IfcOrientedEdge

标签：Orientation EdgeEnd EdgeStart edge EdgeElement IfcOrientedEdge orientation

IfcOrientedEdge

实体定义

注：定义依据ISO/CD 10303-42:1992

定向边是由另一条边构造的边，它包含BOOLEAN方向标志，用于指示构造的边的方向是否与原始边的方向一致。除了方向之外，定向的边与原始边相等。

 

一种常见的做法是，实体建模系统是有一个表示边的“使用”或“遍历”的实体。这个“使用”实体明确地表示了流形实体中的要求，即每个边必须精确地遍历两次，每个方向一次。“使用”功能由面向边子类型的边提供。

注：实体适用于ISO 10303-42中定义的oriented_edge。

IFC2.0中的新实体。

 

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
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

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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标签：Orientation,EdgeEnd,EdgeStart,edge,EdgeElement,IfcOrientedEdge,orientation
From： https://www.cnblogs.com/herd/p/17582451.html