 | Rationale B茅zier-Spline - Oberfl盲che mit Kontrollpunkten |
 | Rational BSpline Surface With Knots |
 | Surfaces Bsplines rationnelles avec n艙uds |
| 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. |
A rational B-spline surface with knots is a piecewise parametric rational surface described in terms of control points, and associated weight values.
The surface is to be interpreted as follows:
σ
NOTE Entity adapted from rational_b_spline_surface in ISO 10303-42.
HISTORY New entity in IFC4.
| # | Attribute | Type | Cardinality | Description | G |
|---|---|---|---|---|---|
| 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 |
| 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 | G |
|---|---|---|---|---|---|
| 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.
IFC2x3 CHANGE The inverse attribute LayerAssignments has been added. IFC4 CHANGE The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed. | 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.
IFC2x3 CHANGE The inverse attribute StyledByItem has been added. | X | |
| IfcGeometricRepresentationItem | |||||
| IfcSurface | |||||
| Dim :=3 | IfcDimensionCount | The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.
IFC4 CHANGE Derived attribute promoted from subtypes. |
X | ||
| IfcBoundedSurface | |||||
| IfcBSplineSurface | |||||
| 1 | UDegree | IfcInteger | Algebraic degree of basis functions in u. | X | |
| 2 | VDegree | IfcInteger | 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 | Indicator of special surface types. | X | |
| 5 | UClosed | IfcLogical | Indication of whether the surface is closed in the u direction; this is for information only. | X | |
| 6 | VClosed | IfcLogical | Indication of whether the surface is closed in the v direction; this is for information only. | X | |
| 7 | SelfIntersect | IfcLogical | Flag to indicate whether, or not, surface is self-intersecting; this is for information only. | X | |
| UUpper :=SIZEOF(ControlPointsList) - 1 | IfcInteger | Upper index on control points in u direction. | X | ||
| VUpper :=SIZEOF(ControlPointsList[1]) - 1 | IfcInteger | 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 | The description of the knot type. | X | |
| KnotVUpper :=SIZEOF(VKnots) | IfcInteger | The number of distinct knots in the v parameter direction. | X | ||
| KnotUUpper :=SIZEOF(UKnots) | IfcInteger | 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 | |
<xs:element name="IfcRationalBSplineSurfaceWithKnots" type="ifc:IfcRationalBSplineSurfaceWithKnots" substitutionGroup="ifc:IfcBSplineSurfaceWithKnots" nillable="true"/>
<xs:complexType name="IfcRationalBSplineSurfaceWithKnots">
<xs:complexContent>
<xs:extension base="ifc:IfcBSplineSurfaceWithKnots">
<xs:sequence>
<xs:element name="WeightsData">
<xs:complexType>
<xs:sequence>
<xs:element ref="ifc:IfcReal-wrapper" minOccurs="4" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute ref="ifc:itemType" fixed="ifc:IfcReal-wrapper"/>
<xs:attribute ref="ifc:cType" fixed="list list"/>
<xs:attribute ref="ifc:arraySize" use="optional"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
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(SELF\IfcBSplineSurface.ControlPointsList))
AND
(SIZEOF(WeightsData[1]) = SIZEOF(SELF\IfcBSplineSurface.ControlPointsList[1]));
WeightValuesGreaterZero : IfcSurfaceWeightsPositive(SELF);
END_ENTITY;
EXPRESS-G diagram
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