IfcOrientedEdge

IfcOrientedEdge

实体定义

注：根据ISO/IEC 10303-42:1992的定义

定向边缘是从另一边缘构造的边缘，并且包含BOOLEAN方向标志，以指示构造的边缘的方向是否与原始边缘的方向一致。除了可能的方向外，定向边与原始边等效。

 

一种常见的做法是实体建模系统要有一个实体来表示边缘的“使用”或“遍历”。这个“使用”实体明确表示流形实体中的要求，即每条边必须精确地遍历两次，每个方向一次。“使用”功能由面向边缘子类型的边缘提供。

注：根据ISO 10303-42中定义的定向边缘改编的实体。

IFC2.0中的新实体。

 

Formal Propositions

Rule	Description
EdgeElementNotOriented	The edge element shall not be an oriented edge.

 

 

 

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
IfcTopologicalRepresentationItem
IfcEdge
IfcOrientedEdge
3	EdgeElement	IfcEdge	[1:1]	Edge entity used to construct this oriented edge.	X
4	Orientation	IfcBoolean	[1:1]	BOOLEAN, If TRUE the topological orientation as used coincides with the orientation from start vertex to end vertex of the edge element. If FALSE otherwise.	X
	EdgeStart :=IfcBooleanChoose (Orientation, EdgeElement.EdgeStart, EdgeElement.EdgeEnd)	IfcVertex	[1:1]	The start vertex of the oriented edge. It derives from the vertices of the edge element after taking account of the orientation.	X
	EdgeEnd :=IfcBooleanChoose (Orientation, EdgeElement.EdgeEnd, EdgeElement.EdgeStart)	IfcVertex	[1:1]	The end vertex of the oriented edge. It derives from the vertices of the edge element after taking account of the orientation.	X

 

EXPRESS Specification

ENTITY IfcOrientedEdge
 SUBTYPE OF (IfcEdge);
  EdgeElement : IfcEdge;
  Orientation : IfcBoolean;
 DERIVE
  SELF\IfcEdge.EdgeStart : IfcVertex := IfcBooleanChoose (Orientation, EdgeElement.EdgeStart, EdgeElement.EdgeEnd);
  SELF\IfcEdge.EdgeEnd : IfcVertex := IfcBooleanChoose (Orientation, EdgeElement.EdgeEnd, EdgeElement.EdgeStart);
 WHERE
  EdgeElementNotOriented : NOT('IFCTOPOLOGYRESOURCE.IFCORIENTEDEDGE' IN TYPEOF(EdgeElement));
END_ENTITY;

 

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