MIXED SHEET EXTENSION

A computer-implemented method of extending a mixed sheet within a B-rep model is described. The mixed sheet includes surfaces having different geometries, such as a mesh positioned between first and second classical geometry surfaces. A first guide curve is defined, located at the boundary of a first surface for a length corresponding to the desired mixed sheet extension adjacent the first surface. A second guide curve may also be defined, located at the boundary of a second surface for a length corresponding to the desired mixed sheet extension adjacent the second surface. At least one extension mesh rung is created by generating facets between the two external mesh vertices using first and second extension vectors, wherein the first extension vector has a pre-determined spatial relationship to the first guide curve. If included, the second extension vector has a pre-determined spatial relationship to the second guide curve.