IfcAxis2Placement3D

Semantic definitions at the entity

Entity definition

The IfcAxis2Placement3D provides location and orientations to place items in a three-dimensional space. The attribute Axis defines the Z direction, RefDirection the X direction. The Y direction is derived.

NOTE The RefDirection does not have to be orthogonal to Axis.

If the attribute values for Axis and RefDirection are not given, the placement defaults to P[1] (x-axis) as [1.,0.,0.], P[2] (y-axis) as [0.,1.,0.] and P[3] (z-axis) as [0.,0.,1.].

	Figure 338 illustrates the definition of the IfcAxis2Placement3D within the three-dimensional coordinate system.
Figure 338 — Axis2 placement 3D

NOTE Definition according to ISO/CD 10303-42:1992
The location and orientation in three dimensional space of three mutually perpendicular axes. An axis2_placement_3D is defined in terms of a point (inherited from placement supertype) and two (ideally orthogonal) axes. It can be used to locate and orientate a non axi-symmetric object in space and to define a placement coordinate system. The entity includes a point which forms the origin of the placement coordinate system. Two direction vectors are required to complete the definition of the placement coordinate system. The axis is the placement Z axis direction and the ref_direction is an approximation to the placement X axis direction.

NOTE Entity adapted from axis2_placement_3d defined in ISO10303-42.

HISTORY New entity in IFC1.5.

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
2	Axis	IfcDirection	[0:1]	The exact direction of the local Z Axis.	X
3	RefDirection	IfcDirection	[0:1]	The direction used to determine the direction of the local X Axis. If necessary an adjustment is made to maintain orthogonality to the Axis direction. If Axis and/or RefDirection is omitted, these directions are taken from the geometric coordinate system.	X
	P :=IfcBuildAxes(Axis, RefDirection)	IfcDirection	L[3:3]	The normalized directions of the placement X Axis (P[1]) and the placement Y Axis (P[2]) and the placement Z Axis (P[3]).	X

Formal Propositions

Rule	Description
LocationIs3D	The dimensionality of the placement location shall be 3.
AxisIs3D	The Axis when given should only reference a three-dimensional IfcDirection.
RefDirIs3D	The RefDirection when given should only reference a three-dimensional IfcDirection.
AxisToRefDirPosition	The Axis and RefDirection shall not be parallel or anti-parallel.
AxisAndRefDirProvision	Either both, Axis and RefDirection are not given and therefore defaulted, or both shall be given.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	C
IfcRepresentationItem
	LayerAssignment	IfcPresentationLayerAssignment @AssignedItems	S[0:1]	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.	X
	StyledByItem	IfcStyledItem @Item	S[0:1]	Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.	X
IfcGeometricRepresentationItem
IfcPlacement
1	Location	IfcCartesianPoint	[1:1]	The geometric position of a reference point, such as the center of a circle, of the item to be located.	X
	Dim :=Location.Dim	IfcDimensionCount	[1:1]	The space dimensionality of this class, derived from the dimensionality of the location.	X
IfcAxis2Placement3D
2	Axis	IfcDirection	[0:1]	The exact direction of the local Z Axis.	X
3	RefDirection	IfcDirection	[0:1]	The direction used to determine the direction of the local X Axis. If necessary an adjustment is made to maintain orthogonality to the Axis direction. If Axis and/or RefDirection is omitted, these directions are taken from the geometric coordinate system.	X
	P :=IfcBuildAxes(Axis, RefDirection)	IfcDirection	L[3:3]	The normalized directions of the placement X Axis (P[1]) and the placement Y Axis (P[2]) and the placement Z Axis (P[3]).	X

Formal representations

XSD Specification

 <xs:element name="IfcAxis2Placement3D" type="ifc:IfcAxis2Placement3D" substitutionGroup="ifc:IfcPlacement" nillable="true"/>

 <xs:complexType name="IfcAxis2Placement3D">

  <xs:complexContent>

   <xs:extension base="ifc:IfcPlacement">

    <xs:sequence>

     <xs:element name="Axis" type="ifc:IfcDirection" nillable="true" minOccurs="0"/>

     <xs:element name="RefDirection" type="ifc:IfcDirection" nillable="true" minOccurs="0"/>

    </xs:sequence>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcAxis2Placement3D

 SUBTYPE OF (IfcPlacement);

  Axis : OPTIONAL IfcDirection;

  RefDirection : OPTIONAL IfcDirection;

 DERIVE

  P : LIST [3:3] OF IfcDirection := IfcBuildAxes(Axis, RefDirection);

 WHERE

  LocationIs3D : SELF\IfcPlacement.Location.Dim = 3;
  AxisIs3D : (NOT (EXISTS (Axis))) OR (Axis.Dim = 3);
  RefDirIs3D : (NOT (EXISTS (RefDirection))) OR (RefDirection.Dim = 3);
  AxisToRefDirPosition : (NOT (EXISTS (Axis))) OR (NOT (EXISTS (RefDirection))) OR (IfcCrossProduct(Axis,RefDirection).Magnitude > 0.0);
  AxisAndRefDirProvision : NOT ((EXISTS (Axis)) XOR (EXISTS (RefDirection)));
END_ENTITY;

 EXPRESS-G diagram

	Einfügepunkt mit zwei Achsen - dreidimensionaler Raum (3D)
	Axis2 Placement3 D