occt/src/Geom2d/Geom2d_OffsetCurve.hxx

// Created on: 1993-03-24
// Created by: Philippe DAUTRY
// Copyright (c) 1993-1999 Matra Datavision
// Copyright (c) 1999-2014 OPEN CASCADE SAS
//
// This file is part of Open CASCADE Technology software library.
//
// This library is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License version 2.1 as published
// by the Free Software Foundation, with special exception defined in the file
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
// distribution for complete text of the license and disclaimer of any warranty.
//
// Alternatively, this file may be used under the terms of Open CASCADE
// commercial license or contractual agreement.

#ifndef _Geom2d_OffsetCurve_HeaderFile
#define _Geom2d_OffsetCurve_HeaderFile

#include <Standard.hxx>
#include <Standard_Type.hxx>

#include <Standard_Real.hxx>
#include <GeomAbs_Shape.hxx>
#include <Geom2d_Curve.hxx>
#include <Standard_Boolean.hxx>
#include <Standard_Integer.hxx>
class Geom2d_Curve;
class Standard_ConstructionError;
class Standard_RangeError;
class Standard_NoSuchObject;
class Geom2d_UndefinedDerivative;
class Geom2d_UndefinedValue;
class Standard_NotImplemented;
class gp_Pnt2d;
class gp_Vec2d;
class gp_Trsf2d;
class Geom2d_Geometry;


class Geom2d_OffsetCurve;
DEFINE_STANDARD_HANDLE(Geom2d_OffsetCurve, Geom2d_Curve)


//! This class implements the basis services for the creation,
//! edition, modification and evaluation of planar offset curve.
//! The offset curve is obtained by offsetting by distance along
//! the normal to a basis curve defined in 2D space.
//! The offset curve in this package can be a self intersecting
//! curve even if the basis curve does not self-intersect.
//! The self intersecting portions are not deleted at the
//! construction time.
//! An offset curve is a curve at constant distance (Offset) from a
//! basis curve and the offset curve takes its parametrization from
//! the basis curve. The Offset curve is in the direction of the
//! normal to the basis curve N.
//! The distance offset may be positive or negative to indicate the
//! preferred side of the curve :
//! . distance offset >0 => the curve is in the direction of N
//! . distance offset >0 => the curve is in the direction of - N
//! On the Offset curve :
//! Value(u) = BasisCurve.Value(U) + (Offset * (T ^ Z)) / ||T ^ Z||
//! where T is the tangent vector to the basis curve and Z the
//! direction of the normal vector to the plane of the curve,
//! N = T ^ Z defines the offset direction and should not have
//! null length.
//!
//! Warnings :
//! In this package we suppose that the continuity of the offset
//! curve is one degree less than the continuity of the
//! basis curve and we don't check that at any point ||T^Z|| != 0.0
//!
//! So to evaluate the curve it is better to check that the offset
//! curve is well defined at any point because an exception could
//! be raised. The check is not done in this package at the creation
//! of the offset curve because the control needs the use of an
//! algorithm which cannot be implemented in this package.
//! The OffsetCurve is closed if the first point and the last point
//! are the same (The distance between these two points is lower or
//! equal to the Resolution sea package gp) . The OffsetCurve can be
//! closed even if the basis curve is not closed.
class Geom2d_OffsetCurve : public Geom2d_Curve
{

public:

  
  //! Constructs a curve offset from the basis curve C,
  //! where Offset is the distance between the offset
  //! curve and the basis curve at any point.
  //! A point on the offset curve is built by measuring the
  //! offset value along a normal vector at a point on C.
  //! This normal vector is obtained by rotating the
  //! vector tangential to C at 90 degrees in the
  //! anti-trigonometric sense. The side of C on which
  //! the offset value is measured is indicated by this
  //! normal vector if Offset is positive, or in the inverse
  //! sense if Offset is negative.
  //! If isNotCheckC0 = TRUE checking if basis curve has C0-continuity
  //! is not made.
  //! Warnings :
  //! In this package the entities are not shared. The OffsetCurve is
  //! built with a copy of the curve C. So when C is modified the
  //! OffsetCurve is not modified
  //! Warning!  if isNotCheckC0 = false,
  //! ConstructionError  raised if the basis curve C is not at least C1.
  //! No check is done to know if ||V^Z|| != 0.0 at any point.
  Standard_EXPORT Geom2d_OffsetCurve(const Handle(Geom2d_Curve)& C, const Standard_Real Offset, const Standard_Boolean isNotCheckC0 = Standard_False);
  
  //! Changes the direction of parametrization of <me>.
  //! As a result:
  //! - the basis curve is reversed,
  //! - the start point of the initial curve becomes the end
  //! point of the reversed curve,
  //! - the end point of the initial curve becomes the start
  //! point of the reversed curve, and
  //! - the first and last parameters are recomputed.
  Standard_EXPORT void Reverse();
  
  //! Computes the parameter on the reversed curve for
  //! the point of parameter U on this offset curve.
  Standard_EXPORT Standard_Real ReversedParameter (const Standard_Real U) const;
  
  //! Changes this offset curve by assigning C as the
  //! basis curve from which it is built.
  //! If isNotCheckC0 = TRUE checking if basis curve has C0-continuity
  //! is not made.
  //! Exceptions
  //! if isNotCheckC0 = false,
  //! Standard_ConstructionError if the curve C is not at least "C1" continuous.
  Standard_EXPORT void SetBasisCurve (const Handle(Geom2d_Curve)& C, const Standard_Boolean isNotCheckC0 = Standard_False);
  
  //! Changes this offset curve by assigning D as the offset value.
  Standard_EXPORT void SetOffsetValue (const Standard_Real D);
  
  //! Returns the basis curve of this offset curve. The basis curve can be an offset curve.
  Standard_EXPORT Handle(Geom2d_Curve) BasisCurve() const;
  

  //! Continuity of the Offset 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.
  //! Warnings :
  //! Returns the continuity of the basis curve - 1.
  //! The offset curve must have a unique normal direction defined
  //! at any point.
  //! Value and derivatives
  //!
  //! Warnings :
  //! The exception UndefinedValue or UndefinedDerivative is
  //! raised if it is not possible to compute a unique offset
  //! direction.
  //! If T is the first derivative with not null length and
  //! Z the direction normal to the plane of the curve, the
  //! relation ||T(U) ^ Z|| != 0  must be satisfied to evaluate
  //! the offset curve.
  //! No check is done at the creation time and we suppose
  //! in this package that the offset curve is well defined.
  Standard_EXPORT GeomAbs_Shape Continuity() const;
  
  //! Warning! this should not be called
  //! if the basis curve is not at least C1. Nevertheless
  //! if used on portion where the curve is C1, it is OK
  Standard_EXPORT void D0 (const Standard_Real U, gp_Pnt2d& P) const;
  
  //! Warning! this should not be called
  //! if the continuity of the basis curve is not C2.
  //! Nevertheless, it's OK to use it  on portion
  //! where the curve is C2
  Standard_EXPORT void D1 (const Standard_Real U, gp_Pnt2d& P, gp_Vec2d& V1) const;
  
  //! Warning!  This  should  not  be called
  //! if the continuity of the basis curve is not C3.
  //! Nevertheless, it's OK to use it  on portion
  //! where the curve is C3
  Standard_EXPORT void D2 (const Standard_Real U, gp_Pnt2d& P, gp_Vec2d& V1, gp_Vec2d& V2) const;
  
  //! Warning! This should not be called
  //! if the continuity of the basis curve is not C4.
  //! Nevertheless, it's OK to use it  on portion
  //! where the curve is C4
  Standard_EXPORT void D3 (const Standard_Real U, gp_Pnt2d& P, gp_Vec2d& V1, gp_Vec2d& V2, gp_Vec2d& V3) const;
  
  //! The returned vector gives the value of the derivative
  //! for the order of derivation N.
  //! Warning! this should not be called
  //! raises  UndefunedDerivative   if the continuity of the basis curve is not CN+1.
  //! Nevertheless, it's OK to use it  on portion
  //! where the curve is CN+1
  //! raises  RangeError if N < 1.
  //! raises  NotImplemented if N > 3.
  //! The following functions compute the value and derivatives
  //! on the offset curve and returns the derivatives on the
  //! basis curve too.
  //! The computation of the value and derivatives on the basis
  //! curve are used to evaluate the offset curve
  //! Warnings :
  //! The exception UndefinedValue or UndefinedDerivative is
  //! raised if it is not possible to compute a unique offset direction.
  Standard_EXPORT gp_Vec2d DN (const Standard_Real U, const Standard_Integer N) const;
  
  //! Warning! this should not be called
  //! if the basis curve is not at least C1. Nevertheless
  //! if used on portion where the curve is C1, it is OK
  Standard_EXPORT void Value (const Standard_Real U, gp_Pnt2d& P, gp_Pnt2d& Pbasis, gp_Vec2d& V1basis) const;
  
  //! Warning! this should not be called
  //! if the continuity of the basis curve is not C1.
  //! Nevertheless, it's OK to use it  on portion
  //! where the curve is C1
  Standard_EXPORT void D1 (const Standard_Real U, gp_Pnt2d& P, gp_Pnt2d& Pbasis, gp_Vec2d& V1, gp_Vec2d& V1basis, gp_Vec2d& V2basis) const;
  
  //! Warning! this should not be called
  //! if the continuity of the basis curve is not C3.
  //! Nevertheless, it's OK to use it  on portion
  //! where the curve is C3
  Standard_EXPORT void D2 (const Standard_Real U, gp_Pnt2d& P, gp_Pnt2d& Pbasis, gp_Vec2d& V1, gp_Vec2d& V2, gp_Vec2d& V1basis, gp_Vec2d& V2basis, gp_Vec2d& V3basis) const;
  
  Standard_EXPORT Standard_Real FirstParameter() const;
  
  //! Returns the value of the first or last parameter of this
  //! offset curve. The first parameter corresponds to the
  //! start point of the curve. The last parameter
  //! corresponds to the end point.
  //! Note: the first and last parameters of this offset curve
  //! are also the ones of its basis curve.
  Standard_EXPORT Standard_Real LastParameter() const;
  
  //! Returns the offset value of this offset curve.
  Standard_EXPORT Standard_Real Offset() const;
  

  //! Returns True if the distance between the start point
  //! and the end point of the curve is lower or equal to
  //! Resolution from package gp.
  Standard_EXPORT Standard_Boolean IsClosed() const;
  
  //! Is the order of continuity of the curve N ?
  //! Warnings :
  //! This method answer True if the continuity of the basis curve
  //! is N + 1.  We suppose in this class that a normal direction
  //! to the basis curve (used to compute the offset curve) is
  //! defined at any point on the basis curve.
  //! Raised if N < 0.
  Standard_EXPORT Standard_Boolean IsCN (const Standard_Integer N) const;
  
  //! Is the parametrization of a curve is periodic ?
  //! If the basis curve is a circle or an ellipse the corresponding
  //! OffsetCurve is periodic. If the basis curve can't be periodic
  //! (for example BezierCurve) the OffsetCurve can't be periodic.
  Standard_EXPORT Standard_Boolean IsPeriodic() const;
  
  //! Returns the period of this offset curve, i.e. the period
  //! of the basis curve of this offset curve.
  //! Exceptions
  //! Standard_NoSuchObject if the basis curve is not periodic.
  Standard_EXPORT virtual Standard_Real Period() const Standard_OVERRIDE;
  
  //! Applies the transformation T to this offset curve.
  //! Note: the basis curve is also modified.
  Standard_EXPORT void Transform (const gp_Trsf2d& T);
  
  //! 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 calls the basis curve method.
  Standard_EXPORT virtual Standard_Real TransformedParameter (const Standard_Real U, const gp_Trsf2d& T) const Standard_OVERRIDE;
  
  //! 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 calls the basis curve method.
  Standard_EXPORT virtual Standard_Real ParametricTransformation (const gp_Trsf2d& T) const Standard_OVERRIDE;
  
  //! Creates a new object, which is a copy of this offset curve.
  Standard_EXPORT Handle(Geom2d_Geometry) Copy() const;
  
  //! Returns continuity of the basis curve.
  Standard_EXPORT GeomAbs_Shape GetBasisCurveContinuity() const;




  DEFINE_STANDARD_RTTI(Geom2d_OffsetCurve,Geom2d_Curve)

protected:




private:


  Handle(Geom2d_Curve) basisCurve;
  Standard_Real offsetValue;
  GeomAbs_Shape myBasisCurveContinuity;


};







#endif // _Geom2d_OffsetCurve_HeaderFile