Process for graphically representing a structure

An apparatus for graphically representing a structure that can be altered by an object, of the type in which both the structure and the object as well as relative movements therebetween are represented by selected respective data structures, the apparatus comprising:

• means for generating a set of polygons representative of the structure from the respective data structure;
• means for determining a processing region corresponding to the object and the selected relative movement between the object and the structure;
• means for determining intersections between the processing region and only those polygons which overlap the processing region and altering the respective data structure to reflect changes to those polygons intersected by the processing region in order to represent the altered structure;
• and
• means for displaying a representation of the respective data structures.

An apparatus for graphically representing a workpiece to be processed by a numerically controlled machine tool, wherein the workpiece and tool are movable relatively to one another along a path, the apparatus comprising:

• means for storing data representative of the shape of the workpiece, the shape of the tool, and the path of relative movement of the tool and the workpiece;
• means for determining boundary polygons representative of the workpiece surface with the aid of the stored data;
• means for hierarchically ordering the boundary polygons;
• means for selecting a surface of the workpiece based upon the path of the tool;
• means for altering the boundary polygons by successive intersection point calculations in correspondence with a path of the tool such that only those intersection points with the boundary polygons that are hierarchically contained in the selected surface are used in the calculations;
• and
• means for displaying the workpiece and alterations to the workpiece as determined from the boundary polygons and from the altered boundary polygons.