[occt.git] / src / Geom2d / Geom2d_BSplineCurve.cdl

-- Created on: 1993-03-24
-- Created by: JCV
-- 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.

-- xab : modified 15-Mar-95 : added cache mecanism to speed up
-- evaluation


class BSplineCurve from Geom2d inherits BoundedCurve from Geom2d

        --- Purpose : Describes a BSpline curve.
    	-- A BSpline curve can be:
    	-- - uniform or non-uniform,
    	-- - rational or non-rational,
    	-- - periodic or non-periodic.
    	-- A BSpline curve is defined by:
    	-- - its degree; the degree for a
    	--   Geom2d_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 they 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
    	--   Geom2d_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, such that:
    	-- - 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.
      	-- Warnings :
        --  In this class we consider that a weight value is zero if
        --  Weight <= Resolution from package gp.
        --  For two parametric values (or two knot values) U1, U2 we 
        --  consider that U1 = U2 if Abs (U2 - U1) <= Epsilon (U1).
        --  For two weights values W1, W2 we consider that W1 = W2 if
        --  Abs (W2 - W1) <= Epsilon (W1).  The method Epsilon is
        --  defined in the class Real from package Standard.
        --  
        -- 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


uses  Array1OfInteger      from TColStd,
      Array1OfReal         from TColStd,
      HArray1OfInteger     from TColStd,
      HArray1OfReal        from TColStd,
      Array1OfPnt2d        from TColgp,
      Ax2d                 from gp, 
      Pnt2d                from gp,
      HArray1OfPnt2d       from TColgp,
      Trsf2d               from gp,
      Vec2d                from gp,
      BSplKnotDistribution from GeomAbs,
      Geometry             from Geom2d,
      Shape                from GeomAbs,
      Mutex                from Standard

raises ConstructionError   from Standard,
       DimensionError      from Standard,
       DomainError         from Standard,
       OutOfRange          from Standard,
       RangeError          from Standard,
       NoSuchObject        from Standard,
       UndefinedDerivative from Geom2d

is


  Create (Poles          : Array1OfPnt2d   from TColgp; 
          Knots          : Array1OfReal    from TColStd; 
          Multiplicities : Array1OfInteger from TColStd; 
          Degree         : Integer;
    	  Periodic       : Boolean = Standard_False)
	  
  returns BSplineCurve from Geom2d

        ---Purpose :  Creates a  non-rational B_spline curve   on  the
        --         basis <Knots, Multiplicities> of degree <Degree>.
    	-- The following conditions must be verified.
        --  0 < Degree <= MaxDegree.
        --  
        --  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 recommanded 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

  raises ConstructionError;

    	
  Create (Poles          : Array1OfPnt2d   from TColgp; 
    	  Weights        : Array1OfReal    from TColStd;
          Knots          : Array1OfReal    from TColStd; 
          Multiplicities : Array1OfInteger from TColStd; 
          Degree         : Integer;
    	  Periodic       : Boolean = Standard_False)
	  
  returns BSplineCurve from Geom2d

        ---Purpose : Creates  a rational B_spline  curve  on the basis
        --         <Knots, Multiplicities> of degree <Degree>.
    	-- The following conditions must be verified.
        --  0 < Degree <= MaxDegree.
        --  
        --  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 recommanded 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

  raises ConstructionError;

   
  IncreaseDegree (me : mutable; Degree : Integer)
  
        ---Purpose: 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
    	-- Geom2d_BSplineCurve::MaxDegree().
  raises ConstructionError;
       

 IncreaseMultiplicity (me : mutable; Index : Integer; M : Integer)
 
        ---Purpose :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.

 raises OutOfRange;
    	
	---Purpose: If <Index> is not in [FirstUKnotIndex, LastUKnotIndex]


  IncreaseMultiplicity (me : mutable; I1, I2 : Integer; M : Integer) 
  
        ---Purpose :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.
    	-- As a result, the poles and weights tables of this curve are modified.
    	-- Warning
    	-- It is forbidden to modify the multiplicity of the first or
    	-- last knot of a non-periodic curve. Be careful as
    	-- Geom2d does not protect against this.
    	-- Exceptions
    	-- Standard_OutOfRange if either Index, I1 or I2 is
    	-- outside the bounds of the knots table.
 raises OutOfRange;
    	

  IncrementMultiplicity (me : mutable; I1, I2 : Integer; M : Integer) 
  
        ---Purpose : Increases by M the multiplicity of the knots of indexes
    	-- I1 to I2 in the knots table of this BSpline curve. For
    	-- each knot, the resulting multiplicity is limited to the
    	-- degree of this curve. If M is negative, nothing is done.
    	-- As a result, the poles and weights tables of this
    	-- BSpline curve are modified.
    	-- Warning
    	-- It is forbidden to modify the multiplicity of the first or
    	-- last knot of a non-periodic curve. Be careful as
    	-- Geom2d does not protect against this.
    	-- Exceptions
    	-- Standard_OutOfRange if I1 or I2 is outside the
    	-- bounds of the knots table.

 raises OutOfRange;
    	

  InsertKnot (me : mutable; 
    	      U : Real; 
    	      M : Integer = 1; 
    	      ParametricTolerance : Real = 0.0); 
  
        ---Purpose: Inserts a knot value in the sequence of knots.  If
        --          <U>  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.
    	-- Warning
    	-- - If U is less than the first parameter or greater than
    	--   the last parameter of this BSpline curve, nothing is done.
    	-- - If M is negative or null, nothing is done.
    	-- - The multiplicity of a knot is limited to the degree of
    	--   this BSpline curve.
  

  InsertKnots (me : mutable; Knots : Array1OfReal    from TColStd; 
    	    	    	     Mults : Array1OfInteger from TColStd;
    	    	    	     ParametricTolerance : Real = 0.0;
      	    	    	     Add : Boolean = Standard_False);
			     
        ---Purpose: Inserts the values of the array Knots, with the
    	-- respective multiplicities given by the array Mults, into
    	-- the knots table of this BSpline curve.
    	-- If a value of the array Knots is an existing knot, its multiplicity is:
    	-- - increased by M, if Add is true, or
    	-- - increased to M, if Add is false (default value).
    	-- The tolerance criterion used for knot equality is the
	-- larger of the values ParametricTolerance (defaulted
    	-- to 0.) and Standard_Real::Epsilon(U),
    	-- where U is the current knot value.
    	-- Warning
    	-- - For a value of the array Knots which is less than
    	--   the first parameter or greater than the last
    	--   parameter of this BSpline curve, nothing is done.
    	-- - For a value of the array Mults which is negative or
    	--   null, nothing is done.
    	-- - The multiplicity of a knot is limited to the degree of
    	--   this BSpline curve.
			     

  RemoveKnot(me : mutable; Index     : Integer; 
    	    	    	   M         : Integer;
    	    	    	   Tolerance : Real) returns Boolean
			   
        ---Purpose : 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.
     raises OutOfRange;
     

  InsertPoleAfter (me : mutable; Index : Integer; P : Pnt2d;
    	    	   Weight : Real = 1.0)
        --- Purpose :
        --  The new pole is inserted after the pole of range Index.
        --  If the curve was non rational it can become rational.
     raises ConstructionError,
        --- Purpose :
        --  Raised if the B-spline is NonUniform or PiecewiseBezier or if
        --  Weight <= 0.0
            OutOfRange;
        --- Purpose : Raised if Index is not in the range [1, Number of Poles]


  InsertPoleBefore (me : mutable; Index : Integer; P : Pnt2d; 
    	    	    Weight : Real  =  1.0)
        --- Purpose :
        --  The new pole is inserted before the pole of range Index.
        --  If the curve was non rational it can become rational.
     raises ConstructionError,
        --- Purpose :
        --  Raised if the B-spline is NonUniform or PiecewiseBezier or if
        --  Weight <= 0.0
            OutOfRange;
        --- Purpose : Raised if Index is not in the range [1, Number of Poles]


  RemovePole (me : mutable; Index : Integer)
        --- Purpose :
        --  Removes the pole of range Index
        --  If the curve was rational it can become non rational.
     raises ConstructionError,
        --- Purpose :
        --  Raised if the B-spline is NonUniform or PiecewiseBezier.
        --  Raised if the number of poles of the B-spline curve is lower or 
        --  equal to 2 before removing.
            OutOfRange;
        --- Purpose : Raised if Index is not in the range [1, Number of Poles]

  Reverse (me : mutable);
        --- Purpose : Reverses the orientation of this BSpline curve. As a result
    	-- - the knots and poles tables are modified;
    	-- - 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.
        

  ReversedParameter(me; U : Real) returns Real;
    	---Purpose: Computes the parameter on the reversed curve for
    	-- the point of parameter U on this BSpline curve.
    	-- The returned value is: UFirst + ULast - U,
    	-- where UFirst and ULast are the values of the
    	-- first and last parameters of this BSpline curve.


  Segment (me : mutable; U1, U2 : Real)
        ---Purpose : 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.
        -- 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.
    	--        - The segmentation of a periodic curve over an
    	---   interval corresponding to its period generates a
    	--  non-periodic curve with equivalent geometry.
      	--  Exceptions
    	-- Standard_DomainError if U2 is less than U1.
    raises DomainError from Standard;
	---Purpose: raises if U2 < U1.


  SetKnot (me : mutable; Index : Integer; K : Real)
	--- Purpose :  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)
    	-- Exceptions
    	-- 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.
     raises ConstructionError,
	            OutOfRange;


  SetKnots (me : mutable; K : Array1OfReal from TColStd)
    	--- Purpose :  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.
     raises ConstructionError,
	            OutOfRange;
      

  SetKnot (me : mutable; Index : Integer; K : Real; M : Integer)
	--- Purpose : 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).
    	-- Exceptions
    	-- 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.
     raises ConstructionError,
	            OutOfRange;

  PeriodicNormalization(me ;  U : in out Real) ; 
       
        ---Purpose : Computes the parameter normalized within the
    	-- "first" period of this BSpline curve, if it is periodic:
    	-- the returned value is in the range Param1 and
    	-- Param1 + Period, where:
    	-- - Param1 is the "first parameter", and
    	-- - Period the period of this BSpline curve.
    	--  Note: If this curve is not periodic, U is not modified.
                 
  SetPeriodic (me : mutable)
        --- Purpose :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 Knot(I2) - Knot(I1).
    	-- Consequently, the knots and poles tables are modified.
    	-- Exceptions
    	-- Standard_ConstructionError if this BSpline curve is not closed.
     raises ConstructionError;


  SetOrigin (me : mutable; Index : Integer)
    	---Purpose: 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.
    raises NoSuchObject,
    	   DomainError;
	

  SetNotPeriodic (me : mutable);
    	--- Purpose : Changes this BSpline curve into a non-periodic
    	-- curve. If this curve is already non-periodic, it is not modified.
    	-- Note that 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.
	        
 
  SetPole (me : mutable; Index : Integer; P : Pnt2d)
        --- Purpose : 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.
     raises OutOfRange;
      

  SetPole (me : mutable; Index : Integer; P : Pnt2d; Weight : Real)
    	--- Purpose : Modifies this BSpline curve by assigning P to the
    	-- pole of index Index in the poles table.
    	-- The second 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.
     raises OutOfRange,
                  ConstructionError;
	
  SetWeight (me : mutable; Index : Integer; Weight : Real)
        --- Purpose : Assigns the weight Weight to the pole of index Index of the poles table.
        --  If the curve was non rational it can become rational.
        --  If the curve was rational it can become non rational.
    	-- Exceptions
    	-- Standard_OutOfRange if Index is outside the
    	-- bounds of the poles table.
    	-- Standard_ConstructionError if Weight is negative or null.
    raises OutOfRange,
                  ConstructionError;

  MovePoint (me : mutable; U: Real; P: Pnt2d; Index1, Index2: Integer;
             FirstModifiedPole, LastModifiedPole: out Integer)
    	---Purpose : 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.
     raises OutOfRange;
       

    MovePointAndTangent (me : mutable; 
    	    	       U                 : Real; 
    	    	       P                 : Pnt2d; 
                       Tangent           : Vec2d ;
		       Tolerance         : Real ; 
    	    	       StartingCondition, 
                       EndingCondition   : Integer; 
    	    	       ErrorStatus       : out Integer) 

        ---Purpose : 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 enought degree of freedom
        -- with the constrain to deform the curve accordingly
        
     raises OutOfRange;
     
    
  IsCN (me; N : Integer)   returns Boolean
        --- Purpose : Returns true if the degree of continuity of this
    	-- BSpline curve is at least N. A BSpline curve is at least GeomAbs_C0.
    	-- Exceptions Standard_RangeError if N is negative.
          raises RangeError;
      
  IsG1 (me; theTf, theTl, theAngTol : Real) returns Boolean;
        ---Purpose :
		--  Check if curve has at least G1 continuity in interval [theTf, theTl]
        --  Returns true if IsCN(1)  
        --  or 
        --  angle betweem "left" and "right" first derivatives at
        --  knots with C0 continuity is less then theAngTol
		--  only knots in interval [theTf, theTl] is checked

  IsClosed (me)  returns Boolean;
        --- Purpose :
        --  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.


  IsPeriodic (me)  returns Boolean;
        --- Purpose : Returns True if the curve is periodic.


  IsRational (me)  returns Boolean;
        --- Purpose :
        --  Returns True if the weights are not identical.
        --  The tolerance criterion is Epsilon of the class Real.
    
  IsCacheValid(me;  Parameter : Real) returns Boolean
  
        ---Purpose :
        --           Tells whether the Cache is valid for the
        --           given parameter 
        -- Warnings : the parameter must be normalized within
        -- the period if the curve is periodic. Otherwise
        -- the answer will be false
        -- 
        is static private;
  
  Continuity (me)  returns Shape from GeomAbs;
        --- Purpose :
        --  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.


  Degree (me)  returns Integer;
        --- Purpose : Returns the degree of this BSpline curve.
        --  In this class the degree of the basis normalized B-spline
        --  functions cannot be greater than "MaxDegree"


        --- Purpose : Computation of value and derivatives

  D0 (me; U : Real; P : out Pnt2d);


  D1 (me; U : Real; P : out Pnt2d; V1 : out Vec2d)
     raises UndefinedDerivative;
        --- Purpose : Raised if the continuity of the curve is not C1.


  D2 (me; U : Real; P : out Pnt2d; V1, V2 : out Vec2d)
     raises UndefinedDerivative;
        --- Purpose : Raised if the continuity of the curve is not C2.


  D3 (me; U : Real; P : out Pnt2d; V1, V2, V3 : out Vec2d)
     raises UndefinedDerivative;
    	--- Purpose:  For this BSpline curve, computes
    	-- - the point P of parameter U, or
    	-- - the point P and one or more of the following values:
    	--   - V1, the first derivative vector,
    	--   - V2, the second derivative vector,
    	--   - V3, the third derivative vector.
    	-- Warning
    	-- On a point where the continuity of the curve is not the
    	-- one requested, these functions impact 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.
    	--   Raises UndefinedDerivative if the continuity of the curve is not C3.
    
  DN (me; U : Real; N : Integer)  returns Vec2d
        --- Purpose: 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.
    	--    Raises  UndefinedDerivative if the continuity of the curve is not CN.
        --   RangeError if N < 1.
     raises  UndefinedDerivative,
                  RangeError;

        --- Purpose: The following functions computes 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.


  LocalValue (me; U : Real; FromK1, ToK2 : Integer)   returns Pnt2d
     raises DomainError,
	--- Purpose : Raised if FromK1 = ToK2.
            OutOfRange;
	--- Purpose :
	--  Raised if FromK1 and ToK2 are not in the range 
	--  [FirstUKnotIndex, LastUKnotIndex].


  LocalD0 (me; U : Real; FromK1, ToK2 : Integer; 
           P : out Pnt2d)
     raises UndefinedDerivative, OutOfRange;
     
     
  LocalD1 (me; U : Real; FromK1, ToK2 : Integer; 
           P : out Pnt2d; V1 : out Vec2d)
     raises UndefinedDerivative,
        --- Purpose :
        --  Raised if the local continuity of the curve is not C1 
        --  between the knot K1 and the knot K2. 
            DomainError,
	--- Purpose : Raised if FromK1 = ToK2.
            OutOfRange;
	--- Purpose :
	--  Raised if FromK1 and ToK2 are not in the range 
	--  [FirstUKnotIndex, LastUKnotIndex].


  LocalD2 (me; U : Real; FromK1, ToK2 : Integer;
           P : out Pnt2d; V1, V2 : out Vec2d)
     raises UndefinedDerivative,
        --- Purpose :
        --  Raised if the local continuity of the curve is not C2 
        --  between the knot K1 and the knot K2. 
            DomainError,
	--- Purpose : Raised if FromK1 = ToK2.
            OutOfRange;
	--- Purpose :
	--  Raised if FromK1 and ToK2 are not in the range 
	--  [FirstUKnotIndex, LastUKnotIndex].


  LocalD3 (me; U : Real;  FromK1, ToK2 : Integer;
           P : out Pnt2d; V1, V2, V3 : out Vec2d)
     raises UndefinedDerivative,
        --- Purpose :
        --  Raised if the local continuity of the curve is not C3
        --  between the knot K1 and the knot K2. 
            DomainError,
	--- Purpose : Raised if FromK1 = ToK2.
            OutOfRange;
	--- Purpose :
	--  Raised if FromK1 and ToK2 are not in the range
	--  [FirstUKnotIndex, LastUKnotIndex].


  LocalDN (me; U : Real;  FromK1, ToK2 : Integer; N : Integer)  returns Vec2d
     raises  UndefinedDerivative,
        --- Purpose :
        --  Raised if the local continuity of the curve is not CN
        --  between the knot K1 and the knot K2. 
            DomainError,
	--- Purpose : Raised if FromK1 = ToK2.
             RangeError,
        --- Purpose : Raised if N < 1.
             OutOfRange;
	--- Purpose :
	--  Raises if FromK1 and ToK2 are not in the range 
	--  [FirstUKnotIndex, LastUKnotIndex].


  EndPoint (me)   returns Pnt2d;
        --- Purpose :
        --  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.


  FirstUKnotIndex (me)   returns Integer;
        --- Purpose :
        --  For a B-spline curve the first parameter (which gives the start
        --  point of the curve) is a knot value but if the multiplicity of
        --  the first knot index is lower than Degree + 1 it is not the 
        --  first knot of the curve. This method computes the index of the
        --  knot corresponding to the first parameter.


  FirstParameter (me)   returns Real;
        --- Purpose :
        --  Computes the parametric value of the start point of the curve.
        --  It is a knot value.


  Knot (me; Index : Integer)   returns Real
        --- Purpose :
        --  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.
     raises OutOfRange;
        --- Purpose : Raised if Index < 1 or Index > NbKnots


  Knots (me; K : out Array1OfReal from TColStd)
        --- Purpose : returns the knot values of the B-spline curve;
     raises DimensionError;
        --- Purpose :
        --  Raised if the length of K is not equal to the number of knots.


  KnotSequence (me; K : out Array1OfReal from TColStd)
        --- Purpose : Returns the knots sequence.
        --  In this sequence the knots with a multiplicity greater than 1
        --  are repeated. 
        -- Example :
        --  K = {k1, k1, k1, k2, k3, k3, k4, k4, k4}
     raises DimensionError;
        --- Purpose :
        --  Raised if the length of K is not equal to NbPoles + Degree + 1


  KnotDistribution (me) returns BSplKnotDistribution from GeomAbs;
        --- Purpose :
        --  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.


  LastUKnotIndex (me)  returns Integer;
        --- Purpose :
        --  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.


  LastParameter (me)   returns Real;
        --- Purpose :
        --  Computes the parametric value of the end point of the curve.
        --  It is a knot value.


  LocateU (me;
           U                   : Real; 
           ParametricTolerance : Real; 
           I1, I2              : in out Integer;
           WithKnotRepetition  : Boolean = Standard_False);
        --- Purpose :
        --  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) - Abs(ParametricTolerance)
        --  . if I2 > NbKnots => U > Knots (NbKnots) + Abs(ParametricTolerance)


  Multiplicity (me; Index : Integer)   returns Integer
        --- Purpose :
        --  Returns the multiplicity of the knots of range Index.
     raises OutOfRange;
        --- Purpose : Raised if Index < 1 or Index > NbKnots


  Multiplicities (me; M : out Array1OfInteger from TColStd)
        --- Purpose :
        --  Returns the multiplicity of the knots of the curve.
     raises DimensionError;
        --- Purpose :
        --  Raised if the length of M is not equal to NbKnots.


  NbKnots (me)  returns Integer;
        --- Purpose :
        --  Returns the number of knots. This method returns the number of 
        --  knot without repetition of multiple knots.


  NbPoles (me)  returns Integer;
        --- Purpose : Returns the number of poles


  Pole (me; Index : Integer)   returns Pnt2d
        --- Purpose : Returns the pole of range Index.
     raises OutOfRange;
        --- Purpose : Raised if Index < 1 or Index > NbPoles.


  Poles (me; P : out Array1OfPnt2d)
        --- Purpose : Returns the poles of the B-spline curve;
     raises DimensionError;
        --- Purpose : 
        --  Raised if the length of P is not equal to the number of poles.


  StartPoint (me)  returns Pnt2d;
        --- Purpose :
        --  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.


  Weight (me; Index : Integer)  returns Real  
        --- Purpose : Returns the weight of the pole of range Index .
     raises OutOfRange;
        --- Purpose : Raised if Index < 1 or Index > NbPoles.


  Weights (me; W : out Array1OfReal from TColStd)
        --- Purpose : Returns the weights of the B-spline curve;
     raises DimensionError;
        --- Purpose :
        --  Raised if the length of W is not equal to NbPoles.


  Transform (me : mutable; T : Trsf2d);
---Purpose: Applies the transformation T to this BSpline curve.

  MaxDegree (myclass)  returns Integer;
        --- Purpose :
        --  Returns the value of the maximum degree of the normalized 
        --  B-spline basis functions in this package.


  Resolution(me          : mutable; 
    	     ToleranceUV : Real;
             UTolerance  : out Real); 
	---Purpose:  Computes for this BSpline curve the parametric
    	-- tolerance UTolerance for a given tolerance
    	-- Tolerance3D (relative to dimensions in the plane).
    	-- If f(t) is the equation of this BSpline curve,
    	-- UTolerance ensures that:
	--           | t1 - t0| < Utolerance ===> 
	--           |f(t1) - f(t0)| < ToleranceUV


  Copy (me)  returns like me;
    	---Purpose: Creates a new object which is a copy of this BSpline curve.  
    
  UpdateKnots(me : mutable)
    	---Purpose: Recompute  the  flatknots,  the knotsdistribution, the continuity.
  is static private;
  
  InvalidateCache(me : mutable)
	---Purpose : Invalidates the cache. This has to be private this has to be private
      is static private;

  
  ValidateCache(me : mutable ; Parameter : Real) 
  
    is static private;
    	---Purpose : updates the cache and validates it
             
fields

  rational  : Boolean;
  periodic  : Boolean;
  knotSet   : BSplKnotDistribution from GeomAbs; 
  smooth    : Shape from GeomAbs;
  deg       : Integer;
  poles     : HArray1OfPnt2d from TColgp;
  weights   : HArray1OfReal from TColStd;
  flatknots : HArray1OfReal from TColStd;
  knots     : HArray1OfReal from TColStd;
  mults     : HArray1OfInteger from TColStd;
  cachepoles      : HArray1OfPnt2d     from TColgp;
  -- Taylor expansion of the poles function, in homogeneous
  -- form if the curve is rational. The taylor expansion
  -- is normalized so that the span corresponds to
  -- [0 1] see below
  cacheweights    : HArray1OfReal    from TColStd;
  -- Taylor expansion of the poles function, in homogeneous
  -- form if the curve is rational. The taylor expansion
  -- is normalized so that the span corresponds to
  -- [0 1] see below
  validcache      : Integer;
  -- = 1 the cache is valid 
  -- = 0 the cache is invalid
  parametercache    : Real;
  -- Parameter at which the Taylor expension is stored in 
  -- the cache
  spanlenghtcache   : Real;
  -- Since the Taylor expansion is normalized in the 
  -- cache to evaluate the cache one has to use
  -- (Parameter - refcache) * normcache 
  spanindexcache : Integer;
  -- the span for which the cache is valid if 
  -- validcache is 1 

  -- usefull to evaluate the parametric resolution
  maxderivinv   : Real from Standard;
  maxderivinvok : Boolean from Standard;

  myMutex       : Mutex from Standard;
  -- protected bspline-cache

end;