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IfcAxis1Placement

Definition from ISO/CD 10303-42:1992: The direction and location in three dimensional space of a single axis. An axis1_placement (IfcAxis1Placement) is defined in terms of a locating point (inherited from IfcPlacement supertype) and an axis direction: this is either the direction of axis (Axis) or defaults to (0.0,0.0,1.0). The actual direction for the axis placement is given by the derived attribute z (Z).

NOTE Corresponding STEP name: axis1_placement, please refer to ISO/IS 10303-42:1994, p. 28 for the final definition of the formal standard.

HISTORY New class in IFC Release 1.5
ISSUE See issu log for changes made in IFC Release 1.5.1

Illustration:

axis1 placement Definition of the IfcAxis1Placement within the three-dimensional coordinate system.

EXPRESS specification:

ENTITY IfcAxis1Placement
SUBTYPE OF ( IfcPlacement);
Axis  :  OPTIONAL IfcDirection;
DERIVE
Z  :  IfcDirection :=  NVL (IfcNormalise(Axis), IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0,0.0,1.0]));
WHERE
WR1  :  (NOT (EXISTS (Axis))) OR (Axis.Dim = 3);
WR2  :  SELF\IfcPlacement.Location.Dim = 3;
END_ENTITY;

Attribute definitions:

Axis  :  The direction of the local Z axis.
Z  :  The normalized direction of the local Z axis. It is either identical with the Axis value, if given, or it defaults to [0.,0.,1.]

Formal Propositions:

WR1  :  The Axis when given should only reference a three-dimensional IfcDirection.
WR2  :  The Cartesian point defining the Location shall have the dimensionality of 3.

References (2):

Name Type Referred through Express-G
IfcPlacement Entity
Subtype
Diagram 3
IfcSurfaceOfRevolution Entity
Attribute 'AxisPosition'
Diagram 8

Inheritance graph

ENTITY IfcAxis1Placement;
ENTITY IfcRepresentationItem;
ENTITY IfcGeometricRepresentationItem;
ENTITY IfcPlacement;
Location  :  IfcCartesianPoint;
DERIVE
Dim  :  IfcDimensionCount :=  Location.Dim;
ENTITY IfcAxis1Placement;
Axis  :  OPTIONAL IfcDirection;
DERIVE
Z  :  IfcDirection :=  NVL (IfcNormalise(Axis), IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0,0.0,1.0]));
END_ENTITY;