William K Fitzgerald

US Patent:

43969887, Aug 2, 1983

Filed:

Dec 31, 1980

Appl. No.:

6/221869

Inventors:

William J. Fitzgerald - Ridgefield CT

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 3153

US Classification:

364521

Abstract:

A method and apparatus for determining the X--Y coordinates on the raster of the intersection of two curves one of which is stored in the display system raster refresh buffer. The second curve is generated by a curve generator or some other source of sequential X--Y coordinate data defining the X--Y coordinates on the raster where the second curve would lie. As each X--Y coordinate is generated by curve generator it is translated into a buffer address and the contents of that address in the buffer memory are accessed and a determination is made to see if said first curve exists at that address. If an element of the first curve is found to exist in the buffer store at the generated address location, it is known an intersection point has been found and the appropriate X--Y address is gated from the system to utilization means. According to a further feature of the invention, if a plurality of intersection points are found for two particular curves, averaging means are provided for at least approximating the midpoint of the actual intersection of the two curves and said midpoint address is gated out of the system as the intersection point. A method and means are also provided for determining if two curves have a point of tangency when they exist on two adjacent raster lines but do not actually intersect.

US Patent:

48559393, Aug 8, 1989

Filed:

Sep 11, 1987

Appl. No.:

7/096171

Inventors:

William J. Fitzgerald - Ridgefield CT
Raymond G. Glemser - Center Valley PA

Assignee:

International Business Machines Corp. - Armonk NY

International Classification:

G06F 314

US Classification:

364522

Abstract:

A computer aided drafting (CAD) procedure presents, for a three dimensional (3D) object to be modeled in a general purpose computer, dimensional and tolerance parameters appropriate to changes of view or parameters. The procedure requires but one model, the three dimensional solid model, for producing both dimensioned displays of the model and dimensioned drawings of views of the model. Dogleg extension lines are used to express 3D dimensions without ambiguity. These dogleg extension lines facilitate the presentation of information on paper or on a display screen and permit convenient alteration of presentations of 3D illustrations, with automatic correction of dimension and tolerance presentation. The operator of the CAD system enters dimension and tolerance information on a plan or elevation view, and this information is automatically converted to an appropriately corrected and presented axonometric presentation.

US Patent:

49012525, Feb 13, 1990

Filed:

Sep 24, 1987

Appl. No.:

7/100686

Inventors:

William J. Fitzgerald - Ridgefield CT
Franklin Gracer - Yorktown Heights NY
Robert N. Wolfe - Peekskill NY

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 1562

US Classification:

364522

Abstract:

The lines representing each edge of each face of each object of a model for producing a multiple object image are segmented at line of sight intersections with other lines representing contour edges of visible faces. Each resulting edge line segment is checked against all visible faces to determine which are visible and which are invisible, and information on visibility is stored together with detailed information on each edge line segment for each object. The model is modified by changing the number of component objects and after each change checking the edge line segments for visibility only with respect to the changes associated with the changed component objects. This results in a substantial reduction in the required number of comparisons between segments and faces as compared to prior methods.