System of relational entities for object-oriented computer-aided geometric design

• US 5,856,828 A
• Filed: 05/05/1997
• Issued: 01/05/1999
• Est. Priority Date: 12/19/1991
• Status: Expired due to Term

• Current Assignee: Aerohydro, Inc.
• Original Assignee: Aerohydro, Inc.
• Inventors: Letcher, John S. Jr.
• Primary Examiner(s): HUYNH, BA
• Application Number:
  US08/851,348
• Time in Patent Office: 610 Days
• Field of Search: 345/326, 345/420, 345/441, 345/964, 364/474.2, 364/598, 706/919
• US Class Current: 345/420
• CPC Class Codes: G06T 17/00 Three dimensional [3D] modelling, e.g. data description of 3D objects
• CPC Class Codes: G06T 17/20 Finite element generation, e.g. wire-frame surface description, tesselation
• CPC Class Codes: Y10S 706/919 Designing, planning, programming, CAD, CASE
• CPC Class Codes: Y10S 715/964 CAD or CAM, e.g. interactive design tools

Abstract

Geometric objects including points, lines, curves, surfaces and solids are defined and constructed in a system which retains and utilizes relationships and dependencies between objects in a directed graph (digraph) data structure. The primary advantage is automatic updating of the model, preserving dependencies, when an underlying object is changed. Multiple types of parametric curves and surfaces and multiple levels of dependency are easily supported through a recursive program structure. Difficulties of surface-surface intersection and trimming are largely avoided by provision of novel entities which permit construction of accurate and durable joins between surface objects.

Claims

1. A method of computer aided design of geometric models constructed from a multiplicity of geometric elements such as points, curves and surfaces in a design space of two or more dimensions, said method comprising:

defining and supporting a set of geometric entities for use in constructing said geometric models, each of said geometric entities being an abstract geometric object type that is adapted to be actualized into one or more corresponding geometric objects stored in computer accessible memory, each of said geometric entities comprising data fields and requiring, for its actualization into each of said one or more corresponding geometric objects, filling specified data fields with data items of valid data types, wherein each corresponding geometric object is stored in said computer accessible memory as a corresponding data structure, each of said geometric entities representing a specific procedure for constructing one or more of said geometric objects from the values in said data fields;

said geometric entities including one or more point class entities, one or more curve class entities, and one or more surface class entities,

wherein each of said point class entities is adapted to be actualized into one or more point class objects, each of said point class objects designating a zero-dimensional point in said design space,

wherein each of said curve class entities is adapted to be actualized into one or more curve class objects, each of said curve class objects designating a one-dimensional continuous point set in said design space,

wherein each of said surface class entities is adapted to be actualized into one or more surface class objects, each of said surface class objects designating a two-dimensional continuous point set in said design space;

identifying at least some of said geometric objects by corresponding unique object identifiers;

defining and supporting a plurality of relational entities among said set of geometric entities, each of said relational entities being adapted to be actualized into one or more corresponding relational objects stored in computer accessible memory, each of said relational entities requiring, for its actualization into each of said one or more corresponding relational objects, references to the object identifiers of one or more geometric objects, which references are stored in computer memory in association with the corresponding actualized relational objects thereby establishing a dependency relationship upon the one or more other geometric objects whose object identifiers are referenced by said relational object;

wherein at least one of said relational entities is one of said curve class entities and requires for actualization into a relational curve class object reference to the object identifiers of two or more point class objects;

wherein at least one of said relational entities is one of said surface class entities and requires for actualization into a relational surface class object reference to the object identifiers of two or more geometric objects selected from a group including point class objects and curve class objects.

2. The computer aided design method of claim 1 wherein each relational object is stored in computer accessible memory as a corresponding data structure having one or more object data fields, each of said object data fields being a data field whose valid data type is an object identifier of another geometric object with which that relational object has a dependency relationship.

3. The computer aided design method of claim 1 wherein at least one of said relational entities is another of said surface class entities and requires for actualization into a relational surface class object reference to the object identifiers of any two or more geometric objects selected from a group including point class objects and curve class objects.

4. The computer aided design method of claim 1 wherein the collection of dependency relationships represents a digraph.

5. The computer aided design method of claim 1 wherein said geometric entities include one or more solid class entities and wherein at least one of said relational entities is one of said solid class entities and requires for actualization into a relational solid class object reference to the object identifiers of two or more other objects.