IfcAxis1Placement

ifcaxis1位置提供单个轴的位置和方向。

图说明了ifcaxis1在父三维坐标系中的位置的定义。

注：定义根据ISO/CD 10303-42:1992

单轴在三维空间中的方向和位置。axis1_放置是根据定位点（从placement supertype继承）和轴方向定义的：这是轴的方向，或者默认为（0.0,0.0,1.0）。轴放置的实际方向由派生属性z给出。

注：实体改编自ISO10303-42中定义的axis1_位置。

IFC1.5中增加的新实体

Formal Propositions

Rule	Description
AxisIs3D	The Axis when given should only reference a three-dimensional IfcDirection.
LocationIs3D	The Cartesian point defining the Location shall have the dimensionality of 3.

 

#	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
IfcAxis1Placement
2	Axis	IfcDirection	[0:1]	The direction of the local Z axis.	X
	Z :=NVL (IfcNormalise(Axis), IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0,0.0,1.0]))	IfcDirection	[1:1]	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.]	X

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
  AxisIs3D : (NOT (EXISTS (Axis))) OR (Axis.Dim = 3);
  LocationIs3D : SELFIfcPlacement.Location.Dim = 3;
END_ENTITY;