Definition from ISO/CD 10303-42:1992: The location and orientation in two dimensional space of two mutually perpendicular axes. An axis2_placement_2d (IfcAxis2Placement2D) is defined in terms of a point, (inherited from the IfcPlacement supertype), and an axis. It can be used to locate and originate an object in two dimensional space and to define a placement coordinate system. The class includes a point which forms the origin of the placement coordinate system. A direction vector is required to complete the definition of the placement coordinate system. The reference direction defines the placement X axis direction, the placement Y axis is derived from this.
Definition from IAI: If the RefDirection attribute is not given, the placement defaults to P[1] (x-axis) as [1.,0.] and P[2] (y-axis) as [0.,1.].
NOTE Corresponding STEP name: axis2_placement_2d, 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, the IFC Release 1.0 entity IfcPlacement_2D was using two normalized and orthogonal axes. This definition is replaced in IFC Release 1.5 by the STEP definition of axis placement.
ISSUE: See issue log for changes made in IFC Release 1.5.1
Illustration
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Definition of the IfcAxis2Placement2D within the two-dimensional coordinate system. |