Open CASCADE Technology 6.6.0
Public Member Functions
Geom2d_Curve Class Reference

The abstract class Curve describes the common
behavior of curves in 2D space. The Geom2d
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 Geom2d_Curve class shows:
More...

#include <Geom2d_Curve.hxx>

Inheritance diagram for Geom2d_Curve:
Inheritance graph
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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.

virtual Standard_Real ReversedParameter (const Standard_Real U) const =0
 Computes the parameter on the reversed curve for
the point of parameter U on this curve.
Note: The point of parameter U on this curve is
identical to the point of parameter
ReversedParameter(U) on the reversed curve.

virtual Standard_Real TransformedParameter (const Standard_Real U, const gp_Trsf2d &T) const
 Computes the parameter on the curve transformed by
T for the point of parameter U on this curve.
Note: this function generally returns U but it can be
redefined (for example, on a line).

virtual Standard_Real ParametricTransformation (const gp_Trsf2d &T) const
 Returns the coefficient required to compute the
parametric transformation of this curve when
transformation T is applied. This coefficient is the
ratio between the parameter of a point on this curve
and the parameter of the transformed point on the
new curve transformed by T.
Note: this function generally returns 1. but it can be
redefined (for example, on a line).

Handle_Geom2d_Curve Reversed () const
 Creates a reversed duplicate Changes the orientation of this curve. The first and
last parameters are not changed, but the parametric
direction of the curve is reversed.
If the curve is bounded:

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

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

virtual Standard_Boolean IsClosed () const =0
 Returns true if the curve is closed.
Examples :
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.

virtual Standard_Boolean IsPeriodic () const =0
 Returns true if the parameter of the curve is 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.

virtual Standard_Real Period () const
 Returns thne period of this curve.
//! raises if the curve is not periodic

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.

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.

virtual void D0 (const Standard_Real U, gp_Pnt2d &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.
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.

virtual void D1 (const Standard_Real U, gp_Pnt2d &P, gp_Vec2d &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.

virtual void D2 (const Standard_Real U, gp_Pnt2d &P, gp_Vec2d &V1, gp_Vec2d &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.

virtual void D3 (const Standard_Real U, gp_Pnt2d &P, gp_Vec2d &V1, gp_Vec2d &V2, gp_Vec2d &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.

virtual gp_Vec2d DN (const Standard_Real U, const Standard_Integer N) const =0
 For the point of parameter U of this curve, computes
the vector corresponding to the Nth derivative.
Exceptions
StdFail_UndefinedDerivative if:

gp_Pnt2d 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.


Detailed Description


Member Function Documentation

virtual GeomAbs_Shape Geom2d_Curve::Continuity ( ) const [pure virtual]
virtual void Geom2d_Curve::D0 ( const Standard_Real  U,
gp_Pnt2d P 
) const [pure virtual]
virtual void Geom2d_Curve::D1 ( const Standard_Real  U,
gp_Pnt2d P,
gp_Vec2d V1 
) const [pure virtual]
virtual void Geom2d_Curve::D2 ( const Standard_Real  U,
gp_Pnt2d P,
gp_Vec2d V1,
gp_Vec2d V2 
) const [pure virtual]
virtual void Geom2d_Curve::D3 ( const Standard_Real  U,
gp_Pnt2d P,
gp_Vec2d V1,
gp_Vec2d V2,
gp_Vec2d V3 
) const [pure virtual]
virtual gp_Vec2d Geom2d_Curve::DN ( const Standard_Real  U,
const Standard_Integer  N 
) const [pure virtual]
  • the continuity of the curve is not "CN", or
  • the derivative vector cannot be computed easily;
    this is the case with specific types of curve (for
    example, a rational BSpline curve where N is greater than 3).
    Standard_RangeError if N is less than 1.

Implemented in Geom2d_Line, Geom2d_Circle, Geom2d_Ellipse, Geom2d_Hyperbola, Geom2d_Parabola, Geom2d_BezierCurve, Geom2d_BSplineCurve, Geom2d_TrimmedCurve, Geom2d_OffsetCurve, Bisector_BisecAna, Bisector_BisecPC, and Bisector_BisecCC.

virtual Standard_Real Geom2d_Curve::FirstParameter ( ) const [pure virtual]
virtual Standard_Boolean Geom2d_Curve::IsClosed ( ) const [pure virtual]
virtual Standard_Boolean Geom2d_Curve::IsCN ( const Standard_Integer  N) const [pure virtual]
virtual Standard_Boolean Geom2d_Curve::IsPeriodic ( ) const [pure virtual]
virtual Standard_Real Geom2d_Curve::LastParameter ( ) const [pure virtual]
virtual Standard_Real Geom2d_Curve::ParametricTransformation ( const gp_Trsf2d T) const [virtual]
virtual Standard_Real Geom2d_Curve::Period ( ) const [virtual]

Reimplemented in Geom2d_TrimmedCurve, and Geom2d_OffsetCurve.

virtual void Geom2d_Curve::Reverse ( ) [pure virtual]
Handle_Geom2d_Curve Geom2d_Curve::Reversed ( ) const
  • the start point of the initial curve becomes the end
    point of the reversed curve, and
  • the end point of the initial curve becomes the start
    point of the reversed curve.
  • Reversed creates a new curve.
virtual Standard_Real Geom2d_Curve::ReversedParameter ( const Standard_Real  U) const [pure virtual]
virtual Standard_Real Geom2d_Curve::TransformedParameter ( const Standard_Real  U,
const gp_Trsf2d T 
) const [virtual]
gp_Pnt2d Geom2d_Curve::Value ( const Standard_Real  U) const

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