 | Bézier-Spline-Kurve mit (gegebenen) Kontrollpunkten |
 | BSpline Curve With Knots |
| Item | SPF | XML | Change | Description | IFC2x3 to IFC4 |
|---|---|---|---|---|
| IfcBSplineCurveWithKnots | ADDED | IFC4 Addendum 1 | ||
| IfcBSplineCurveWithKnots | ||||
| Degree | MODIFIED | Type changed from INTEGER to IfcInteger. | ||
| ClosedCurve | MODIFIED | Type changed from LOGICAL to IfcLogical. | ||
| SelfIntersect | MODIFIED | Type changed from LOGICAL to IfcLogical. | ||
| KnotMultiplicities | MODIFIED | Type changed from INTEGER to IfcInteger. | IFC4x2 FINAL | |
| IfcBSplineCurveWithKnots | ||||
| PositioningElement | ADDED |
The IfcBSplineCurveWithKnots is a spline curve parameterized by spline functions for which the knot values are explicitly given.
NOTE Definition according to ISO/CD 10303-42:1992
This is the type of b-spline curve for which the knot values are explicitly given. This subtype shall be used to represent non-uniform B-spline curves and may be used for other knot types.
Let L denote the number of distinct values amongst the d+k+2 knots in the knot list; L will be referred to as the ‘upper index on knots’. Let mj denote the multiplicity (i.e., number of repetitions) of the jth distinct knot. Then:
All knot multiplicities except the first and the last shall be in the range 1,...,d; the first and last may have a maximum value of d + 1. In evaluating the basis functions, a knot u of, e.g., multiplicity 3 is interpreted as a sequence u, u, u,; in the knot array.
NOTE Entity adapted from b_spline_curve_with_knots defined in ISO10303-42.
HISTORY New entity in IFC4.
| # | Attribute | Type | Cardinality | Description | G |
|---|---|---|---|---|---|
| 6 | KnotMultiplicities | IfcInteger | L[2:?] | The multiplicities of the knots. This list defines the number of times each knot in the knots list is to be repeated in constructing the knot array. | X |
| 7 | Knots | IfcParameterValue | L[2:?] | The list of distinct knots used to define the B-spline basis functions. | X |
| 8 | KnotSpec | IfcKnotType | The description of the knot type. This is for information only. | X | |
| UpperIndexOnKnots :=SIZEOF(Knots) | IfcInteger | The upper index on the knot arrays; the lower index is 1. | X |
| Rule | Description |
|---|---|
| ConsistentBSpline | The function IfcConstraintsParamBSpline returns TRUE if no inconsistencies in the parametrisation of the B-spline are found. |
| CorrespondingKnotLists | The number of elements in the knot multiplicities list shall be equal to the number of elements in the knots list. |
| # | 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 | |||||
| IfcCurve | |||||
| Dim :=IfcCurveDim(SELF) | IfcDimensionCount | The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve. | X | ||
| IfcBoundedCurve | |||||
| PositioningElement | IfcLinearPositioningElement @Axis | ? | X | ||
| IfcBSplineCurve | |||||
| 1 | Degree | IfcInteger | The algebraic degree of the basis functions. | X | |
| 2 | ControlPointsList | IfcCartesianPoint | L[2:?] | The list of control points for the curve. | X |
| 3 | CurveForm | IfcBSplineCurveForm | Used to identify particular types of curve; it is for information only. | X | |
| 4 | ClosedCurve | IfcLogical | Indication of whether the curve is closed; it is for information only. | X | |
| 5 | SelfIntersect | IfcLogical | Indication whether the curve self-intersects or not; it is for information only. | X | |
| UpperIndexOnControlPoints :=(SIZEOF(ControlPointsList) - 1) | IfcInteger | The upper index on the array of control points; the lower index is 0. This value is derived from the control points list. | X | ||
| ControlPoints :=IfcListToArray(ControlPointsList,0,UpperIndexOnControlPoints) | IfcCartesianPoint | A[0:UpperIndexOnControlPoints] | The array of control points used to define the geometry of the curve. This is derived from the list of control points. | X | |
| IfcBSplineCurveWithKnots | |||||
| 6 | KnotMultiplicities | IfcInteger | L[2:?] | The multiplicities of the knots. This list defines the number of times each knot in the knots list is to be repeated in constructing the knot array. | X |
| 7 | Knots | IfcParameterValue | L[2:?] | The list of distinct knots used to define the B-spline basis functions. | X |
| 8 | KnotSpec | IfcKnotType | The description of the knot type. This is for information only. | X | |
| UpperIndexOnKnots :=SIZEOF(Knots) | IfcInteger | The upper index on the knot arrays; the lower index is 1. | X | ||
<xs:element name="IfcBSplineCurveWithKnots" type="ifc:IfcBSplineCurveWithKnots" substitutionGroup="ifc:IfcBSplineCurve" nillable="true"/>
<xs:complexType name="IfcBSplineCurveWithKnots">
<xs:complexContent>
<xs:extension base="ifc:IfcBSplineCurve">
<xs:attribute name="KnotMultiplicities" use="optional">
<xs:simpleType>
<xs:restriction>
<xs:simpleType>
<xs:list itemType="ifc:IfcInteger"/>
</xs:simpleType>
<xs:minLength value="2"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name="Knots" use="optional">
<xs:simpleType>
<xs:restriction>
<xs:simpleType>
<xs:list itemType="ifc:IfcParameterValue"/>
</xs:simpleType>
<xs:minLength value="2"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name="KnotSpec" type="ifc:IfcKnotType" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
ENTITY IfcBSplineCurveWithKnots
SUPERTYPE OF(IfcRationalBSplineCurveWithKnots)
SUBTYPE OF (IfcBSplineCurve);
KnotMultiplicities : LIST [2:?] OF IfcInteger;
Knots : LIST [2:?] OF IfcParameterValue;
KnotSpec : IfcKnotType;
DERIVE
UpperIndexOnKnots : IfcInteger := SIZEOF(Knots);
WHERE
ConsistentBSpline : IfcConstraintsParamBSpline(Degree, UpperIndexOnKnots,
UpperIndexOnControlPoints, KnotMultiplicities, Knots);
CorrespondingKnotLists : SIZEOF(KnotMultiplicities) = UpperIndexOnKnots;
END_ENTITY;
EXPRESS-G diagram
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