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8.9.3.75 IfcVector

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AbV ⓘ

8.9.3.75.1 Semantic definition

An IfcVector is a geometric representation item having both a magnitude and direction. The magnitude of the vector is solely defined by the Magnitude attribute and the direction is solely defined by the Orientation attribute.

The DirectionRatios of the Orientation attribute are not used to define the magnitude. Definition according to ISO/CD 10303-42:1992 The vector is defined in terms of the direction and magnitude of the vector. The value of the magnitude attribute defines the magnitude of the vector. The magnitude of the vector can not be reliable calculated from the components of the orientation attribute. This form of representation was selected to reduce problems with numerical instability. For example a vector of magnitude 2.0 mm and equally inclined to the coordinate axes could be represented with Orientation attribute of (1.0,1.0,1.0). Entity adapted from vector defined in ISO 10303-42. New entity in IFC1.0

8.9.3.75.2 Entity inheritance

8.9.3.75.3 Attributes

# Attribute Type Description
IfcRepresentationItem (2)
LayerAssignment SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItems

Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.

The inverse attribute LayerAssignments has been added. The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.
StyledByItem SET [0:1] OF IfcStyledItem FOR Item

Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.

The inverse attribute StyledByItem has been added.
Click to show 2 hidden inherited attributes Click to hide 2 inherited attributes
IfcVector (3)
1 Orientation IfcDirection

The direction of the vector.
2 Magnitude IfcLengthMeasure

The magnitude of the vector. All vectors of Magnitude 0.0 are regarded as equal in value regardless of the orientation attribute.
* Dim IfcDimensionCount

This attribute is formally derived. 

Orientation.Dim

The space dimensionality of this class, it is derived from Orientation
Table 8.9.3.75.F

8.9.3.75.4 Formal propositions

Name Description
MagGreaterOrEqualZero

The magnitude shall be positive or zero.

 
Magnitude >= 0.0
Table 8.9.3.75.G

8.9.3.75.5 Examples

8.9.3.75.6 Formal representation 

ENTITY IfcVector
 SUBTYPE OF (IfcGeometricRepresentationItem);
	Orientation : IfcDirection;
	Magnitude : IfcLengthMeasure;
 DERIVE
	 Dim : IfcDimensionCount := Orientation.Dim;
 WHERE
	MagGreaterOrEqualZero : Magnitude >= 0.0;
END_ENTITY;

8.9.3.75.7 References

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8.9.3.75.8 Changelog

8.9.3.75.8.1 IFC4

  • where rule, MagGreaterOrEqualZero
  • where rule, WR1