Patent EP0690416A2 successfully refreshed from Google Patents.
EP0690416A2
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EP
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Topology based tolerancing for geometric modeling operations
Assignee: Computervision Corp
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Filing: 1995-06-27
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Granted: —
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Expires: 2015-06-27
Abstract
Abstract The invention relates to a method and apparatus for tracking and modifying the accumulated error and the current operational tolerance of each topological entity in a geometric model of a three dimensional object. Each topological entity has assigned to it a Mintol value and a Maxtol value. Mintol represents the current accumulated error associated with the entity. Maxtol represents the operational tolerance of the entity for future operations. The Mintol value for an entity is set and occasionally adjusted so that it comprises a volume which encompasses all other entities adjacent to the particular entity. With respect to Maxtol, when two entities are within a distance from each other which is less than the sum of the Maxtols of the two entities, the two entities can be combined. Maxtol is adjusted whenever Mintol is adjusted so as to remain larger than Mintol and whenever a new entity is created by the combination of old entities, so as to encompass the Maxtols of the two old entities.
Inventors
- 👤 Gary A. Crocker
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 17:53
CPC Classifications
G; G06; G06T; G06T17/00
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
223 words
A method for displaying a geometric model of a three dimensional object in which the object is represented by a plurality of topological entities in a linked network, characterized by the steps of: assigning a Mintol value to each corresponding topological entity, the Mintol value designating a distance from the topological entity that defines a volume around each corresponding entity, the volume substantially representing accumulated error associated with the corresponding topological entity; assigning a Maxtol value to each topological entity, the Maxtol value designating a distance from the topological entity that defines a volume centered around the entity, the volume substantially representing operational tolerance associated with each corresponding topological entity; joining two topological entities (100) if they are within their combined Maxtol values of each other, wherein a new topological entity is created; assigning to the new topological entity which is created by the joining of the two topological entities a Maxtol value defining a volume which encloses the volumes defined by the Maxtols of the portions of the other two topological entities which were joined (280, 380, 450); and assigning to the new topological entity which is created by the joining of two other topological entities a Mintol value defining a volume which encloses the volumes defined by the Mintol of the portions of the two topological entities which were joined (270,370,450).
Claim 2
Dependent Claim
48 words
The method as set forth in Claim 1 further characterized by the step of reassigning a Maxtol value of at least twice the Mintol value of the new topological entity, if the Maxtol value is not already at least twice the Mintol value of the new topological entity.
Claim 3
Dependent Claim
29 words
The method as set forth in Claim 2 wherein the topological entities are further characterized by being one of a vertex (30), an edge (34) and a face (37).
Claim 4
Dependent Claim
43 words
The method as set forth in Claim 3 wherein an entity which is created other than by the joining of two other entities is further characterized by assigning a Mintol value which represent accuracy of the representation of the entity in the model.
Claim 5
Independent Claim
247 words
An apparatus for creating a geometric model of a three dimensional object in which the object is represented by a plurality of topological entities in a linked network, including means for creating a dataset of topological entities in a linked network, which network defines the model, characterized by: means for assigning a Mintol value to each topological entity, the Mintol value designating a distance from the topological entity that defines a volume around the entity, the volume substantially representing accumulated error associated with each corresponding topological entity, including means for storing the Mintol value in the dataset; means for assigning a Maxtol value to each topological entity, the Maxtol value designating a distance from the topological entity that defines a volume centered around the entity, the volume substantially representing operational tolerance associated with each corresponding topological entity, including means for storing the Maxtol value in the dataset; means for joining two topological entities if they are separated by a distance not greater than their combined Maxtol values, wherein a new topological entity is created; means for assigning to the new topological entity a Maxtol value defining a volume which encloses the volumes defined by the Maxtols of the portions of the two joined topological entities, wherein the Maxtol value is greater than the Mintol value; and means for assigning to the new topological entity a Mintol value defining the volume which encloses the volumes defined by the Mintol of the portions of the two joined topological entities.
Claim 6
Dependent Claim
47 words
The apparatus as set forth in Claim 5 further characterized by means for reassigning a Maxtol value of at least twice the Mintol value of the corresponding topological entity, if the Maxtol value is not already at least twice the Mintol value of the corresponding topological entity.
Claim 7
Dependent Claim
26 words
The apparatus as set forth in Claim 6 wherein the topological entities are further characterized by being any of vertices (30), edges (34) and faces (37).
Claim 8
Dependent Claim
44 words
The apparatus as set forth in Claim 7 wherein a topological entity which is created other than by the joining of two other entities is further characterized by assigning a Mintol value which represents accuracy of the representation of the entity in the model.
Claim 9
Dependent Claim
18 words
The method as set forth in Claim 1 further comprising the step of displaying the created geometric entity.
Claim 10
Dependent Claim
35 words
The apparatus as set forth in Claim 5 wherein the means for assigning the Mintol value to each topological entity is further characterized by an input means for a user to input the Mintol value.
Claim 11
Dependent Claim
35 words
The apparatus as set forth in Claim 5 wherein the means for assigning the Maxtol value to each topological entity is further characterized by an input means for a user to input the Maxtol value.
Claim 12
Independent Claim
122 words
An apparatus in which a three dimensional object is represented by a dataset in terms of a plurality of topological entities, the relationship between the topological entities being defined by a linked network, characterized by the steps of: means for determining from accumulated error associated with each topological entity a Mintol value for each topological entity, including means for storing the Mintol value in the dataset; means for determining from operational tolerance of the topological entity a Maxtol value for the topological entity, including means for storing the Maxtol value in the dataset; and means for joining two entities when the distance between the entities is not greater than the combined Maxtol values of the entities, wherein a new entity is created.
Claim 13
Dependent Claim
60 words
The apparatus as set forth in Claim 12 wherein the means for joining two entities is further characterized by means for assigning to the new entity which was formed by the joining of the two topological entities a Maxtol value which is twice the Mintol value, if the Maxtol value is not already not less than twice the Mintol value.
Claim 14
Dependent Claim
26 words
The apparatus as set forth in Claim 12 wherein the topological entities are further characterized by being one of vertices (30), edges (34) and faces (37).
Claim 15
Dependent Claim
31 words
The apparatus as set forth in Claim 14 wherein the means for joining two topological entities is further characterized by means for determining the type of topological entities which were joined.
Claim 16
Dependent Claim
70 words
The apparatus as set forth in Claim 15 wherein the means for joining two topological entities, is further characterized by means for assigning a Maxtol value (88'') to a first vertex (88) which is not less than a Maxtol value (87'') of an edge (87) joined to a second vertex (86) and enclosing within a Maxtol value (86'') of the second vertex (86) the Maxtol value of the edge (87).
Claim 17
Dependent Claim
57 words
The apparatus as set forth in Claim 15 wherein the means for joining two topological entities, is further characterized by means for assigning a Maxtol value to an edge which is not less than the Maxtol value of a surface joined to the edge and enclosing relevant sides of the Maxtol value of slabs of the surface.
Claim 18
Dependent Claim
51 words
The apparatus as set forth in Claim 12 further characterized by means for assigning a new Maxtol value in the dataset of the new entity created by the joining of the two topological entities which is not less than the value of the combined Maxtol values of the two topological entities.
Claim 19
Dependent Claim
51 words
The apparatus as set forth in Claim 12 further characterized by means for assigning a new Mintol value in the dataset of the new entity created by the joining of the two topological entities which is not less than the value of the combined Mintol values of the two topological entities.
References Cited (Backward Citations)
US4928243A
Cited
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