-- Created on: 1992-01-30
-- Created by: Didier PIFFAULT
-- Copyright (c) 1992-1999 Matra Datavision
-- Copyright (c) 1999-2012 OPEN CASCADE SAS
--
-- The content of this file is subject to the Open CASCADE Technology Public
-- License Version 6.5 (the "License"). You may not use the content of this file
-- except in compliance with the License. Please obtain a copy of the License
-- at http://www.opencascade.org and read it completely before using this file.
--
-- The Initial Developer of the Original Code is Open CASCADE S.A.S., having its
-- main offices at: 1, place des Freres Montgolfier, 78280 Guyancourt, France.
--
-- The Original Code and all software distributed under the License is
-- distributed on an "AS IS" basis, without warranty of any kind, and the
-- Initial Developer hereby disclaims all such warranties, including without
-- limitation, any warranties of merchantability, fitness for a particular
-- purpose or non-infringement. Please see the License for the specific terms
-- and conditions governing the rights and limitations under the License.



class CurveTransition from TopTrans 

	---Purpose: This algorithm  is used to  compute the transition
	--          of a Curve intersecting a curvilinear boundary.
	--          
	--          The geometric  elements  are described locally  at
	--          the   intersection   point  by    a   second order
	--          development.
	--          
	--          The curve is described  by the intersection point,
	--          the tangent vector and the curvature.
	--          
	--          The  boundary  is described  by   a set  of  curve
	--          elements, a curve element is either :
	--          
	--          - A curve.
	--          
	--          - A curve and an orientation  called a half-curve,
	--          the boundary  of the curve is  before or after the
	--          intersection point depending on the orientation.
	--          

uses

    Boolean from Standard,
    Real from Standard,
    
    Pnt from gp,
    Dir from gp,
    
    State from TopAbs,
    Orientation from TopAbs

is

    Create returns CurveTransition from TopTrans;
	---Purpose: Create an empty  Curve Transition.


    Reset( me   : in out;
    	   Tgt  : in Dir from gp;        -- Tangent at this point      
    	   Norm : in Dir from gp;        -- Normal vector at this point
    	   Curv : in Real from Standard);-- Curvature at this point     
	---Purpose: Initialize a Transition with the local description
	--          of a Curve.
    
    Reset( me   : in out;
    	   Tgt  : in Dir from gp);       -- Tangent at this point      
	---Purpose: Initialize a Transition with the local description
	--          of a straigth line.
    
    Compare(me : in out;
    	    Tole : in Real from Standard;    -- Cosine tolerance
    	    Tang : in Dir from gp;           -- Tangent on curve for this point
   	    Norm : in Dir from gp;           -- Normal vector at this point
    	    Curv : in Real from Standard;    -- Curvature at this point    
    	    S  : in Orientation from TopAbs; -- transition locale    
    	    Or : in Orientation from TopAbs);-- orientation de la tangente
	---Purpose: Add  a curve element to the  boundary.    If Or is
	--          REVERSED  the curve  is   before the intersection,
	--          else if  Or  is FORWARD  the   curv  is after  the
	--          intersection   and    if   Or  is   INTERNAL   the
	--          intersection is in the middle of the curv.

    StateBefore(me) returns State from TopAbs;
	---Purpose: returns   the  state   of  the   curve  before the
	--          intersection, this is the position relative to the
	--          boundary of a point very close to the intersection
	--          on the negative side of the tangent.
	
    StateAfter(me) returns State from TopAbs;
	---Purpose: returns  the    state of  the  curve   after   the
	--          intersection, this is the position relative to the
	--          boundary of a point very close to the intersection
	--          on the positive side of the tangent.


---Implementation functions :

    IsBefore(   me;
    	    	Tole : in Real from Standard;
    	    	Angl : in Real from Standard;
    	    	Nor1 : in Dir from gp;
    	    	Cur1 : in Real from Standard;
    	    	Nor2 : in Dir from gp;
    	    	Cur2 : in Real from Standard) 
    	    	returns Boolean from Standard is private;
    	---Purpose: Compare two curvature and return true  if N1,C1 is
    	--          before N2,C2 in the edge orientation

    Compare(me;
    	    Ang1 : in Real from Standard;
    	    Ang2 : in Real from Standard;
    	    Tole : in Real from Standard)
    	    returns Integer from Standard is private;
    	---Purpose: Compare two angles at tolerance Tole
	    
	    
fields

    myTgt  : Dir from gp;     -- Tangent at this point      
    myNorm : Dir from gp;     -- Normal vector at this point
    myCurv : Real;            -- Curvature at this point    
    
    Init   : Boolean;

    TgtFirst  : Dir from gp;  -- Elements to determine the state
    NormFirst : Dir from gp;  -- 
    CurvFirst : Real;         -- before the intersection
    TranFirst : Orientation from TopAbs;

    TgtLast  : Dir from gp;   -- Elements to determine the state
    NormLast : Dir from gp;   -- 
    CurvLast : Real;          -- After the intersection
    TranLast : Orientation from TopAbs;

end CurveTransition;