A graphics display terminal performs a pan operation with respect to a view motion center to effectuate spherical panning, thereby providing perspective and non-perspective views. Three dimensional instructions stored in terminal memory are re-transformed in accordance with a panned direction. Also a zoom feature is provided so that displayed images may be magnified as desired.

For reliably and easily judging whether or not a cutting locus is correct, which locus has been set in a cutting locus or tool path control program, which program has a step of commanding the rotational angle of a rotary table carrying a workpiece and a step of commanding the locus of a cutter corresponding to each rotational angle commanding step. A rotational angle range for displaying the locus of the cutter is set through a keyboard or the like. A CPU causes a display only if the locus of the cutter is within the set range.

A method for generating an accurate perspective drawing of an object as it would appear from a freely chosen viewpoint, utilizing only data from conventional plan and elevation drawings, arranged according to a prescribed way. This permits an architect or engineer to obtain one or more perspective views of a project which is in the design stage, using only the elevation and plan drawings, which are required anyway. Its practical application is to use a personal computer to carry out the steps of the process, especially if this method is integrated into an existing 2D CAD system. The geometrical and mathematical steps are such that anyone familiar with the software of such a system can provide a suitable routine to enable a user to employ the method. This method allows a change of viewpoint to be made, by simply entering information defining the new viewpoint. A unique additional feature of this invention permits plotting of the elevations upon a cardboard strip, which can be folded into a physical model of the object's selected surfaces. The original data is retained unchanged, so that the conventional plan and elevation views can be plotted at any later time.

A computer system is introduced for curve-solid classification (raycasting) of objects in constructive solid geometry (CSG) modeling to produce image representations of two- or three-dimensional objects. The system carries out curve-solid classifications in parallel and at much higher speed than a general purpose computer. It uses primitive classification processors which compute all of the (curve-line or ray) primitive (basic solid bodies: block, cylinder, etc.) intersections in parallel, combine processors which are connected into a binary tree that duplicates the binary tree defining the CSG solid and computes the set operations (union, intersection and difference), and a host computer.

Automatic layout planning without previously specifying place of each parts is made possible by utilizing groups of rules each comprising a condition section and a procedure section. An appropriate group of rules can be called from a knowledge base according to an intermediate layout plan generated in a data structure by a rule interpreter.