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IfcGeometricRepresentationContext

Definition from ISO/CD 10303-42:1992: A geometric representation context is a representation context in which the geometric representation items are geometrically founded. A geometric representation context is a distinct coordinate space, spatially unrelated to other coordinate spaces.

Definition from IAI: The IfcGeometricRepresentationContext defines the context that applies to several shape representations of a product. It defines the type of the context in which the shape representation is defined, that can be used to describe the level of detailing for which the shape representation is valid (inherited from the supertype), and the numeric precision applicable to the geometric representation items defined in this context.

NOTE: The definition of this class relates to the STEP entity geometric_representation_context. Please refer to ISO/IS 10303-42:1994 for the final definition of the formal standard.
ISSUE: See issue and change log for changes made in IFC Release 1.5 and IFC 2x.
HISTORY: New Entity in IFC Release 2.0

EXPRESS specification:

ENTITY IfcGeometricRepresentationContext
SUBTYPE OF ( IfcRepresentationContext);
CoordinateSpaceDimension  :  IfcDimensionCount;
Precision  :  OPTIONAL REAL;
WorldCoordinateSystem  :  IfcAxis2Placement;
TrueNorth  :  OPTIONAL IfcDirection;
WHERE
WR1  :  CoordinateSpaceDimension = WorldCoordinateSystem.Dim;
END_ENTITY;

Attribute definitions:

CoordinateSpaceDimension  :  The integer dimension count of the coordinate space modeled in a geometric representation context.
Precision  :  Value of the model precision for geometric models. It is a double value (REAL), typically in 1E-5 to 1E-8 range, that indicates the tolerance under which two given points are still assumed to be identical. The value can be used e.g. to sets the maximum distance from an edge curve to the underlying face surface in brep models.
WorldCoordinateSystem  :  Establishment of the world coordinate system for the representation context used by the project.
TrueNorth  :  Direction of the true north relative to the world coordinate system as established by the representation context.

Formal Propositions:

WR1  :  The attribute CoordinateSpaceDimension should comply with the dimensionality of the WorldCoordinateSystem.

References (1):

Name Type Referred through Express-G
IfcRepresentationContext Entity
Subtype
Diagram 1

Inheritance graph

ENTITY IfcGeometricRepresentationContext;
ENTITY IfcRepresentationContext;
ContextIdentifier  :  OPTIONAL IfcLabel;
ContextType  :  OPTIONAL IfcLabel;
INVERSE
RepresentationsInContext  :  SET OF IfcRepresentation FOR ContextOfItems;
ENTITY IfcGeometricRepresentationContext;
CoordinateSpaceDimension  :  IfcDimensionCount;
Precision  :  OPTIONAL REAL;
WorldCoordinateSystem  :  IfcAxis2Placement;
TrueNorth  :  OPTIONAL IfcDirection;
END_ENTITY;