path: root/src/Geom2d/Geom2d_Curve.cdl

-- File:	Geom2d_Curve.cdl
-- Created:	Wed Mar 24 18:00:39 1993
-- Author:	JCV
--		<fid@sdsun2>
-- Copyright:	 Matra Datavision 1993

---Copyright:   Matra Datavision 1991, 1992

deferred class Curve from Geom2d inherits Geometry from Geom2d

    	--- Purpose : 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:
    	-- - 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
    	-- explicitly states so.
    	-- Warning
    	-- The Geom2d package does not prevent the
    	-- construction of curves with null length or curves which
    	-- self-intersect.
  


uses Pnt2d   from gp,
     Vec2d   from gp,
     Trsf2d  from gp,
     Shape  from GeomAbs
     
     
raises RangeError          from Standard,
       NoSuchObject        from Standard,
       UndefinedDerivative from Geom2d,
       UndefinedValue      from Geom2d


is



  Reverse (me : mutable) 
        --- Purpose :
        --  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.
     is deferred;  


  ReversedParameter(me; U : Real) returns Real
	---Purpose: 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.
     is deferred;  


  TransformedParameter(me; U : Real; T : Trsf2d from gp) returns Real
	---Purpose: 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).
     is virtual;  

  ParametricTransformation(me; T : Trsf2d from gp) returns Real
	---Purpose: 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).
     is virtual;  

  Reversed (me)  returns mutable like me 
        --- Purpose : 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:
    	-- - 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.
     is static;



  FirstParameter (me)   returns Real
        --- Purpose : Returns the value of the first parameter.
        --  Warnings :
        --  It can be RealFirst or RealLast from package Standard 
        --  if the curve is infinite
     is deferred;


  LastParameter (me)   returns Real
        --- Purpose : Value of the last parameter.
        --  Warnings :
        --  It can be RealFirst or RealLast from package Standard 
        --  if the curve is infinite
     is deferred;


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


  IsPeriodic (me)  returns Boolean
        --- Purpose :
    	-- 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.
     is deferred;


  Period (me) returns Real from Standard
    	---Purpose: Returns thne period of this curve.
  raises
    	NoSuchObject from Standard
	---Purpose: raises if the curve is not periodic
  is virtual;

  Continuity (me)   returns Shape from GeomAbs
        --- Purpose :
        --  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.
     is deferred;


  IsCN (me; N : Integer)  returns Boolean
        --- Purpose : Returns true if the degree of continuity of this curve is at least N.
    	-- Exceptions Standard_RangeError if N is less than 0.
     raises RangeError
     is deferred;


  D0(me; U : Real; P : out Pnt2d)
	---Purpose: 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.
     raises  UndefinedValue
        ---Purpose :
        --  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.
     is deferred;


  D1 (me; U : Real; P : out Pnt2d; V1 : out Vec2d)
        --- Purpose :
        --  Returns the point P of parameter U and the first derivative V1.
     raises UndefinedDerivative
        --- Purpose : Raised if the continuity of the curve is not C1.
     is deferred;


  D2 (me; U : Real; P : out Pnt2d; V1, V2 : out Vec2d)
        --- Purpose :
        --  Returns the point P of parameter U, the first and second
        --  derivatives V1 and V2.
     raises UndefinedDerivative
        --- Purpose : Raised if the continuity of the curve is not C2.
     is deferred;


  D3 (me; U : Real; P : out Pnt2d; V1, V2, V3 : out Vec2d)
        --- Purpose :
        --  Returns the point P of parameter U, the first, the second 
        --  and the third derivative.
     raises UndefinedDerivative
        --- Purpose : Raised if the continuity of the curve is not C3.
     is deferred;
        

  DN (me; U : Real; N : Integer)   returns Vec2d
        --- Purpose : For the point of parameter U of this curve, computes
    	-- the vector corresponding to the Nth derivative.
    	-- Exceptions
    	-- StdFail_UndefinedDerivative if:
    	-- - 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.
          raises  UndefinedDerivative,
                  RangeError
     is deferred;


  Value (me; U : Real)    returns Pnt2d
        --- Purpose : 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.
     raises  UndefinedValue
        --- Purpose :
        --  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.
     is static;


end;