IfcRectangularTrimmedSurface

IfcRectangularTrimmedSurface是一个曲面，它是通过沿参考曲面的参数空间中定义的两对平行曲线将其基本曲面包围而创建的。

注：定义根据ISO/CD 10303-42:1992

修剪曲面是一个简单的有界曲面，其中边界是常数参数线u1=u1，u2=u2，v1=v1和v2=v2。所有这些值应在参考表面的参数范围内。假设了参数范围的循环特性。矩形修剪曲面直接从基础曲面继承其参数化，参数范围从0到| u2-u1 |和0到| v2-v1 |。

注：如果表面在给定的参数方向上闭合，则u2或v2的值可能需要增加循环范围。

例370度相当于10度，对于那些参数形式是用圆函数（正弦和余弦）定义的曲面。

注：实体改编自ISO 10303-42中的矩形切边曲面。

IFC2x中增加的新实体。

非正式提议：

修整表面的区域应在被修整表面的范围内。

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
1	BasisSurface	IfcSurface	[1:1]	Surface being trimmed.	X
2	U1	IfcParameterValue	[1:1]	First u parametric value.	X
3	V1	IfcParameterValue	[1:1]	First v parametric value.	X
4	U2	IfcParameterValue	[1:1]	Second u parametric value.	X
5	V2	IfcParameterValue	[1:1]	Second v parametric value.	X
6	Usense	IfcBoolean	[1:1]	Flag to indicate whether the direction of the first parameter of the trimmed surface agrees with or opposes the sense of u in the basis surface.	X
7	Vsense	IfcBoolean	[1:1]	Flag to indicate whether the direction of the second parameter of the trimmed surface agrees with or opposes the sense of v in the basis surface.	X

Formal Propositions

Rule	Description
U1AndU2Different	U1 and U2 shall have different values.
V1AndV2Different	V1 and V2 shall have different values.
UsenseCompatible	With exception of those surfaces closed in the U parameter, direction Usense shall be compatible with the ordered parameter values for U.
VsenseCompatible	Vsense shall be compatible with the ordered parameter values for V.

 

#	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
IfcBoundedSurface
IfcRectangularTrimmedSurface
1	BasisSurface	IfcSurface	[1:1]	Surface being trimmed.	X
2	U1	IfcParameterValue	[1:1]	First u parametric value.	X
3	V1	IfcParameterValue	[1:1]	First v parametric value.	X
4	U2	IfcParameterValue	[1:1]	Second u parametric value.	X
5	V2	IfcParameterValue	[1:1]	Second v parametric value.	X
6	Usense	IfcBoolean	[1:1]	Flag to indicate whether the direction of the first parameter of the trimmed surface agrees with or opposes the sense of u in the basis surface.	X
7	Vsense	IfcBoolean	[1:1]	Flag to indicate whether the direction of the second parameter of the trimmed surface agrees with or opposes the sense of v in the basis surface.	X

 

EXPRESS Specification

ENTITY IfcRectangularTrimmedSurface
 SUBTYPE OF (IfcBoundedSurface);
  BasisSurface : IfcSurface;
  U1 : IfcParameterValue;
  V1 : IfcParameterValue;
  U2 : IfcParameterValue;
  V2 : IfcParameterValue;
  Usense : IfcBoolean;
  Vsense : IfcBoolean;
 WHERE
  U1AndU2Different : U1 <> U2;
  V1AndV2Different : V1 <> V2;
  UsenseCompatible : (('IFCGEOMETRYRESOURCE.IFCELEMENTARYSURFACE' IN TYPEOF(BasisSurface)) AND (NOT ('IFCGEOMETRYRESOURCE.IFCPLANE' IN TYPEOF(BasisSurface)))) OR ('IFCGEOMETRYRESOURCE.IFCSURFACEOFREVOLUTION' IN TYPEOF(BasisSurface)) OR (Usense = (U2 > U1));
  VsenseCompatible : Vsense = (V2 > V1);
END_ENTITY;