IfcRationalBSplineSurfaceWithKnots

改变的历史记录：

Item	SPF	XML	Change	Description
IFC2x3 to IFC4
IfcRationalBSplineSurfaceWithKnots			ADDED
IFC4 Addendum 1
IfcRationalBSplineSurfaceWithKnots
UDegree			MODIFIED	Type changed from INTEGER to IfcInteger.
VDegree			MODIFIED	Type changed from INTEGER to IfcInteger.
UClosed			MODIFIED	Type changed from LOGICAL to IfcLogical.
VClosed			MODIFIED	Type changed from LOGICAL to IfcLogical.
SelfIntersect			MODIFIED	Type changed from LOGICAL to IfcLogical.
UMultiplicities			MODIFIED	Type changed from INTEGER to IfcInteger.
VMultiplicities			MODIFIED	Type changed from INTEGER to IfcInteger.
WeightsData			MODIFIED	Type changed from REAL to IfcReal.

 

实体定义

带结有理B样条曲面是用控制点和相关的权值描述的分段参数有理曲面。

表面解释如下：

 

注：实体改编自ISO 10303-42中的有理b样条曲面。

 

IFC4中增加的新实体。

 

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
13	WeightsData	IfcReal	L[2:?]L[2:?]	The weights associated with the control points in the rational case.	X
	Weights :=IfcMakeArrayOfArray(WeightsData,0,UUpper,0,VUpper)	IfcReal	A[0:UUpper]A[0:VUpper]	Array (two-dimensional) of weight values constructed from the WeightsData.	X

Formal Propositions

Rule	Description
CorrespondingWeightsDataLists	The array dimensions for the weights shall be consistent with the control points data.
WeightValuesGreaterZero	The weight value associated with each control point shall be greater than zero.

 

#	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
IfcBSplineSurface
1	UDegree	IfcInteger	[1:1]	Algebraic degree of basis functions in u.	X
2	VDegree	IfcInteger	[1:1]	Algebraic degree of basis functions in v.	X
3	ControlPointsList	IfcCartesianPoint	L[2:?]L[2:?]	This is a list of lists of control points.	X
4	SurfaceForm	IfcBSplineSurfaceForm	[1:1]	Indicator of special surface types.	X
5	UClosed	IfcLogical	[1:1]	Indication of whether the surface is closed in the u direction; this is for information only.	X
6	VClosed	IfcLogical	[1:1]	Indication of whether the surface is closed in the v direction; this is for information only.	X
7	SelfIntersect	IfcLogical	[1:1]	Flag to indicate whether, or not, surface is self-intersecting; this is for information only.	X
	UUpper :=SIZEOF(ControlPointsList) - 1	IfcInteger	[1:1]	Upper index on control points in u direction.	X
	VUpper :=SIZEOF(ControlPointsList[1]) - 1	IfcInteger	[1:1]	Upper index on control points in v direction.	X
	ControlPoints :=IfcMakeArrayOfArray(ControlPointsList, 0,UUpper,0,VUpper)	IfcCartesianPoint	A[0:UUpper]A[0:VUpper]	Array (two-dimensional) of control points defining surface geometry. This array is constructed from the control points list.	X
IfcBSplineSurfaceWithKnots
8	UMultiplicities	IfcInteger	L[2:?]	The multiplicities of the knots in the u parameter direction.	X
9	VMultiplicities	IfcInteger	L[2:?]	The multiplicities of the knots in the v parameter direction.	X
10	UKnots	IfcParameterValue	L[2:?]	The list of the distinct knots in the u parameter direction.	X
11	VKnots	IfcParameterValue	L[2:?]	The list of the distinct knots in the v parameter direction.	X
12	KnotSpec	IfcKnotType	[1:1]	The description of the knot type.	X
	KnotVUpper :=SIZEOF(VKnots)	IfcInteger	[1:1]	The number of distinct knots in the v parameter direction.	X
	KnotUUpper :=SIZEOF(UKnots)	IfcInteger	[1:1]	The number of distinct knots in the u parameter direction.	X
IfcRationalBSplineSurfaceWithKnots
13	WeightsData	IfcReal	L[2:?]L[2:?]	The weights associated with the control points in the rational case.	X
	Weights :=IfcMakeArrayOfArray(WeightsData,0,UUpper,0,VUpper)	IfcReal	A[0:UUpper]A[0:VUpper]	Array (two-dimensional) of weight values constructed from the WeightsData.	X

 

EXPRESS Specification

ENTITY IfcRationalBSplineSurfaceWithKnots
 SUBTYPE OF (IfcBSplineSurfaceWithKnots);
  WeightsData : LIST [2:?] OF LIST [2:?] OF IfcReal;
 DERIVE
  Weights : ARRAY [0:UUpper] OF ARRAY [0:VUpper] OF IfcReal := IfcMakeArrayOfArray(WeightsData,0,UUpper,0,VUpper);
 WHERE
  CorrespondingWeightsDataLists : (SIZEOF(WeightsData) = SIZEOF(SELFIfcBSplineSurface.ControlPointsList)) AND (SIZEOF(WeightsData[1]) = SIZEOF(SELFIfcBSplineSurface.ControlPointsList[1]));
  WeightValuesGreaterZero : IfcSurfaceWeightsPositive(SELF);
END_ENTITY;