Topology based tolerancing for geometric modeling operations

Claim 1

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 5

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 12

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.