IFC 4.3.x development

8.9.3.30 IfcDirection

Change log

IFC4

additions where_rules MagnitudeGreaterZero
modificationsattributes DirectionRatios definitionChanged from list[2:3] of real to list[2:3] of IfcReal

8.9.3.30.1 Semantic definitions at the entity

The IfcDirection provides a direction in two or three dimensional space depending on the number of DirectionRatio's provided. The IfcDirection does not imply a vector length, and the direction ratios does not have to be normalized.

NOTE  Definition according to ISO/CD 10303-42:1992
This entity defines a general direction vector in two or three dimensional space. The actual magnitudes of the components have no effect upon the direction being defined, only the ratios X:Y:Z or X:Y are significant.

NOTE  The components of this entity are not normalized. If a unit vector is required it should be normalized before use.

NOTE  Entity adapted from direction defined in ISO 10303-42.

HISTORY  New entity in IFC1.0

8.9.3.30.1 Attributes

# Attribute Type Description
IfcRepresentationItem
LayerAssignmentSET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItemsAssignment 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.

> IFC2x3 CHANGE  The inverse attribute LayerAssignments has been added.

> IFC4 CHANGE  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.



> IFC2x3 CHANGE  The inverse attribute StyledByItem has been added.
IfcGeometricRepresentationItem
IfcDirection
1 DirectionRatiosLIST [2:3] OF IfcReal The components in the direction of X axis (DirectionRatios[1]), of Y axis (DirectionRatios[2]), and of Z axis (DirectionRatios[3])
Dim INVALID The space dimensionality of this class, defined by the number of real in the list of DirectionRatios.

8.9.3.30.2 Entity inheritance

dot_inheritance IfcDirection IfcDirection IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcDirection->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem

8.9.3.30.3 Formal representations

ENTITY IfcDirection
 SUBTYPE OF (IfcGeometricRepresentationItem);
	DirectionRatios : LIST [2:3] OF IfcReal;
 DERIVE
	 Dim : IfcDimensionCount := HIINDEX(DirectionRatios);
 WHERE
	MagnitudeGreaterZero : SIZEOF(QUERY(Tmp <* DirectionRatios | Tmp <> 0.0)) > 0;
END_ENTITY;