IfcSurfaceOfLinearExtrusion

IfcSurfaceOfLinearExtramption是通过沿向量扫掠曲线导出的曲面。

注：定义根据ISO/CD 10303-42:1992

该曲面是一个简单的扫掠曲面或通过沿给定方向扫掠曲线而得到的广义圆柱体。参数化如下，其中曲线具有参数化λ（u）：

V = ExtrusionAxis

v的参数化范围为-∞<v<∞，而u的参数化范围由曲线参数化定义。

注：实体改编自ISO 10303-42中定义的线性挤压表面。

IFC2x中增加的新实体。

非正式提议：

表面不得自相交

#	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
IfcSurface
	Dim :=3	IfcDimensionCount	[1:1]	The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.	X
IfcSweptSurface
1	SweptCurve	IfcProfileDef	[1:1]	The curve to be swept in defining the surface. The curve is defined as a profile within the position coordinate system.	X
2	Position	IfcAxis2Placement3D	[0:1]	Position coordinate system for the swept surface, provided by a profile definition within the XY plane of the Position coordinates. If not provided, the position of the profile being swept is determined by the object coordinate system. In this case, the swept surface is not repositioned.	X
IfcSurfaceOfLinearExtrusion
3	ExtrudedDirection	IfcDirection	[1:1]	The direction of the extrusion.	X
4	Depth	IfcLengthMeasure	[1:1]	The depth of the extrusion, it determines the parameterization.	X
	ExtrusionAxis :=IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcVector (ExtrudedDirection, Depth)	IfcVector	[1:1]	The extrusion axis defined as vector.	X

 

EXPRESS Specification

ENTITY IfcSurfaceOfLinearExtrusion
 SUBTYPE OF (IfcSweptSurface);
  ExtrudedDirection : IfcDirection;
  Depth : IfcLengthMeasure;
 DERIVE
  ExtrusionAxis : IfcVector := IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcVector (ExtrudedDirection, Depth);
 WHERE
  DepthGreaterZero : Depth > 0.;
END_ENTITY;