Open CASCADE Technology  7.3.1.dev
Geom_Curve Class Referenceabstract

The abstract class Curve describes the common behavior of curves in 3D space. The Geom package provides numerous concrete classes of derived curves, including lines, circles, conics, Bezier or BSpline curves, etc. The main characteristic of these curves is that they are parameterized. The Geom_Curve class shows: More...

`#include <Geom_Curve.hxx>`

Inheritance diagram for Geom_Curve: [legend]

## Public Member Functions

virtual void Reverse ()=0
Changes the direction of parametrization of <me>. The "FirstParameter" and the "LastParameter" are not changed but the orientation of the curve is modified. If the curve is bounded 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. More...

virtual Standard_Real ReversedParameter (const Standard_Real U) const =0
Returns the parameter on the reversed curve for the point of parameter U on <me>. More...

virtual Standard_Real TransformedParameter (const Standard_Real U, const gp_Trsf &T) const
Returns the parameter on the transformed curve for the transform of the point of parameter U on <me>. More...

virtual Standard_Real 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>. More...

Handle< Geom_CurveReversed () const
Returns a copy of <me> reversed. More...

virtual Standard_Real FirstParameter () const =0
Returns the value of the first parameter. Warnings : It can be RealFirst from package Standard if the curve is infinite. More...

virtual Standard_Real LastParameter () const =0
Returns the value of the last parameter. Warnings : It can be RealLast from package Standard if the curve is infinite. More...

virtual Standard_Boolean IsClosed () const =0
Returns true if the curve is closed. Some curves such as circle are always closed, others such as line are never closed (by definition). Some Curves such as OffsetCurve can be closed or not. These curves are considered as closed if the distance between the first point and the last point of the curve is lower or equal to the Resolution from package gp wich is a fixed criterion independant of the application. More...

virtual Standard_Boolean IsPeriodic () const =0
Is the parametrization of the curve periodic ? It is possible only if the curve is closed and if the following relation is satisfied : for each parametric value U the distance between the point P(u) and the point P (u + T) is lower or equal to Resolution from package gp, T is the period and must be a constant. There are three possibilities : . the curve is never periodic by definition (SegmentLine) . the curve is always periodic by definition (Circle) . the curve can be defined as periodic (BSpline). In this case a function SetPeriodic allows you to give the shape of the curve. The general rule for this case is : if a curve can be periodic or not the default periodicity set is non periodic and you have to turn (explicitly) the curve into a periodic curve if you want the curve to be periodic. More...

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

virtual GeomAbs_Shape Continuity () const =0
It is 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, G1 : tangency continuity all along the Curve, G2 : curvature continuity all along the Curve, CN : the order of continuity is infinite. More...

virtual Standard_Boolean IsCN (const Standard_Integer N) const =0
Returns true if the degree of continuity of this curve is at least N. Exceptions - Standard_RangeError if N is less than 0. More...

virtual void D0 (const Standard_Real U, gp_Pnt &P) const =0
Returns in P the point of parameter U. If the curve is periodic then the returned point is P(U) with U = Ustart + (U - Uend) where Ustart and Uend are the parametric bounds of the curve. More...

virtual void D1 (const Standard_Real U, gp_Pnt &P, gp_Vec &V1) const =0
Returns the point P of parameter U and the first derivative V1. Raised if the continuity of the curve is not C1. More...

virtual void D2 (const Standard_Real U, gp_Pnt &P, gp_Vec &V1, gp_Vec &V2) const =0
Returns the point P of parameter U, the first and second derivatives V1 and V2. Raised if the continuity of the curve is not C2. More...

virtual void D3 (const Standard_Real U, gp_Pnt &P, gp_Vec &V1, gp_Vec &V2, gp_Vec &V3) const =0
Returns the point P of parameter U, the first, the second and the third derivative. Raised if the continuity of the curve is not C3. More...

virtual gp_Vec DN (const Standard_Real U, const Standard_Integer N) const =0
The returned vector gives the value of the derivative for the order of derivation N. Raised if the continuity of the curve is not CN. More...

gp_Pnt Value (const Standard_Real U) const
Computes the point of parameter U on <me>. If the curve is periodic then the returned point is P(U) with U = Ustart + (U - Uend) where Ustart and Uend are the parametric bounds of the curve. it is implemented with D0. More... 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. More...

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. More...

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). More...

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

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

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

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

virtual void Transform (const gp_Trsf &T)=0
Transformation of a geometric object. This tansformation can be a translation, a rotation, a symmetry, a scaling or a complex transformation obtained by combination of the previous elementaries transformations. (see class Transformation of the package Geom). More...

Handle< Geom_GeometryMirrored (const gp_Pnt &P) const

Handle< Geom_GeometryMirrored (const gp_Ax1 &A1) const

Handle< Geom_GeometryMirrored (const gp_Ax2 &A2) const

Handle< Geom_GeometryRotated (const gp_Ax1 &A1, const Standard_Real Ang) const

Handle< Geom_GeometryScaled (const gp_Pnt &P, const Standard_Real S) const

Handle< Geom_GeometryTransformed (const gp_Trsf &T) const

Handle< Geom_GeometryTranslated (const gp_Vec &V) const

Handle< Geom_GeometryTranslated (const gp_Pnt &P1, const gp_Pnt &P2) const

virtual Handle< Geom_GeometryCopy () const =0
Creates a new object which is a copy of this geometric object. More... Public Member Functions inherited from Standard_Transient
Standard_Transient ()
Empty constructor. More...

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

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

virtual ~Standard_Transient ()
Destructor must be virtual. More...

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

virtual const opencascade::handle< Standard_Type > & DynamicType () const

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

Standard_Boolean IsInstance (const Standard_CString theTypeName) const
Returns a true value if this is an instance of TypeName. More...

Standard_Boolean 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. More...

Standard_Boolean IsKind (const Standard_CString 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. More...

Standard_TransientThis () 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. More...

Standard_Integer GetRefCount () const
Get the reference counter of this object. More...

void IncrementRefCounter () const
Increments the reference counter of this object. More...

Standard_Integer DecrementRefCounter () const
Decrements the reference counter of this object; returns the decremented value. More...

## Additional Inherited Members Public Types inherited from Standard_Transient
typedef void base_type Static Public Member Functions inherited from Standard_Transient
static const char * get_type_name ()

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

## Detailed Description

The abstract class Curve describes the common behavior of curves in 3D space. The Geom package provides numerous concrete classes of derived curves, including lines, circles, conics, Bezier or BSpline curves, etc. The main characteristic of these curves is that they are parameterized. The Geom_Curve class shows:

• how to work with the parametric equation of a curve in order to calculate the point of parameter u, together with the vector tangent and the derivative vectors of order 2, 3,..., N at this point;
• how to obtain general information about the curve (for example, level of continuity, closed characteristics, periodicity, bounds of the parameter field);
• how the parameter changes when a geometric transformation is applied to the curve or when the orientation of the curve is inverted. All curves must have a geometric continuity: a curve is at least "C0". Generally, this property is checked at the time of construction or when the curve is edited. Where this is not the case, the documentation states so explicitly. Warning The Geom package does not prevent the construction of curves with null length or curves which self-intersect.

## ◆ Continuity()

 virtual GeomAbs_Shape Geom_Curve::Continuity ( ) const
pure virtual

It is 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, G1 : tangency continuity all along the Curve, G2 : curvature continuity all along the Curve, CN : the order of continuity is infinite.

## ◆ D0()

 virtual void Geom_Curve::D0 ( const Standard_Real U, gp_Pnt & P ) const
pure virtual

Returns in P the point of parameter U. If the curve is periodic then the returned point is P(U) with U = Ustart + (U - Uend) where Ustart and Uend are the parametric bounds of the curve.

Raised only for the "OffsetCurve" if it is not possible to compute the current point. For example when the first derivative on the basis curve and the offset direction are parallel.

## ◆ D1()

 virtual void Geom_Curve::D1 ( const Standard_Real U, gp_Pnt & P, gp_Vec & V1 ) const
pure virtual

Returns the point P of parameter U and the first derivative V1. Raised if the continuity of the curve is not C1.

## ◆ D2()

 virtual void Geom_Curve::D2 ( const Standard_Real U, gp_Pnt & P, gp_Vec & V1, gp_Vec & V2 ) const
pure virtual

Returns the point P of parameter U, the first and second derivatives V1 and V2. Raised if the continuity of the curve is not C2.

## ◆ D3()

 virtual void Geom_Curve::D3 ( const Standard_Real U, gp_Pnt & P, gp_Vec & V1, gp_Vec & V2, gp_Vec & V3 ) const
pure virtual

Returns the point P of parameter U, the first, the second and the third derivative. Raised if the continuity of the curve is not C3.

## ◆ DN()

 virtual gp_Vec Geom_Curve::DN ( const Standard_Real U, const Standard_Integer N ) const
pure virtual

The returned vector gives the value of the derivative for the order of derivation N. Raised if the continuity of the curve is not CN.

Raised if the derivative cannot be computed easily. e.g. rational bspline and n > 3. Raised if N < 1.

## ◆ FirstParameter()

 virtual Standard_Real Geom_Curve::FirstParameter ( ) const
pure virtual

Returns the value of the first parameter. Warnings : It can be RealFirst from package Standard if the curve is infinite.

## ◆ IsClosed()

 virtual Standard_Boolean Geom_Curve::IsClosed ( ) const
pure virtual

Returns true if the curve is closed. Some curves such as circle are always closed, others such as line are never closed (by definition). Some Curves such as OffsetCurve can be closed or not. These curves are considered as closed if the distance between the first point and the last point of the curve is lower or equal to the Resolution from package gp wich is a fixed criterion independant of the application.

## ◆ IsCN()

 virtual Standard_Boolean Geom_Curve::IsCN ( const Standard_Integer N ) const
pure virtual

Returns true if the degree of continuity of this curve is at least N. Exceptions - Standard_RangeError if N is less than 0.

## ◆ IsPeriodic()

 virtual Standard_Boolean Geom_Curve::IsPeriodic ( ) const
pure virtual

Is the parametrization of the curve periodic ? It is possible only if the curve is closed and if the following relation is satisfied : for each parametric value U the distance between the point P(u) and the point P (u + T) is lower or equal to Resolution from package gp, T is the period and must be a constant. There are three possibilities : . the curve is never periodic by definition (SegmentLine) . the curve is always periodic by definition (Circle) . the curve can be defined as periodic (BSpline). In this case a function SetPeriodic allows you to give the shape of the curve. The general rule for this case is : if a curve can be periodic or not the default periodicity set is non periodic and you have to turn (explicitly) the curve into a periodic curve if you want the curve to be periodic.

## ◆ LastParameter()

 virtual Standard_Real Geom_Curve::LastParameter ( ) const
pure virtual

Returns the value of the last parameter. Warnings : It can be RealLast from package Standard if the curve is infinite.

## ◆ ParametricTransformation()

 virtual Standard_Real Geom_Curve::ParametricTransformation ( const gp_Trsf & T ) const
virtual

Returns a coefficient to compute the parameter on the transformed curve for the transform of the point on <me>.

Transformed(T)->Value(U * ParametricTransformation(T))

is the same point as

Value(U).Transformed(T)

This methods returns 1.

It can be redefined. For example on the Line.

Reimplemented in Geom_OffsetCurve, Geom_TrimmedCurve, Geom_Parabola, and Geom_Line.

## ◆ Period()

 virtual Standard_Real Geom_Curve::Period ( ) const
virtual

Returns the period of this curve. Exceptions Standard_NoSuchObject if this curve is not periodic.

Reimplemented in Geom_OffsetCurve, and Geom_TrimmedCurve.

## ◆ Reverse()

 virtual void Geom_Curve::Reverse ( )
pure virtual

Changes the direction of parametrization of <me>. The "FirstParameter" and the "LastParameter" are not changed but the orientation of the curve is modified. If the curve is bounded 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.

Implemented in Geom_BSplineCurve, Geom_BezierCurve, Geom_Conic, Geom_OffsetCurve, Geom_TrimmedCurve, and Geom_Line.

## ◆ Reversed()

 Handle< Geom_Curve > Geom_Curve::Reversed ( ) const

Returns a copy of <me> reversed.

## ◆ ReversedParameter()

 virtual Standard_Real Geom_Curve::ReversedParameter ( const Standard_Real U ) const
pure virtual

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

me->Reversed()->Value(me->ReversedParameter(U))

is the same point as

me->Value(U)

## ◆ TransformedParameter()

 virtual Standard_Real Geom_Curve::TransformedParameter ( const Standard_Real U, const gp_Trsf & T ) const
virtual

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

me->Transformed(T)->Value(me->TransformedParameter(U,T))

is the same point as

me->Value(U).Transformed(T)

This methods returns <U>

It can be redefined. For example on the Line.

Reimplemented in Geom_OffsetCurve, Geom_TrimmedCurve, Geom_Parabola, and Geom_Line.

## ◆ Value()

 gp_Pnt Geom_Curve::Value ( const Standard_Real U ) const

Computes the point of parameter U on <me>. If the curve is periodic then the returned point is P(U) with U = Ustart + (U - Uend) where Ustart and Uend are the parametric bounds of the curve. it is implemented with D0.

Raised only for the "OffsetCurve" if it is not possible to compute the current point. For example when the first derivative on the basis curve and the offset direction are parallel.

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