A computer aided design (CAD) system has the capability of operating in either a 2D or a 3D mode. In 2D mode, the system uses only instructions contained in a 2D instruction memory and executes only instructions relating to 2D geometry. Upon receipt of a command relating to 3D geometry, the system performs a 2D to 3D transformation, performs a topolgy check, transfers control to a 3D instruction memory and performs instructions relating to 3D geometry.

A process for graphically representing a simulated workpiece as processed by a numerically-controlled machine tool. Stored data defining the workpiece and the tool as well as program data defining relative movement therebetween are used to generate polygons which represent the workpiece and the tool and the path of movement of the tool. These polygons are hierarchically ordered and liked. Corresponding to the hierarchic order of the polygons, intersection point calculations in the linkage are made only for the workpiece polygons which overlap the tool polygon. The image of the processed workpiece is generated successively through the continuous superposition of the changing workpiece polygons with the processing polygons corresponding to the tool and its path. Workpiece edges which drop out are erased, and invisible workpiece edges are nto represented.

An interactive graphic recognition and data processing system includes an image reader for reading a facility drawing in which facility symbols are drawn, a display device for displaying the facility drawing read by the image reader overlapped with a topographical drawing corresponding thereto, a mouse for designating the position of the facility symbol displayed on the display device, a recognition device for recognizing the facility symbol designated by the mouse by comparing the same with a plurality kinds of facility symbols previously stored and causing the facility symbols recognized thereby to be displayed in different color from the color of the facility symbols which have not yet been recognized, and a memory for storing therein positional data in the topographical drawing of the facility symbol recognized by the recognition device and attributive data about the facility symbol as data base.

A method of generating a two-dimensional (2-D) image of a transform of a three-dimensional (3-D) solid object involves sub-dividing a 3-D box defining viewing space into sub-boxes, generating test-cells in object space by performing an inverse transform on the sub-boxes and determining which of the test-cells intersect the object. Thus, the need to transform the object itself is avoided. A particular application of the method is the generation of 2-D perspective images of a 3-D solid object. A graphics processing system including means for performing the method is defined.

Graphic data of design objects designated by an input device are retrieved from a design object data memory and displayed on a display device. A restrictive item applied to the design object displayed on the display device and redesignated by the input device is read from the design object data memory. Specification data of the designated design objects are also read from the design object data memory. A condition part of the design reference is made based on the redesignated design object and the selected specification data, and an end portion of the design reference is made based on the redesignated design object, the selected restrictive item and a reference value entered by the input device. The design reference including the condition part and the end portion is displayed on the display device and stored into a design reference memory.