#### 8.7.3.2 IfcAxis2Placement3D

| Einfügepunkt mit zwei Achsen - dreidimensionaler Raum (3D)

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 120 illustrates the definition of the IfcAxis2Placement3D within the three-dimensional coordinate system.
Figure 120 — 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.

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;

Attribute Definitions:

Axis | : | The exact direction of the local Z Axis.
RefDirection | : | 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.
P | : | The normalized directions of the placement X Axis (P[1]) and the placement Y Axis (P[2]) and the placement Z Axis (P[3]).

Formal Propositions:

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.

Inheritance Graph:

ENTITY IfcAxis2Placement3D

| ENTITY IfcRepresentationItem

| INVERSE

LayerAssignment | : | SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItems;
StyledByItem | : | SET [0:1] OF IfcStyledItem FOR Item;

| ENTITY IfcGeometricRepresentationItem

| ENTITY IfcPlacement

Location | : | IfcCartesianPoint;

| DERIVE

Dim | : | IfcDimensionCount := Location.Dim;

| ENTITY IfcAxis2Placement3D

Axis | : | OPTIONAL IfcDirection;
RefDirection | : | OPTIONAL IfcDirection;

| DERIVE

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

END_ENTITY;

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