Definition of the B_spline curve. A B-spline curve can be Uniform or non-uniform Rational or non-rational Periodic or non-periodic. More...

#include <Geom_BSplineCurve.hxx>

Inheritance diagram for Geom_BSplineCurve:

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Public Member Functions
	Geom_BSplineCurve (const NCollection_Array1< gp_Pnt > &Poles, const NCollection_Array1< double > &Knots, const NCollection_Array1< int > &Multiplicities, const int Degree, const bool Periodic=false)
	Creates a non-rational B_spline curve on the basis <Knots, Multiplicities> of degree <Degree>.

	Geom_BSplineCurve (const NCollection_Array1< gp_Pnt > &Poles, const NCollection_Array1< double > &Weights, const NCollection_Array1< double > &Knots, const NCollection_Array1< int > &Multiplicities, const int Degree, const bool Periodic=false, const bool CheckRational=true)
	Creates a rational B_spline curve on the basis <Knots, Multiplicities> of degree <Degree>. Raises ConstructionError subject to the following conditions 0 < Degree <= MaxDegree.

	Geom_BSplineCurve (const Geom_BSplineCurve &theOther)
	Copy constructor for optimized copying without validation.

bool	HasEvalRepresentation () const
	Returns true if an evaluation representation is attached.

const occ::handle< GeomEval_RepCurveDesc::Base > &	EvalRepresentation () const
	Returns the current evaluation representation descriptor (may be null).

void	SetEvalRepresentation (const occ::handle< GeomEval_RepCurveDesc::Base > &theDesc)
	Sets a new evaluation representation. Validates descriptor data and ensures no circular references.

void	ClearEvalRepresentation ()
	Removes the evaluation representation.

void	IncreaseDegree (const int Degree)
	Increases the degree of this BSpline curve to Degree. As a result, the poles, weights and multiplicities tables are modified; the knots table is not changed. Nothing is done if Degree is less than or equal to the current degree. Exceptions Standard_ConstructionError if Degree is greater than Geom_BSplineCurve::MaxDegree().

void	IncreaseMultiplicity (const int Index, const int M)
	Increases the multiplicity of the knot <Index> to <M>.

void	IncreaseMultiplicity (const int I1, const int I2, const int M)
	Increases the multiplicities of the knots in [I1,I2] to <M>.

void	IncrementMultiplicity (const int I1, const int I2, const int M)
	Increment the multiplicities of the knots in [I1,I2] by <M>.

void	InsertKnot (const double U, const int M=1, const double ParametricTolerance=0.0, const bool Add=true)
	Inserts a knot value in the sequence of knots. If is an existing knot the multiplicity is increased by <M>.

void	InsertKnots (const NCollection_Array1< double > &Knots, const NCollection_Array1< int > &Mults, const double ParametricTolerance=0.0, const bool Add=false)
	Inserts a set of knots values in the sequence of knots.

bool	RemoveKnot (const int Index, const int M, const double Tolerance)
	Reduces the multiplicity of the knot of index Index to M. If M is equal to 0, the knot is removed. With a modification of this type, the array of poles is also modified. Two different algorithms are systematically used to compute the new poles of the curve. If, for each pole, the distance between the pole calculated using the first algorithm and the same pole calculated using the second algorithm, is less than Tolerance, this ensures that the curve is not modified by more than Tolerance. Under these conditions, true is returned; otherwise, false is returned. A low tolerance is used to prevent modification of the curve. A high tolerance is used to "smooth" the curve. Exceptions Standard_OutOfRange if Index is outside the bounds of the knots table. pole insertion and pole removing this operation is limited to the Uniform or QuasiUniform BSplineCurve. The knot values are modified. If the BSpline is NonUniform or Piecewise Bezier an exception Construction error is raised.

void	Reverse () final
	Changes the direction of parametrization of <me>. The Knot sequence is modified, the FirstParameter and the LastParameter are not modified. The StartPoint of the initial curve becomes the EndPoint of the reversed curve and the EndPoint of the initial curve becomes the StartPoint of the reversed curve.

double	ReversedParameter (const double U) const final
	Returns the parameter on the reversed curve for the point of parameter U on <me>.

void	Segment (const double U1, const double U2, const double theTolerance=Precision::PConfusion())
	Modifies this BSpline curve by segmenting it between U1 and U2. Either of these values can be outside the bounds of the curve, but U2 must be greater than U1. All data structure tables of this BSpline curve are modified, but the knots located between U1 and U2 are retained. The degree of the curve is not modified.

void	SetKnot (const int Index, const double K)
	Modifies this BSpline curve by assigning the value K to the knot of index Index in the knots table. This is a relatively local modification because K must be such that: Knots(Index - 1) < K < Knots(Index + 1) The second syntax allows you also to increase the multiplicity of the knot to M (but it is not possible to decrease the multiplicity of the knot with this function). Standard_ConstructionError if:

void	SetKnots (const NCollection_Array1< double > &K)
	Modifies this BSpline curve by assigning the array K to its knots table. The multiplicity of the knots is not modified. Exceptions Standard_ConstructionError if the values in the array K are not in ascending order. Standard_OutOfRange if the bounds of the array K are not respectively 1 and the number of knots of this BSpline curve.

void	SetKnot (const int Index, const double K, const int M)
	Changes the knot of range Index with its multiplicity. You can increase the multiplicity of a knot but it is not allowed to decrease the multiplicity of an existing knot.

void	PeriodicNormalization (double &U) const
	returns the parameter normalized within the period if the curve is periodic : otherwise does not do anything

void	SetPeriodic ()
	Changes this BSpline curve into a periodic curve. To become periodic, the curve must first be closed. Next, the knot sequence must be periodic. For this, FirstUKnotIndex and LastUKnotIndex are used to compute I1 and I2, the indexes in the knots array of the knots corresponding to the first and last parameters of this BSpline curve. The period is therefore: Knots(I2) - Knots(I1). Consequently, the knots and poles tables are modified. Exceptions Standard_ConstructionError if this BSpline curve is not closed.

void	SetOrigin (const int Index)
	Assigns the knot of index Index in the knots table as the origin of this periodic BSpline curve. As a consequence, the knots and poles tables are modified. Exceptions Standard_NoSuchObject if this curve is not periodic. Standard_DomainError if Index is outside the bounds of the knots table.

void	SetOrigin (const double U, const double Tol)
	Set the origin of a periodic curve at Knot U. If U is not a knot of the BSpline a new knot is inserted. KnotVector and poles are modified. Raised if the curve is not periodic.

void	SetNotPeriodic ()
	Changes this BSpline curve into a non-periodic curve. If this curve is already non-periodic, it is not modified. Note: the poles and knots tables are modified. Warning If this curve is periodic, as the multiplicity of the first and last knots is not modified, and is not equal to Degree + 1, where Degree is the degree of this BSpline curve, the start and end points of the curve are not its first and last poles.

void	SetPole (const int Index, const gp_Pnt &P)
	Modifies this BSpline curve by assigning P to the pole of index Index in the poles table. Exceptions Standard_OutOfRange if Index is outside the bounds of the poles table. Standard_ConstructionError if Weight is negative or null.

void	SetPole (const int Index, const gp_Pnt &P, const double Weight)
	Modifies this BSpline curve by assigning P to the pole of index Index in the poles table. This syntax also allows you to modify the weight of the modified pole, which becomes Weight. In this case, if this BSpline curve is non-rational, it can become rational and vice versa. Exceptions Standard_OutOfRange if Index is outside the bounds of the poles table. Standard_ConstructionError if Weight is negative or null.

void	SetWeight (const int Index, const double Weight)
	Changes the weight for the pole of range Index. If the curve was non rational it can become rational. If the curve was rational it can become non rational.

void	MovePoint (const double U, const gp_Pnt &P, const int Index1, const int Index2, int &FirstModifiedPole, int &LastModifiedPole)
	Moves the point of parameter U of this BSpline curve to P. Index1 and Index2 are the indexes in the table of poles of this BSpline curve of the first and last poles designated to be moved. FirstModifiedPole and LastModifiedPole are the indexes of the first and last poles which are effectively modified. In the event of incompatibility between Index1, Index2 and the value U:

void	MovePointAndTangent (const double U, const gp_Pnt &P, const gp_Vec &Tangent, const double Tolerance, const int StartingCondition, const int EndingCondition, int &ErrorStatus)
	Move a point with parameter U to P. and makes it tangent at U be Tangent. StartingCondition = -1 means first can move EndingCondition = -1 means last point can move StartingCondition = 0 means the first point cannot move EndingCondition = 0 means the last point cannot move StartingCondition = 1 means the first point and tangent cannot move EndingCondition = 1 means the last point and tangent cannot move and so forth ErrorStatus != 0 means that there are not enough degree of freedom with the constrain to deform the curve accordingly.

bool	IsCN (const int N) const final
	Returns the continuity of the curve, the curve is at least C0. Raised if N < 0.

bool	IsG1 (const double theTf, const double theTl, const double theAngTol) const
	Check if curve has at least G1 continuity in interval [theTf, theTl] Returns true if IsCN(1) or angle between "left" and "right" first derivatives at knots with C0 continuity is less then theAngTol only knots in interval [theTf, theTl] is checked.

bool	IsClosed () const final
	Returns true if the distance between the first point and the last point of the curve is lower or equal to Resolution from package gp. Warnings : The first and the last point can be different from the first pole and the last pole of the curve.

bool	IsPeriodic () const final
	Returns True if the curve is periodic.

bool	IsRational () const
	Returns True if the weights are not identical. The tolerance criterion is Epsilon of the class Real.

GeomAbs_Shape	Continuity () const final
	Returns the global continuity of the curve : C0 : only geometric continuity, C1 : continuity of the first derivative all along the Curve, C2 : continuity of the second derivative all along the Curve, C3 : continuity of the third derivative all along the Curve, CN : the order of continuity is infinite. For a B-spline curve of degree d if a knot Ui has a multiplicity p the B-spline curve is only Cd-p continuous at Ui. So the global continuity of the curve can't be greater than Cd-p where p is the maximum multiplicity of the interior Knots. In the interior of a knot span the curve is infinitely continuously differentiable.

int	Degree () const
	Returns the degree of this BSpline curve. The degree of a Geom_BSplineCurve curve cannot be greater than Geom_BSplineCurve::MaxDegree(). Computation of value and derivatives.

gp_Pnt	EvalD0 (const double U) const final
	Returns the point of parameter U.

Geom_Curve::ResD1	EvalD1 (const double U) const final
	Raised if the continuity of the curve is not C1.

Geom_Curve::ResD2	EvalD2 (const double U) const final
	Raised if the continuity of the curve is not C2.

Geom_Curve::ResD3	EvalD3 (const double U) const final
	Raised if the continuity of the curve is not C3.

gp_Vec	EvalDN (const double U, const int N) const final
	For the point of parameter U of this BSpline curve, computes the vector corresponding to the Nth derivative. Warning On a point where the continuity of the curve is not the one requested, this function impacts the part defined by the parameter with a value greater than U, i.e. the part of the curve to the "right" of the singularity. Exceptions Standard_RangeError if N is less than 1.

gp_Pnt	LocalValue (const double U, const int FromK1, const int ToK2) const
	Raised if FromK1 = ToK2.

void	LocalD0 (const double U, const int FromK1, const int ToK2, gp_Pnt &P) const
	Raised if FromK1 = ToK2.

void	LocalD1 (const double U, const int FromK1, const int ToK2, gp_Pnt &P, gp_Vec &V1) const
	Raised if the local continuity of the curve is not C1 between the knot K1 and the knot K2. Raised if FromK1 = ToK2.

void	LocalD2 (const double U, const int FromK1, const int ToK2, gp_Pnt &P, gp_Vec &V1, gp_Vec &V2) const
	Raised if the local continuity of the curve is not C2 between the knot K1 and the knot K2. Raised if FromK1 = ToK2.

void	LocalD3 (const double U, const int FromK1, const int ToK2, gp_Pnt &P, gp_Vec &V1, gp_Vec &V2, gp_Vec &V3) const
	Raised if the local continuity of the curve is not C3 between the knot K1 and the knot K2. Raised if FromK1 = ToK2.

gp_Vec	LocalDN (const double U, const int FromK1, const int ToK2, const int N) const
	Raised if the local continuity of the curve is not CN between the knot K1 and the knot K2. Raised if FromK1 = ToK2. Raised if N < 1.

gp_Pnt	EndPoint () const final
	Returns the last point of the curve. Warnings : The last point of the curve is different from the last pole of the curve if the multiplicity of the last knot is lower than Degree.

int	FirstUKnotIndex () const
	Returns the index in the knot array of the knot corresponding to the first or last parameter of this BSpline curve. For a BSpline curve, the first (or last) parameter (which gives the start (or end) point of the curve) is a knot value. However, if the multiplicity of the first (or last) knot is less than Degree + 1, where Degree is the degree of the curve, it is not the first (or last) knot of the curve.

double	FirstParameter () const final
	Returns the value of the first parameter of this BSpline curve. This is a knot value. The first parameter is the one of the start point of the BSpline curve.

double	Knot (const int Index) const
	Returns the knot of range Index. When there is a knot with a multiplicity greater than 1 the knot is not repeated. The method Multiplicity can be used to get the multiplicity of the Knot. Raised if Index < 1 or Index > NbKnots.

void	Knots (NCollection_Array1< double > &K) const
	returns the knot values of the B-spline curve; Warning A knot with a multiplicity greater than 1 is not repeated in the knot table. The Multiplicity function can be used to obtain the multiplicity of each knot.

const NCollection_Array1< double > &	Knots () const
	returns the knot values of the B-spline curve; Warning A knot with a multiplicity greater than 1 is not repeated in the knot table. The Multiplicity function can be used to obtain the multiplicity of each knot.

void	KnotSequence (NCollection_Array1< double > &K) const
	Returns K, the knots sequence of this BSpline curve. In this sequence, knots with a multiplicity greater than 1 are repeated. In the case of a non-periodic curve the length of the sequence must be equal to the sum of the NbKnots multiplicities of the knots of the curve (where NbKnots is the number of knots of this BSpline curve). This sum is also equal to : NbPoles + Degree + 1 where NbPoles is the number of poles and Degree the degree of this BSpline curve. In the case of a periodic curve, if there are k periodic knots, the period is Knot(k+1) - Knot(1). The initial sequence is built by writing knots 1 to k+1, which are repeated according to their corresponding multiplicities. If Degree is the degree of the curve, the degree of continuity of the curve at the knot of index 1 (or k+1) is equal to c = Degree + 1 - Mult(1). c knots are then inserted at the beginning and end of the initial sequence:

const NCollection_Array1< double > &	KnotSequence () const
	returns the knots of the B-spline curve. Knots with multiplicit greater than 1 are repeated

GeomAbs_BSplKnotDistribution	KnotDistribution () const
	Returns NonUniform or Uniform or QuasiUniform or PiecewiseBezier. If all the knots differ by a positive constant from the preceding knot the BSpline Curve can be :

int	LastUKnotIndex () const
	For a BSpline curve the last parameter (which gives the end point of the curve) is a knot value but if the multiplicity of the last knot index is lower than Degree + 1 it is not the last knot of the curve. This method computes the index of the knot corresponding to the last parameter.

double	LastParameter () const final
	Computes the parametric value of the end point of the curve. It is a knot value.

void	LocateU (const double U, const double ParametricTolerance, int &I1, int &I2, const bool WithKnotRepetition=false) const
	Locates the parametric value U in the sequence of knots. If "WithKnotRepetition" is True we consider the knot's representation with repetition of multiple knot value, otherwise we consider the knot's representation with no repetition of multiple knot values. Knots (I1) <= U <= Knots (I2) . if I1 = I2 U is a knot value (the tolerance criterion ParametricTolerance is used). . if I1 < 1 => U < Knots (1) - std::abs(ParametricTolerance) . if I2 > NbKnots => U > Knots (NbKnots) + std::abs(ParametricTolerance)

int	Multiplicity (const int Index) const
	Returns the multiplicity of the knots of range Index. Raised if Index < 1 or Index > NbKnots.

void	Multiplicities (NCollection_Array1< int > &M) const
	Returns the multiplicity of the knots of the curve.

const NCollection_Array1< int > &	Multiplicities () const
	returns the multiplicity of the knots of the curve.

int	NbKnots () const
	Returns the number of knots. This method returns the number of knot without repetition of multiple knots.

int	NbPoles () const
	Returns the number of poles.

const gp_Pnt &	Pole (const int Index) const
	Returns the pole of range Index. Raised if Index < 1 or Index > NbPoles.

void	Poles (NCollection_Array1< gp_Pnt > &P) const
	Returns the poles of the B-spline curve;.

const NCollection_Array1< gp_Pnt > &	Poles () const
	Returns the poles of the B-spline curve;.

gp_Pnt	StartPoint () const final
	Returns the start point of the curve. Warnings : This point is different from the first pole of the curve if the multiplicity of the first knot is lower than Degree.

double	Weight (const int Index) const
	Returns the weight of the pole of range Index . Raised if Index < 1 or Index > NbPoles.

void	Weights (NCollection_Array1< double > &W) const
	Returns the weights of the B-spline curve;.

const NCollection_Array1< double > *	Weights () const
	Returns the weights of the B-spline curve;.

const NCollection_Array1< double > &	WeightsArray () const
	Returns a const reference to the weights array. For rational curves: the internal owning weights array. For non-rational curves: a non-owning view of unit weights from BSplCLib. The array is always sized to match NbPoles().

void	Transform (const gp_Trsf &T) final
	Applies the transformation T to this BSpline curve.

void	Resolution (const double Tolerance3D, double &UTolerance)
	Computes for this BSpline curve the parametric tolerance UTolerance for a given 3D tolerance Tolerance3D. If f(t) is the equation of this BSpline curve, UTolerance ensures that: \| t1 - t0\| < Utolerance ===> \|f(t1) - f(t0)\| < Tolerance3D.

occ::handle< Geom_Geometry >	Copy () const final
	Creates a new object which is a copy of this BSpline curve.

bool	IsEqual (const occ::handle< Geom_BSplineCurve > &theOther, const double thePreci) const
	Compare two Bspline curve on identity;.

void	DumpJson (Standard_OStream &theOStream, int theDepth=-1) const final
	Dumps the content of me into the stream.

Public Member Functions inherited from Geom_Curve
virtual double	TransformedParameter (const double U, const gp_Trsf &T) const
	Returns the parameter on the transformed curve for the transform of the point of parameter U on <me>.

virtual double	ParametricTransformation (const gp_Trsf &T) const
	Returns a coefficient to compute the parameter on the transformed curve for the transform of the point on <me>.

occ::handle< Geom_Curve >	Reversed () const
	Returns a copy of <me> reversed.

virtual double	Period () const
	Returns the period of this curve. Exceptions Standard_NoSuchObject if this curve is not periodic.

void	D0 (const double U, gp_Pnt &P) const
	Returns in P the point of parameter U.

void	D1 (const double U, gp_Pnt &P, gp_Vec &V1) const
	Returns the point P of parameter U and the first derivative V1.

void	D2 (const double U, gp_Pnt &P, gp_Vec &V1, gp_Vec &V2) const
	Returns the point P of parameter U, the first and second derivatives V1 and V2.

void	D3 (const double U, gp_Pnt &P, gp_Vec &V1, gp_Vec &V2, gp_Vec &V3) const
	Returns the point P of parameter U, the first, the second and the third derivative.

gp_Vec	DN (const double U, const int N) const
	The returned vector gives the value of the derivative for the order of derivation N.

gp_Pnt	Value (const double U) const
	Computes the point of parameter U on <me>.

void	DumpJson (Standard_OStream &theOStream, int theDepth=-1) const override
	Dumps the content of me into the stream.

Public Member Functions inherited from Geom_Geometry
void	Mirror (const gp_Pnt &P)
	Performs the symmetrical transformation of a Geometry with respect to the point P which is the center of the symmetry.

void	Mirror (const gp_Ax1 &A1)
	Performs the symmetrical transformation of a Geometry with respect to an axis placement which is the axis of the symmetry.

void	Mirror (const gp_Ax2 &A2)
	Performs the symmetrical transformation of a Geometry with respect to a plane. The axis placement A2 locates the plane of the symmetry : (Location, XDirection, YDirection).

void	Rotate (const gp_Ax1 &A1, const double Ang)
	Rotates a Geometry. A1 is the axis of the rotation. Ang is the angular value of the rotation in radians.

void	Scale (const gp_Pnt &P, const double S)
	Scales a Geometry. S is the scaling value.

void	Translate (const gp_Vec &V)
	Translates a Geometry. V is the vector of the translation.

void	Translate (const gp_Pnt &P1, const gp_Pnt &P2)
	Translates a Geometry from the point P1 to the point P2.

occ::handle< Geom_Geometry >	Mirrored (const gp_Pnt &P) const

occ::handle< Geom_Geometry >	Mirrored (const gp_Ax1 &A1) const

occ::handle< Geom_Geometry >	Mirrored (const gp_Ax2 &A2) const

occ::handle< Geom_Geometry >	Rotated (const gp_Ax1 &A1, const double Ang) const

occ::handle< Geom_Geometry >	Scaled (const gp_Pnt &P, const double S) const

occ::handle< Geom_Geometry >	Transformed (const gp_Trsf &T) const

occ::handle< Geom_Geometry >	Translated (const gp_Vec &V) const

occ::handle< Geom_Geometry >	Translated (const gp_Pnt &P1, const gp_Pnt &P2) const

Public Member Functions inherited from Standard_Transient
	Standard_Transient ()
	Empty constructor.

	Standard_Transient (const Standard_Transient &)
	Copy constructor – does nothing.

Standard_Transient &	operator= (const Standard_Transient &)
	Assignment operator, needed to avoid copying reference counter.

virtual	~Standard_Transient ()=default
	Destructor must be virtual.

virtual const opencascade::handle< Standard_Type > &	DynamicType () const
	Returns a type descriptor about this object.

bool	IsInstance (const opencascade::handle< Standard_Type > &theType) const
	Returns a true value if this is an instance of Type.

bool	IsInstance (const char *const theTypeName) const
	Returns a true value if this is an instance of TypeName.

bool	IsKind (const opencascade::handle< Standard_Type > &theType) const
	Returns true if this is an instance of Type or an instance of any class that inherits from Type. Note that multiple inheritance is not supported by OCCT RTTI mechanism.

bool	IsKind (const char *const theTypeName) const
	Returns true if this is an instance of TypeName or an instance of any class that inherits from TypeName. Note that multiple inheritance is not supported by OCCT RTTI mechanism.

Standard_Transient *	This () const
	Returns non-const pointer to this object (like const_cast). For protection against creating handle to objects allocated in stack or call from constructor, it will raise exception Standard_ProgramError if reference counter is zero.

int	GetRefCount () const noexcept
	Get the reference counter of this object.

void	IncrementRefCounter () noexcept
	Increments the reference counter of this object. Uses relaxed memory ordering since incrementing only requires atomicity, not synchronization with other memory operations.

int	DecrementRefCounter () noexcept
	Decrements the reference counter of this object; returns the decremented value. Uses release ordering for the decrement to ensure all writes to the object are visible before the count reaches zero. An acquire fence is added only when the count reaches zero, ensuring proper synchronization before deletion. This is more efficient than using acq_rel for every decrement.

virtual void	Delete () const
	Memory deallocator for transient classes.

Static Public Member Functions
static int	MaxDegree ()
	Returns the value of the maximum degree of the normalized B-spline basis functions in this package.

Static Public Member Functions inherited from Standard_Transient
static constexpr const char *	get_type_name ()
	Returns a type descriptor about this object.

static const opencascade::handle< Standard_Type > &	get_type_descriptor ()
	Returns type descriptor of Standard_Transient class.

Protected Member Functions
void	updateKnots ()
	Recompute the flatknots, the knotsdistribution, the continuity.

Additional Inherited Members
Public Types inherited from Standard_Transient
typedef void	base_type
	Returns a type descriptor about this object.

Detailed Description

Definition of the B_spline curve. A B-spline curve can be Uniform or non-uniform Rational or non-rational Periodic or non-periodic.

a b-spline curve is defined by : its degree; the degree for a Geom_BSplineCurve is limited to a value (25) which is defined and controlled by the system. This value is returned by the function MaxDegree;

its periodic or non-periodic nature;
a table of poles (also called control points), with their associated weights if the BSpline curve is rational. The poles of the curve are "control points" used to deform the curve. If the curve is non-periodic, the first pole is the start point of the curve, and the last pole is the end point of the curve. The segment which joins the first pole to the second pole is the tangent to the curve at its start point, and the segment which joins the last pole to the second-from-last pole is the tangent to the curve at its end point. If the curve is periodic, these geometric properties are not verified. It is more difficult to give a geometric signification to the weights but are useful for providing exact representations of the arcs of a circle or ellipse. Moreover, if the weights of all the poles are equal, the curve has a polynomial equation; it is therefore a non-rational curve.
a table of knots with their multiplicities. For a Geom_BSplineCurve, the table of knots is an increasing sequence of reals without repetition; the multiplicities define the repetition of the knots. A BSpline curve is a piecewise polynomial or rational curve. The knots are the parameters of junction points between two pieces. The multiplicity Mult(i) of the knot Knot(i) of the BSpline curve is related to the degree of continuity of the curve at the knot Knot(i), which is equal to Degree - Mult(i) where Degree is the degree of the BSpline curve. If the knots are regularly spaced (i.e. the difference between two consecutive knots is a constant), three specific and frequently used cases of knot distribution can be identified:
"uniform" if all multiplicities are equal to 1,
"quasi-uniform" if all multiplicities are equal to 1, except the first and the last knot which have a multiplicity of Degree + 1, where Degree is the degree of the BSpline curve,
"Piecewise Bezier" if all multiplicities are equal to Degree except the first and last knot which have a multiplicity of Degree + 1, where Degree is the degree of the BSpline curve. A curve of this type is a concatenation of arcs of Bezier curves. If the BSpline curve is not periodic:
the bounds of the Poles and Weights tables are 1 and NbPoles, where NbPoles is the number of poles of the BSpline curve,
the bounds of the Knots and Multiplicities tables are 1 and NbKnots, where NbKnots is the number of knots of the BSpline curve. If the BSpline curve is periodic, and if there are k periodic knots and p periodic poles, the period is: period = Knot(k + 1) - Knot(1) and the poles and knots tables can be considered as infinite tables, verifying:
Knot(i+k) = Knot(i) + period
Pole(i+p) = Pole(i) Note: data structures of a periodic BSpline curve are more complex than those of a non-periodic one. Warning In this class, weight value is considered to be zero if the weight is less than or equal to gp::Resolution().

References : . A survey of curve and surface methods in CADG Wolfgang BOHM CAGD 1 (1984) . On de Boor-like algorithms and blossoming Wolfgang BOEHM cagd 5 (1988) . Blossoming and knot insertion algorithms for B-spline curves Ronald N. GOLDMAN . Modelisation des surfaces en CAO, Henri GIAUME Peugeot SA . Curves and Surfaces for Computer Aided Geometric Design, a practical guide Gerald Farin

Constructor & Destructor Documentation

◆ Geom_BSplineCurve() [1/3]

Geom_BSplineCurve::Geom_BSplineCurve	(	const NCollection_Array1< gp_Pnt > &	Poles,
		const NCollection_Array1< double > &	Knots,
		const NCollection_Array1< int > &	Multiplicities,
		const int	Degree,
		const bool	Periodic = false )

Creates a non-rational B_spline curve on the basis <Knots, Multiplicities> of degree <Degree>.

◆ Geom_BSplineCurve() [2/3]

Geom_BSplineCurve::Geom_BSplineCurve	(	const NCollection_Array1< gp_Pnt > &	Poles,
		const NCollection_Array1< double > &	Weights,
		const NCollection_Array1< double > &	Knots,
		const NCollection_Array1< int > &	Multiplicities,
		const int	Degree,
		const bool	Periodic = false,
		const bool	CheckRational = true )

Creates a rational B_spline curve on the basis <Knots, Multiplicities> of degree <Degree>. Raises ConstructionError subject to the following conditions 0 < Degree <= MaxDegree.

Weights.Length() == Poles.Length()

Knots.Length() == Mults.Length() >= 2

Knots(i) < Knots(i+1) (Knots are increasing)

1 <= Mults(i) <= Degree

On a non periodic curve the first and last multiplicities may be Degree+1 (this is even recommended if you want the curve to start and finish on the first and last pole).

On a periodic curve the first and the last multicities must be the same.

on non-periodic curves

Poles.Length() == Sum(Mults(i)) - Degree - 1 >= 2

on periodic curves

Poles.Length() == Sum(Mults(i)) except the first or last

◆ Geom_BSplineCurve() [3/3]

Geom_BSplineCurve::Geom_BSplineCurve ( const Geom_BSplineCurve & theOther )

Copy constructor for optimized copying without validation.

Parameters

[in] theOther the BSpline curve to copy from

Member Function Documentation

◆ ClearEvalRepresentation()

void Geom_BSplineCurve::ClearEvalRepresentation ( )

inline

Removes the evaluation representation.

◆ Continuity()

GeomAbs_Shape Geom_BSplineCurve::Continuity ( ) const

finalvirtual

Returns the global continuity of the curve : C0 : only geometric continuity, C1 : continuity of the first derivative all along the Curve, C2 : continuity of the second derivative all along the Curve, C3 : continuity of the third derivative all along the Curve, CN : the order of continuity is infinite. For a B-spline curve of degree d if a knot Ui has a multiplicity p the B-spline curve is only Cd-p continuous at Ui. So the global continuity of the curve can't be greater than Cd-p where p is the maximum multiplicity of the interior Knots. In the interior of a knot span the curve is infinitely continuously differentiable.

Implements Geom_Curve.

◆ Copy()

occ::handle< Geom_Geometry > Geom_BSplineCurve::Copy ( ) const

finalvirtual

Creates a new object which is a copy of this BSpline curve.

Implements Geom_Geometry.

◆ Degree()

int Geom_BSplineCurve::Degree ( ) const

Returns the degree of this BSpline curve. The degree of a Geom_BSplineCurve curve cannot be greater than Geom_BSplineCurve::MaxDegree(). Computation of value and derivatives.

◆ DumpJson()

void Geom_BSplineCurve::DumpJson	(	Standard_OStream &	theOStream,
		int	theDepth = -1 ) const

finalvirtual

Dumps the content of me into the stream.

Reimplemented from Geom_BoundedCurve.

◆ EndPoint()

gp_Pnt Geom_BSplineCurve::EndPoint ( ) const

finalvirtual

Returns the last point of the curve. Warnings : The last point of the curve is different from the last pole of the curve if the multiplicity of the last knot is lower than Degree.

Implements Geom_BoundedCurve.

◆ EvalD0()

gp_Pnt Geom_BSplineCurve::EvalD0 ( const double U ) const

finalvirtual

Returns the point of parameter U.

Implements Geom_Curve.

◆ EvalD1()

Geom_Curve::ResD1 Geom_BSplineCurve::EvalD1 ( const double U ) const

finalvirtual

Raised if the continuity of the curve is not C1.

Implements Geom_Curve.

◆ EvalD2()

Geom_Curve::ResD2 Geom_BSplineCurve::EvalD2 ( const double U ) const

finalvirtual

Raised if the continuity of the curve is not C2.

Implements Geom_Curve.

◆ EvalD3()

Geom_Curve::ResD3 Geom_BSplineCurve::EvalD3 ( const double U ) const

finalvirtual

Raised if the continuity of the curve is not C3.

Implements Geom_Curve.

◆ EvalDN()

gp_Vec Geom_BSplineCurve::EvalDN	(	const double	U,
		const int	N ) const

finalvirtual

For the point of parameter U of this BSpline curve, computes the vector corresponding to the Nth derivative. Warning On a point where the continuity of the curve is not the one requested, this function impacts the part defined by the parameter with a value greater than U, i.e. the part of the curve to the "right" of the singularity. Exceptions Standard_RangeError if N is less than 1.

The following functions compute the point of parameter U and the derivatives at this point on the B-spline curve arc defined between the knot FromK1 and the knot ToK2. U can be out of bounds [Knot (FromK1), Knot (ToK2)] but for the computation we only use the definition of the curve between these two knots. This method is useful to compute local derivative, if the order of continuity of the whole curve is not greater enough. Inside the parametric domain Knot (FromK1), Knot (ToK2) the evaluations are the same as if we consider the whole definition of the curve. Of course the evaluations are different outside this parametric domain.

Implements Geom_Curve.

◆ EvalRepresentation()

const occ::handle< GeomEval_RepCurveDesc::Base > & Geom_BSplineCurve::EvalRepresentation ( ) const

inline

Returns the current evaluation representation descriptor (may be null).

◆ FirstParameter()

double Geom_BSplineCurve::FirstParameter ( ) const

finalvirtual

Returns the value of the first parameter of this BSpline curve. This is a knot value. The first parameter is the one of the start point of the BSpline curve.

Implements Geom_Curve.

◆ FirstUKnotIndex()

int Geom_BSplineCurve::FirstUKnotIndex ( ) const

Returns the index in the knot array of the knot corresponding to the first or last parameter of this BSpline curve. For a BSpline curve, the first (or last) parameter (which gives the start (or end) point of the curve) is a knot value. However, if the multiplicity of the first (or last) knot is less than Degree + 1, where Degree is the degree of the curve, it is not the first (or last) knot of the curve.

◆ HasEvalRepresentation()

bool Geom_BSplineCurve::HasEvalRepresentation ( ) const

inline

Returns true if an evaluation representation is attached.

◆ IncreaseDegree()

void Geom_BSplineCurve::IncreaseDegree ( const int Degree )

Increases the degree of this BSpline curve to Degree. As a result, the poles, weights and multiplicities tables are modified; the knots table is not changed. Nothing is done if Degree is less than or equal to the current degree. Exceptions Standard_ConstructionError if Degree is greater than Geom_BSplineCurve::MaxDegree().

◆ IncreaseMultiplicity() [1/2]

void Geom_BSplineCurve::IncreaseMultiplicity	(	const int	I1,
		const int	I2,
		const int	M )

Increases the multiplicities of the knots in [I1,I2] to <M>.

For each knot if <M> is lower or equal to the current multiplicity nothing is done. If <M> is higher than the degree the degree is used. If <I1,I2> are not in [FirstUKnotIndex, LastUKnotIndex]

◆ IncreaseMultiplicity() [2/2]

void Geom_BSplineCurve::IncreaseMultiplicity	(	const int	Index,
		const int	M )

Increases the multiplicity of the knot <Index> to <M>.

If <M> is lower or equal to the current multiplicity nothing is done. If <M> is higher than the degree, the degree is used. If <Index> is not in [FirstUKnotIndex, LastUKnotIndex]

◆ IncrementMultiplicity()

void Geom_BSplineCurve::IncrementMultiplicity	(	const int	I1,
		const int	I2,
		const int	M )

Increment the multiplicities of the knots in [I1,I2] by <M>.

If <M> is not positive nothing is done.

For each knot the resulting multiplicity is limited to the Degree. If <I1,I2> are not in [FirstUKnotIndex, LastUKnotIndex]

◆ InsertKnot()

void Geom_BSplineCurve::InsertKnot	(	const double	U,
		const int	M = 1,
		const double	ParametricTolerance = 0.0,
		const bool	Add = true )

Inserts a knot value in the sequence of knots. If is an existing knot the multiplicity is increased by <M>.

If U is not on the parameter range nothing is done.

If the multiplicity is negative or null nothing is done. The new multiplicity is limited to the degree.

The tolerance criterion for knots equality is the max of Epsilon(U) and ParametricTolerance.

◆ InsertKnots()

void Geom_BSplineCurve::InsertKnots	(	const NCollection_Array1< double > &	Knots,
		const NCollection_Array1< int > &	Mults,
		const double	ParametricTolerance = 0.0,
		const bool	Add = false )

Inserts a set of knots values in the sequence of knots.

For each U = Knots(i), M = Mults(i)

If is an existing knot the multiplicity is increased by <M> if <Add> is True, increased to <M> if <Add> is False.

If U is not on the parameter range nothing is done.

If the multiplicity is negative or null nothing is done. The new multiplicity is limited to the degree.

The tolerance criterion for knots equality is the max of Epsilon(U) and ParametricTolerance.

◆ IsClosed()

bool Geom_BSplineCurve::IsClosed ( ) const

finalvirtual

Returns true if the distance between the first point and the last point of the curve is lower or equal to Resolution from package gp. Warnings : The first and the last point can be different from the first pole and the last pole of the curve.

Implements Geom_Curve.

◆ IsCN()

bool Geom_BSplineCurve::IsCN ( const int N ) const

finalvirtual

Returns the continuity of the curve, the curve is at least C0. Raised if N < 0.

Implements Geom_Curve.

◆ IsEqual()

bool Geom_BSplineCurve::IsEqual	(	const occ::handle< Geom_BSplineCurve > &	theOther,
		const double	thePreci ) const

Compare two Bspline curve on identity;.

◆ IsG1()

bool Geom_BSplineCurve::IsG1	(	const double	theTf,
		const double	theTl,
		const double	theAngTol ) const

Check if curve has at least G1 continuity in interval [theTf, theTl] Returns true if IsCN(1) or angle between "left" and "right" first derivatives at knots with C0 continuity is less then theAngTol only knots in interval [theTf, theTl] is checked.

◆ IsPeriodic()

bool Geom_BSplineCurve::IsPeriodic ( ) const

finalvirtual

Returns True if the curve is periodic.

Implements Geom_Curve.

◆ IsRational()

bool Geom_BSplineCurve::IsRational ( ) const

Returns True if the weights are not identical. The tolerance criterion is Epsilon of the class Real.

◆ Knot()

double Geom_BSplineCurve::Knot ( const int Index ) const

Returns the knot of range Index. When there is a knot with a multiplicity greater than 1 the knot is not repeated. The method Multiplicity can be used to get the multiplicity of the Knot. Raised if Index < 1 or Index > NbKnots.

◆ KnotDistribution()

GeomAbs_BSplKnotDistribution Geom_BSplineCurve::KnotDistribution ( ) const

Returns NonUniform or Uniform or QuasiUniform or PiecewiseBezier. If all the knots differ by a positive constant from the preceding knot the BSpline Curve can be :

Uniform if all the knots are of multiplicity 1,
QuasiUniform if all the knots are of multiplicity 1 except for the first and last knot which are of multiplicity Degree + 1,
PiecewiseBezier if the first and last knots have multiplicity Degree + 1 and if interior knots have multiplicity Degree A piecewise Bezier with only two knots is a BezierCurve. else the curve is non uniform. The tolerance criterion is Epsilon from class Real.

◆ Knots() [1/2]

const NCollection_Array1< double > & Geom_BSplineCurve::Knots ( ) const

returns the knot values of the B-spline curve; Warning A knot with a multiplicity greater than 1 is not repeated in the knot table. The Multiplicity function can be used to obtain the multiplicity of each knot.

◆ Knots() [2/2]

void Geom_BSplineCurve::Knots ( NCollection_Array1< double > & K ) const

returns the knot values of the B-spline curve; Warning A knot with a multiplicity greater than 1 is not repeated in the knot table. The Multiplicity function can be used to obtain the multiplicity of each knot.

Raised K.Lower() is less than number of first knot or K.Upper() is more than number of last knot.

Deprecated: ("use Knots() returning const reference instead")

◆ KnotSequence() [1/2]

const NCollection_Array1< double > & Geom_BSplineCurve::KnotSequence ( ) const

returns the knots of the B-spline curve. Knots with multiplicit greater than 1 are repeated

◆ KnotSequence() [2/2]

void Geom_BSplineCurve::KnotSequence ( NCollection_Array1< double > & K ) const

Returns K, the knots sequence of this BSpline curve. In this sequence, knots with a multiplicity greater than 1 are repeated. In the case of a non-periodic curve the length of the sequence must be equal to the sum of the NbKnots multiplicities of the knots of the curve (where NbKnots is the number of knots of this BSpline curve). This sum is also equal to : NbPoles + Degree + 1 where NbPoles is the number of poles and Degree the degree of this BSpline curve. In the case of a periodic curve, if there are k periodic knots, the period is Knot(k+1) - Knot(1). The initial sequence is built by writing knots 1 to k+1, which are repeated according to their corresponding multiplicities. If Degree is the degree of the curve, the degree of continuity of the curve at the knot of index 1 (or k+1) is equal to c = Degree + 1 - Mult(1). c knots are then inserted at the beginning and end of the initial sequence:

the c values of knots preceding the first item Knot(k+1) in the initial sequence are inserted at the beginning; the period is subtracted from these c values;
the c values of knots following the last item Knot(1) in the initial sequence are inserted at the end; the period is added to these c values. The length of the sequence must therefore be equal to: NbPoles + 2*Degree - Mult(1) + 2. Example For a non-periodic BSpline curve of degree 2 where:
the array of knots is: { k1 k2 k3 k4 },
with associated multiplicities: { 3 1 2 3 }, the knot sequence is: K = { k1 k1 k1 k2 k3 k3 k4 k4 k4 } For a periodic BSpline curve of degree 4 , which is "C1" continuous at the first knot, and where :
the periodic knots are: { k1 k2 k3 (k4) } (3 periodic knots: the points of parameter k1 and k4 are identical, the period is p = k4 - k1),
with associated multiplicities: { 3 1 2 (3) }, the degree of continuity at knots k1 and k4 is: Degree + 1 - Mult(i) = 2. 2 supplementary knots are added at the beginning and end of the sequence:
at the beginning: the 2 knots preceding k4 minus the period; in this example, this is k3 - p both times;
at the end: the 2 knots following k1 plus the period; in this example, this is k2 + p and k3 + p. The knot sequence is therefore: K = { k3-p k3-p k1 k1 k1 k2 k3 k3 k4 k4 k4 k2+p k3+p } Exceptions Raised if K.Lower() is less than number of first knot in knot sequence with repetitions or K.Upper() is more than number of last knot in knot sequence with repetitions.
Deprecated
("use KnotSequence() returning const reference instead")

◆ LastParameter()

double Geom_BSplineCurve::LastParameter ( ) const

finalvirtual

Computes the parametric value of the end point of the curve. It is a knot value.

Implements Geom_Curve.

◆ LastUKnotIndex()

int Geom_BSplineCurve::LastUKnotIndex ( ) const

For a BSpline curve the last parameter (which gives the end point of the curve) is a knot value but if the multiplicity of the last knot index is lower than Degree + 1 it is not the last knot of the curve. This method computes the index of the knot corresponding to the last parameter.

◆ LocalD0()

void Geom_BSplineCurve::LocalD0	(	const double	U,
		const int	FromK1,
		const int	ToK2,
		gp_Pnt &	P ) const

Raised if FromK1 = ToK2.

◆ LocalD1()

void Geom_BSplineCurve::LocalD1	(	const double	U,
		const int	FromK1,
		const int	ToK2,
		gp_Pnt &	P,
		gp_Vec &	V1 ) const

Raised if the local continuity of the curve is not C1 between the knot K1 and the knot K2. Raised if FromK1 = ToK2.

◆ LocalD2()

void Geom_BSplineCurve::LocalD2	(	const double	U,
		const int	FromK1,
		const int	ToK2,
		gp_Pnt &	P,
		gp_Vec &	V1,
		gp_Vec &	V2 ) const

Raised if the local continuity of the curve is not C2 between the knot K1 and the knot K2. Raised if FromK1 = ToK2.

◆ LocalD3()

void Geom_BSplineCurve::LocalD3	(	const double	U,
		const int	FromK1,
		const int	ToK2,
		gp_Pnt &	P,
		gp_Vec &	V1,
		gp_Vec &	V2,
		gp_Vec &	V3 ) const

Raised if the local continuity of the curve is not C3 between the knot K1 and the knot K2. Raised if FromK1 = ToK2.

◆ LocalDN()

gp_Vec Geom_BSplineCurve::LocalDN	(	const double	U,
		const int	FromK1,
		const int	ToK2,
		const int	N ) const

Raised if the local continuity of the curve is not CN between the knot K1 and the knot K2. Raised if FromK1 = ToK2. Raised if N < 1.

◆ LocalValue()

gp_Pnt Geom_BSplineCurve::LocalValue	(	const double	U,
		const int	FromK1,
		const int	ToK2 ) const

Raised if FromK1 = ToK2.

◆ LocateU()

void Geom_BSplineCurve::LocateU	(	const double	U,
		const double	ParametricTolerance,
		int &	I1,
		int &	I2,
		const bool	WithKnotRepetition = false ) const

Locates the parametric value U in the sequence of knots. If "WithKnotRepetition" is True we consider the knot's representation with repetition of multiple knot value, otherwise we consider the knot's representation with no repetition of multiple knot values. Knots (I1) <= U <= Knots (I2) . if I1 = I2 U is a knot value (the tolerance criterion ParametricTolerance is used). . if I1 < 1 => U < Knots (1) - std::abs(ParametricTolerance) . if I2 > NbKnots => U > Knots (NbKnots) + std::abs(ParametricTolerance)

◆ MaxDegree()

static int Geom_BSplineCurve::MaxDegree ( )

static

Returns the value of the maximum degree of the normalized B-spline basis functions in this package.

◆ MovePoint()

void Geom_BSplineCurve::MovePoint	(	const double	U,
		const gp_Pnt &	P,
		const int	Index1,
		const int	Index2,
		int &	FirstModifiedPole,
		int &	LastModifiedPole )

Moves the point of parameter U of this BSpline curve to P. Index1 and Index2 are the indexes in the table of poles of this BSpline curve of the first and last poles designated to be moved. FirstModifiedPole and LastModifiedPole are the indexes of the first and last poles which are effectively modified. In the event of incompatibility between Index1, Index2 and the value U:

no change is made to this BSpline curve, and
the FirstModifiedPole and LastModifiedPole are returned null. Exceptions Standard_OutOfRange if:
Index1 is greater than or equal to Index2, or
Index1 or Index2 is less than 1 or greater than the number of poles of this BSpline curve.

◆ MovePointAndTangent()

void Geom_BSplineCurve::MovePointAndTangent	(	const double	U,
		const gp_Pnt &	P,
		const gp_Vec &	Tangent,
		const double	Tolerance,
		const int	StartingCondition,
		const int	EndingCondition,
		int &	ErrorStatus )

Move a point with parameter U to P. and makes it tangent at U be Tangent. StartingCondition = -1 means first can move EndingCondition = -1 means last point can move StartingCondition = 0 means the first point cannot move EndingCondition = 0 means the last point cannot move StartingCondition = 1 means the first point and tangent cannot move EndingCondition = 1 means the last point and tangent cannot move and so forth ErrorStatus != 0 means that there are not enough degree of freedom with the constrain to deform the curve accordingly.

◆ Multiplicities() [1/2]

const NCollection_Array1< int > & Geom_BSplineCurve::Multiplicities ( ) const

returns the multiplicity of the knots of the curve.

◆ Multiplicities() [2/2]

void Geom_BSplineCurve::Multiplicities ( NCollection_Array1< int > & M ) const

Returns the multiplicity of the knots of the curve.

Raised if the length of M is not equal to NbKnots.

Deprecated: ("use Multiplicities() returning const reference instead")

◆ Multiplicity()

int Geom_BSplineCurve::Multiplicity ( const int Index ) const

Returns the multiplicity of the knots of range Index. Raised if Index < 1 or Index > NbKnots.

◆ NbKnots()

int Geom_BSplineCurve::NbKnots ( ) const

Returns the number of knots. This method returns the number of knot without repetition of multiple knots.

◆ NbPoles()

int Geom_BSplineCurve::NbPoles ( ) const

Returns the number of poles.

◆ PeriodicNormalization()

void Geom_BSplineCurve::PeriodicNormalization ( double & U ) const

returns the parameter normalized within the period if the curve is periodic : otherwise does not do anything

◆ Pole()

const gp_Pnt & Geom_BSplineCurve::Pole ( const int Index ) const

Returns the pole of range Index. Raised if Index < 1 or Index > NbPoles.

◆ Poles() [1/2]

const NCollection_Array1< gp_Pnt > & Geom_BSplineCurve::Poles ( ) const

Returns the poles of the B-spline curve;.

◆ Poles() [2/2]

void Geom_BSplineCurve::Poles ( NCollection_Array1< gp_Pnt > & P ) const

Returns the poles of the B-spline curve;.

Raised if the length of P is not equal to the number of poles.

Deprecated: ("use Poles() returning const reference instead")

◆ RemoveKnot()

bool Geom_BSplineCurve::RemoveKnot	(	const int	Index,
		const int	M,
		const double	Tolerance )

Reduces the multiplicity of the knot of index Index to M. If M is equal to 0, the knot is removed. With a modification of this type, the array of poles is also modified. Two different algorithms are systematically used to compute the new poles of the curve. If, for each pole, the distance between the pole calculated using the first algorithm and the same pole calculated using the second algorithm, is less than Tolerance, this ensures that the curve is not modified by more than Tolerance. Under these conditions, true is returned; otherwise, false is returned. A low tolerance is used to prevent modification of the curve. A high tolerance is used to "smooth" the curve. Exceptions Standard_OutOfRange if Index is outside the bounds of the knots table. pole insertion and pole removing this operation is limited to the Uniform or QuasiUniform BSplineCurve. The knot values are modified. If the BSpline is NonUniform or Piecewise Bezier an exception Construction error is raised.

◆ Resolution()

void Geom_BSplineCurve::Resolution	(	const double	Tolerance3D,
		double &	UTolerance )

Computes for this BSpline curve the parametric tolerance UTolerance for a given 3D tolerance Tolerance3D. If f(t) is the equation of this BSpline curve, UTolerance ensures that: | t1 - t0| < Utolerance ===> |f(t1) - f(t0)| < Tolerance3D.

◆ Reverse()

void Geom_BSplineCurve::Reverse ( )

finalvirtual

Changes the direction of parametrization of <me>. The Knot sequence is modified, the FirstParameter and the LastParameter are not modified. The StartPoint of the initial curve becomes the EndPoint of the reversed curve and the EndPoint of the initial curve becomes the StartPoint of the reversed curve.

Implements Geom_Curve.

◆ ReversedParameter()

double Geom_BSplineCurve::ReversedParameter ( const double U ) const

finalvirtual

Returns the parameter on the reversed curve for the point of parameter U on <me>.

returns UFirst + ULast - U

Implements Geom_Curve.

◆ Segment()

void Geom_BSplineCurve::Segment	(	const double	U1,
		const double	U2,
		const double	theTolerance = Precision::PConfusion() )

Modifies this BSpline curve by segmenting it between U1 and U2. Either of these values can be outside the bounds of the curve, but U2 must be greater than U1. All data structure tables of this BSpline curve are modified, but the knots located between U1 and U2 are retained. The degree of the curve is not modified.

Parameter theTolerance defines the possible proximity of the segment boundaries and B-spline knots to treat them as equal.

Warnings : Even if <me> is not closed it can become closed after the segmentation for example if U1 or U2 are out of the bounds of the curve <me> or if the curve makes loop. After the segmentation the length of a curve can be null. raises if U2 < U1. Standard_DomainError if U2 - U1 exceeds the period for periodic curves. i.e. ((U2 - U1) - Period) > Precision::PConfusion().

◆ SetEvalRepresentation()

void Geom_BSplineCurve::SetEvalRepresentation ( const occ::handle< GeomEval_RepCurveDesc::Base > & theDesc )

Sets a new evaluation representation. Validates descriptor data and ensures no circular references.

◆ SetKnot() [1/2]

void Geom_BSplineCurve::SetKnot	(	const int	Index,
		const double	K )

Modifies this BSpline curve by assigning the value K to the knot of index Index in the knots table. This is a relatively local modification because K must be such that: Knots(Index - 1) < K < Knots(Index + 1) The second syntax allows you also to increase the multiplicity of the knot to M (but it is not possible to decrease the multiplicity of the knot with this function). Standard_ConstructionError if:

K is not such that: Knots(Index - 1) < K < Knots(Index + 1)
M is greater than the degree of this BSpline curve or lower than the previous multiplicity of knot of index Index in the knots table. Standard_OutOfRange if Index is outside the bounds of the knots table.

◆ SetKnot() [2/2]

void Geom_BSplineCurve::SetKnot	(	const int	Index,
		const double	K,
		const int	M )

Changes the knot of range Index with its multiplicity. You can increase the multiplicity of a knot but it is not allowed to decrease the multiplicity of an existing knot.

Raised if K >= Knots(Index+1) or K <= Knots(Index-1). Raised if M is greater than Degree or lower than the previous multiplicity of knot of range Index. Raised if Index < 1 || Index > NbKnots

◆ SetKnots()

void Geom_BSplineCurve::SetKnots ( const NCollection_Array1< double > & K )

Modifies this BSpline curve by assigning the array K to its knots table. The multiplicity of the knots is not modified. Exceptions Standard_ConstructionError if the values in the array K are not in ascending order. Standard_OutOfRange if the bounds of the array K are not respectively 1 and the number of knots of this BSpline curve.

◆ SetNotPeriodic()

void Geom_BSplineCurve::SetNotPeriodic ( )

Changes this BSpline curve into a non-periodic curve. If this curve is already non-periodic, it is not modified. Note: the poles and knots tables are modified. Warning If this curve is periodic, as the multiplicity of the first and last knots is not modified, and is not equal to Degree + 1, where Degree is the degree of this BSpline curve, the start and end points of the curve are not its first and last poles.

◆ SetOrigin() [1/2]

void Geom_BSplineCurve::SetOrigin	(	const double	U,
		const double	Tol )

Set the origin of a periodic curve at Knot U. If U is not a knot of the BSpline a new knot is inserted. KnotVector and poles are modified. Raised if the curve is not periodic.

◆ SetOrigin() [2/2]

void Geom_BSplineCurve::SetOrigin ( const int Index )

Assigns the knot of index Index in the knots table as the origin of this periodic BSpline curve. As a consequence, the knots and poles tables are modified. Exceptions Standard_NoSuchObject if this curve is not periodic. Standard_DomainError if Index is outside the bounds of the knots table.

◆ SetPeriodic()

void Geom_BSplineCurve::SetPeriodic ( )

Changes this BSpline curve into a periodic curve. To become periodic, the curve must first be closed. Next, the knot sequence must be periodic. For this, FirstUKnotIndex and LastUKnotIndex are used to compute I1 and I2, the indexes in the knots array of the knots corresponding to the first and last parameters of this BSpline curve. The period is therefore: Knots(I2) - Knots(I1). Consequently, the knots and poles tables are modified. Exceptions Standard_ConstructionError if this BSpline curve is not closed.

◆ SetPole() [1/2]

void Geom_BSplineCurve::SetPole	(	const int	Index,
		const gp_Pnt &	P )

Modifies this BSpline curve by assigning P to the pole of index Index in the poles table. Exceptions Standard_OutOfRange if Index is outside the bounds of the poles table. Standard_ConstructionError if Weight is negative or null.

◆ SetPole() [2/2]

void Geom_BSplineCurve::SetPole	(	const int	Index,
		const gp_Pnt &	P,
		const double	Weight )

Modifies this BSpline curve by assigning P to the pole of index Index in the poles table. This syntax also allows you to modify the weight of the modified pole, which becomes Weight. In this case, if this BSpline curve is non-rational, it can become rational and vice versa. Exceptions Standard_OutOfRange if Index is outside the bounds of the poles table. Standard_ConstructionError if Weight is negative or null.

◆ SetWeight()

void Geom_BSplineCurve::SetWeight	(	const int	Index,
		const double	Weight )

Changes the weight for the pole of range Index. If the curve was non rational it can become rational. If the curve was rational it can become non rational.

Raised if Index < 1 || Index > NbPoles Raised if Weight <= 0.0

◆ StartPoint()

gp_Pnt Geom_BSplineCurve::StartPoint ( ) const

finalvirtual

Returns the start point of the curve. Warnings : This point is different from the first pole of the curve if the multiplicity of the first knot is lower than Degree.

Implements Geom_BoundedCurve.

◆ Transform()

void Geom_BSplineCurve::Transform ( const gp_Trsf & T )

finalvirtual

Applies the transformation T to this BSpline curve.

Implements Geom_Geometry.

◆ updateKnots()

void Geom_BSplineCurve::updateKnots ( )

protected

Recompute the flatknots, the knotsdistribution, the continuity.

◆ Weight()

double Geom_BSplineCurve::Weight ( const int Index ) const

Returns the weight of the pole of range Index . Raised if Index < 1 or Index > NbPoles.

◆ Weights() [1/2]

const NCollection_Array1< double > * Geom_BSplineCurve::Weights ( ) const

Returns the weights of the B-spline curve;.

◆ Weights() [2/2]

void Geom_BSplineCurve::Weights ( NCollection_Array1< double > & W ) const

Returns the weights of the B-spline curve;.

Raised if the length of W is not equal to NbPoles.

Deprecated: ("use Weights() returning const pointer instead")

◆ WeightsArray()

const NCollection_Array1< double > & Geom_BSplineCurve::WeightsArray ( ) const

inline

Returns a const reference to the weights array. For rational curves: the internal owning weights array. For non-rational curves: a non-owning view of unit weights from BSplCLib. The array is always sized to match NbPoles().

Warning: Do NOT modify elements through the returned reference.

The documentation for this class was generated from the following file:

Geom_BSplineCurve.hxx

Public Member Functions

Static Public Member Functions

Protected Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ Geom_BSplineCurve() [1/3]

◆ Geom_BSplineCurve() [2/3]

◆ Geom_BSplineCurve() [3/3]

Member Function Documentation

◆ ClearEvalRepresentation()

◆ Continuity()

◆ Copy()

◆ Degree()

◆ DumpJson()

◆ EndPoint()

◆ EvalD0()

◆ EvalD1()

◆ EvalD2()

◆ EvalD3()

◆ EvalDN()

◆ EvalRepresentation()

◆ FirstParameter()

◆ FirstUKnotIndex()

◆ HasEvalRepresentation()

◆ IncreaseDegree()

◆ IncreaseMultiplicity() [1/2]

◆ IncreaseMultiplicity() [2/2]

◆ IncrementMultiplicity()

◆ InsertKnot()

◆ InsertKnots()

◆ IsClosed()

◆ IsCN()

◆ IsEqual()

◆ IsG1()

◆ IsPeriodic()

◆ IsRational()

◆ Knot()

◆ KnotDistribution()

◆ Knots() [1/2]

◆ Knots() [2/2]

◆ KnotSequence() [1/2]

◆ KnotSequence() [2/2]

◆ LastParameter()

◆ LastUKnotIndex()

◆ LocalD0()

◆ LocalD1()

◆ LocalD2()

◆ LocalD3()

◆ LocalDN()

◆ LocalValue()

◆ LocateU()

◆ MaxDegree()

◆ MovePoint()

◆ MovePointAndTangent()

◆ Multiplicities() [1/2]

◆ Multiplicities() [2/2]

◆ Multiplicity()

◆ NbKnots()

◆ NbPoles()

◆ PeriodicNormalization()

◆ Pole()

◆ Poles() [1/2]

◆ Poles() [2/2]

◆ RemoveKnot()

◆ Resolution()

◆ Reverse()

◆ ReversedParameter()

◆ Segment()

◆ SetEvalRepresentation()

◆ SetKnot() [1/2]

◆ SetKnot() [2/2]

◆ SetKnots()

◆ SetNotPeriodic()

◆ SetOrigin() [1/2]

◆ SetOrigin() [2/2]

◆ SetPeriodic()

◆ SetPole() [1/2]

◆ SetPole() [2/2]

◆ SetWeight()