Dimension analysis of drawings

• US 4,951,227 A
• Filed: 09/30/1988
• Issued: 08/21/1990
• Est. Priority Date: 09/30/1988
• Status: Expired due to Term

• Current Assignee: Saltire Software, Inc.
• Original Assignee: Tektronix Incorporated (Fortive Corp.)
• Inventors: Todd, Philip H.
• Primary Examiner(s): Harkcom, Gary V.
• Assistant Examiner(s): JAFFE, MICHAEL
• Application Number:
  US07/251,270
• Time in Patent Office: 690 Days
• Field of Search: 364/518, 364/520, 364/521, 364/522, 364/523, 364/560, 364/562, 364/518, 364/520, 364/522, 364/523, 364/560, 364/562
• US Class Current: 345/660
• CPC Class Codes: G06T 11/203 Drawing of straight lines or curves

Abstract

Dimensioned sketches are analyzed using graph theoretical concepts to determine whether dimension constraints are sufficient to define unique geometry and are nonredundant.

Claims

1. A computer-aided method of dimension analysis of a geometric figure comprising the following steps:

specifying to a computer a topologic definition of said geometric figure to establish a set of geometric entities interrelated by structure constraints, said structure constraints associating pairs of said geometric entities;

specifying to the computer a dimension definition of said geometric figure to establish stated dimension constraints interrelating selected ones of said geometric entities, said dimension constraints associating pairs of said geometric entities;

determining whether said topologic definition includes a geometric entity constrained by a predetermined number of associated constraints, and, if so,

removing such geometric entity and said predetermined number of associated constraints from said topologic definition and said dimension definition.

2. The method according to claim 1, wherein said geometric figure is a two dimensional geometric figure, said predetermined number of associated constraints is two associated constraints, and subsequent to removal of a geometric entity and its associated constraints from said topologic definition and said dimension definition the method comprises the further steps:

repeatedly determining whether said topologic definition and said dimension definition include a geometric entity constrained by two associated constraints and removing such geometric entity and associated constraints from said topologic definition and said dimension definition until there are no further geometric entities constrained by two associated constraints; and

determining whether the remaining topologic definition and dimension definition consists of two geometric entities interrelated by a single constraint.

3. The method according to claim 1, wherein said topologic definition and said dimension definition are embodied in a data structure having entities corresponding to geometric entities and components of said entities corresponding to structure and dimension constraints.

4. A computer-aided method of dimension analysis of a geometric figure comprising the following steps:

(a) specifying to a computer a topologic definition of said geometric figure to establish a set of geometric entities interrelated by structure constraints;

(b) specifying to a computer a dimension definition of said geometric figure to establish stated dimension constraints applied to and interrelating selected ones of said geometric entities; and

(c) employing the computer to;

(i) model said geometric figure as a graph wherein each vertex corresponds to one of said geometric entities and each edge correspond to a structure constraint or a dimension constraint;

(ii) determine whether said said graph includes a vertex of a given degree, and, if so,

(iii) modify said graph by removing said vertex of a given degree and edges connected thereto.

5. The method according to claim 4, wherein said geometric figure is a two dimensional geometric figure, said given degree is degree two, and step (c) of the method further comprises:

(iv) repeating steps (c) (ii) and (c) (iii) until no further vertices of degree two remain in the graph.

6. The method according to claim 5, wherein said geometric figure is a two dimensional geometric figure and the method further comprises the steps of:

(d) employing the computer to classify said geometric figure as maximally consistent if the result of step (c) (iv) is a single edge connecting two vertices, and otherwise;

(e)

(i) determining whether the modified graph includes a vertex of degree less than two, and, if so,

(iii) modifying the graph by removing the vertex of degree less than two from the graph, and

(f) employing the computer to classify said geometric figure as consistently dimensioned if the modified graph is a null graph and otherwise classify said geometric figure as overdimensioned.

7. The method according to claim 6, wherein step (e) further comprises:

(v) determining whether the modified graph includes a vertex of degree two or less, and if so, modifying the graph by removing the vertex of degree two or less from the graph, and

(vi) repeating step (e) (v) until no further vertices of degree two or less remain.

8. A computer-aided method of generating a scale drawing of a geometric figure comprising the steps:

specifying to a computer a set of geometric entities and structure constraints therebetween to form a topologic definition of said geometric figure, said structure constraints associating pairs of said geometric entities;

specifying to the computer dimension constraints on said geometric entities to form a dimension definition of said geometric figure, said dimension constraints associating pairs of said geometric entities;

employ the computer to modify said topologic definition and said dimension definition by removing geometric entities associated with a given number of constraints and their associated constraints from said topologic definition and said dimension definition until said topologic definition and said dimension definition contain no geometric entities associated with said given number of constraints, said topologic definition then comprising a reduced topologic definition and said dimension definition then comprising a reduced dimension definition;

maintaining in the computer a sequence of geometric operations by storing each geometric entity and its associated constraints when removed from said topologic definition and said dimension definition as a geometric operation wherein the position of each removed geometric entity is specified relative to the remaining topologic definition and dimension definition by means of its associated constraints;

employing the computer to draw on an imaging device a first portion of said scale drawing based upon said reduced topologic definition and said reduced dimension definition; and

employing the computer to draw on said imaging device the remaining portion of said scale drawing by taking said first portion as a reference and utilizing said sequence of geometric operations to construct additional geometric entities relative thereto.