the three
dimensional object. Further, the program product can reconstruct a
feature-based data structure from a direct face data structure (D-Shape).
In one automatic mode of face selection, the reconstruction process grows
a selected face until a recognizable boundary is encountered. The
recognizable boundary can be any one of a blend, direct face solid shape,
extruded shape, or turn shape.