IfcEdgeCurve

标签：curve 曲线 vertex same edge IfcEdgeCurve

IfcEdgeCurve

实体定义

IfcEdgeCurve定义拓扑连接的两个顶点，包括连接的几何表示。

 上图显示了一个示例，其中边几何图形由无界曲线给出，此处为IfcCircle。边界由EdgeStart和EdgeEnd提供，通过SameSense=FALSE，IfcEdgeCurve的拓扑方向与IfcCircle的方向相反。

 

注：定义依据ISO/CD 10303-42:1992

边曲线是边的一种特殊子类型，其几何图形已完全定义。通过将边与可能是无边界的曲线相关联来定义几何体。由于拓扑方向和几何方向可能相反，因此使用指示符（相同意义）来识别边和曲线方向是一致还是相反。布尔值指示曲线方向是与边方向一致（TRUE）还是与边方向相反（FALSE）。与边缘顶点相关的任何几何图形应与边缘几何图形一致。多条边可以参照同一条曲线。

注：实体适用于ISO 10303-42中定义的边缘曲线。

IFC2x中的新实体。

非正式提议：

1. 边曲线的域被正式定义为由顶点修剪的边几何体的域。此域不包括顶点。
2. 边曲线具有非零的有限范围。
3. 边曲线是一个流形。
4. 边曲线是弧形连接的。
5. 边缘起点不是边缘域的一部分。
6. 边端不是边域的一部分。
7. 顶点几何形状应与边缘几何形状一致。

 

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
3	EdgeGeometry	IfcCurve	[1:1]	The curve which defines the shape and spatial location of the edge. This curve may be unbounded and is implicitly trimmed by the vertices of the edge; this defines the edge domain. Multiple edges can reference the same curve.	X
4	SameSense	IfcBoolean	[1:1]	This logical flag indicates whether (TRUE), or not (FALSE) the senses of the edge and the curve defining the edge geometry are the same. The sense of an edge is from the edge start vertex to the edge end vertex; the sense of a curve is in the direction of increasing parameter.	X

 

 

 

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
1	EdgeStart	IfcVertex	[1:1]	Start point (vertex) of the edge.	X
2	EdgeEnd	IfcVertex	[1:1]	End point (vertex) of the edge. The same vertex can be used for both EdgeStart and EdgeEnd.	X
IfcEdgeCurve
3	EdgeGeometry	IfcCurve	[1:1]	The curve which defines the shape and spatial location of the edge. This curve may be unbounded and is implicitly trimmed by the vertices of the edge; this defines the edge domain. Multiple edges can reference the same curve.	X
4	SameSense	IfcBoolean	[1:1]	This logical flag indicates whether (TRUE), or not (FALSE) the senses of the edge and the curve defining the edge geometry are the same. The sense of an edge is from the edge start vertex to the edge end vertex; the sense of a curve is in the direction of increasing parameter.	X

 

 

EXPRESS Specification

ENTITY IfcEdgeCurve
 SUBTYPE OF (IfcEdge);
  EdgeGeometry : IfcCurve;
  SameSense : IfcBoolean;
END_ENTITY;

 

 

 

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标签：curve,曲线,vertex,same,edge,IfcEdgeCurve
From： https://www.cnblogs.com/herd/p/17582383.html