IFC (IFC4X3_ADD2) under development IfcCartesianTransformationOperator

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ABSTRACT This definition may not be instantiated Semantic definition

An IfcCartesianTransformationOperator defines an abstract supertype of different kinds of geometric transformations.

The transformation for a point with position vector P is defined by

P -> A + _S_TP The transformation for a direction d is defined by

d -> Td The transformation for a vector with orientation d and magnitude k is defined by

d -> Td, and k -> Sk For those entities whose attributes include an axis2 placement, the transformation is applied, after the derivation, to the derived attributes p defining the placement coordinate directions. For a transformed surface, the direction of the surface normal at any point is obtained by transforming the normal, at the corresponding point, to the original surface. For geometric entities with attributes (such as the radius of a circle) which have the dimensionality of length, the values will be multiplied by S.

For curves on surface the p curve.reference to curve will be unaffected by any transformation. The Cartesian transformation operator shall only be applied to geometry defined in a consistent system of units with the same units on each axis. With all optional attributes omitted, the transformation defaults to the identity transformation. The Cartesian transformation operator shall only be instantiated as one of its subtypes. Entity inheritance 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.

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.

Click to show 2 hidden inherited attributes Click to hide 2 inherited attributes
IfcCartesianTransformationOperator (6)
1 Axis1 OPTIONAL IfcDirection

The direction used to determine U[1], the derived X axis direction.

2 Axis2 OPTIONAL IfcDirection

The direction used to determine U[2], the derived Y axis direction.

3 LocalOrigin IfcCartesianPoint

The required translation, specified as a cartesian point. The actual translation included in the transformation is from the geometric origin to the local origin.

4 Scale OPTIONAL IfcReal

The scaling value specified for the transformation.

* Scl IfcReal

This attribute is formally derived.

NVL(Scale, 1.0)

The derived scale S of the transformation, equal to scale if that exists, or 1.0 otherwise.

* Dim IfcDimensionCount

This attribute is formally derived.


The space dimensionality of this class, determined by the space dimensionality of the local origin.

Table Formal propositions

Name Description

The derived scaling Scl shall be greater than zero.

Scl > 0.0
Table Formal representation

ENTITY IfcCartesianTransformationOperator
 SUBTYPE OF (IfcGeometricRepresentationItem);
	Axis1 : OPTIONAL IfcDirection;
	Axis2 : OPTIONAL IfcDirection;
	LocalOrigin : IfcCartesianPoint;
	Scale : OPTIONAL IfcReal;
	 Scl : IfcReal := NVL(Scale, 1.0);
	 Dim : IfcDimensionCount := LocalOrigin.Dim;
	ScaleGreaterZero : Scl > 0.0;
END_ENTITY; References

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Is this page difficult to understand? Let us know! Changelog IFC4

  • where rule, ScaleGreaterZero
  • where rule, WR1
  • attribute Scale type, Changed from "real" to "IfcReal"