Trim Surface BoundaryKeyCreator \ Modify \ Surface \ Trim-Surface-Boundary
Surface Boundary trimming builds Procedural Trimmed Surfaces. The term Procedural Trimmed Surface means that the resultant surface becomes an elaborate data structure holding the trimming curves plus the original surface. The trimmed surface data struc ture becomes procedurally evaluated by other rou tines which need to access the trimmed surface defin ition, e.g. shading, IGES, polygon displays, flow curve grids, etc.
Complex boundary conditions and internal features, like holes and cut-out patterns, have always caused problems for standard surface equations because there is no place in the surface definition to hold these complex condi tions. It is difficult to define a surface using the standard rectangular array of patches that can describe holes in the interior, or has boundaries more complex than the surface itself.
The solution is to add these troublesome features to the data structure for the trimmed surface, and design special evaluators to look at the trimmed surface data structure differently from a standard surface.
Procedural trimming is accomplished using a simple and intuitive method of trimming a surface to another entity. The trimming entity can be an intersecting surface, or an unbounded plane, or a projectable set of curves lying on or above the surface.
Using the Function: