--
-- File      : ConicArc.cdl
-- Created   : Sat 9 Jan 1993
-- Author    : CKY / Contract Toubro-Larsen (Kiran)
--
---Copyright : MATRA-DATAVISION  1993
--

class ConicArc from IGESGeom  inherits IGESEntity

        ---Purpose: defines IGESConicArc, Type <104> Form <0-3>  in package IGESGeom
        --          A conic arc is a bounded connected portion of a parent
        --          conic curve which consists of more than one point. The
        --          parent conic curve is either an ellipse, a parabola, or
        --          a hyperbola. The definition space coordinate system is
        --          always chosen so that the conic arc lies in a plane either
        --          coincident with or parallel to XT, YT plane. Within such
        --          a plane a conic is defined by the six coefficients in the
        --          following equation.
        --          A*XT^2 + B*XT*YT + C*YT^2 + D*XT + E*YT + F = 0

uses

        Pnt         from gp,
        Pnt2d       from gp,
        Dir         from gp,
        XY          from gp

is

        Create returns mutable ConicArc;

        -- Specific Methods pertaining to the class

        Init (me                   : mutable;
              A, B, C, D, E, F, ZT : Real;
              aStart, anEnd        : XY);
        ---Purpose : This method is used to set the fields of the class
        --           ConicalArc
        --       - A, B, C, D, E, F : Coefficients of the equation
        --                            defining conic arc
        --       - ZT               : Parallel ZT displacement of the arc
        --                            from XT, YT plane.
        --       - aStart           : Starting point of the conic arc
        --       - anEnd            : End point of the conic arc

    	OwnCorrect (me : mutable) returns Boolean;
	---Purpose : sets the Form Number equal to ComputedFormNumber,
	--           returns True if changed

    	ComputedFormNumber (me) returns Integer;
	---Purpose : Computes the Form Number according to the equation
	--           1 for Ellipse, 2 for Hyperbola, 3 for Parabola

        Equation (me; A, B, C, D, E, F : out Real);
        -- returns the basic equation defining the arc
        -- A, B, C, D, E, F are the coefficients of the equation

        ZPlane (me) returns Real;
        ---Purpose : returns the Z displacement of the arc from XT, YT plane

        StartPoint (me) returns Pnt2d;
        ---Purpose : returns the starting point of the arc

        TransformedStartPoint (me) returns Pnt;
        ---Purpose : returns the starting point of the arc after applying
        -- Transf. Matrix

        EndPoint (me) returns Pnt2d;
        ---Purpose : returns the end point of the arc

        TransformedEndPoint (me) returns Pnt;
        ---Purpose : returns the end point of the arc after applying
        -- Transf. Matrix

        IsFromEllipse (me) returns Boolean;
        ---Purpose : returns True if parent conic curve is an ellipse

        IsFromParabola (me) returns Boolean;
        ---Purpose : returns True if parent conic curve is a parabola

        IsFromHyperbola (me) returns Boolean;
        ---Purpose : returns True if parent conic curve is a hyperbola

        IsClosed (me) returns Boolean;
        ---Purpose : returns True if StartPoint = EndPoint


        Axis(me) returns Dir;
        ---Purpose : Z-Axis of conic (i.e. [0,0,1])

    	TransformedAxis (me) returns Dir;
	---Purpose : Z-Axis after applying Trans. Matrix

    	Definition (me; Center : out Pnt; MainAxis : out Dir;
    	    	        rmin, rmax : out Real);
    	---Purpose : Returns a Definition computed from equation, easier to use
    	--           <Center> : the center of the the conic (meaningless for
    	--                      a parabola) (defined with Z displacement)
    	--           <MainAxis> : the Main Axis of the conic (for a Circle,
    	--                        arbitrary the X Axis)
    	--           <Rmin,Rmax> : Minor and Major Radii of the conic
    	--                         For a Circle, Rmin = Rmax,
    	--                         For a Parabola, Rmin = Rmax = the Focal
    	--  Warning : the basic definition (by equation) is not very stable,
    	--           limit cases may be approximative

    	TransformedDefinition (me; Center : out Pnt; MainAxis : out Dir;
    	    	            	   rmin, rmax : out Real);
    	---Purpose : Same as Definition, but the Location is applied on the
    	--           Center and the MainAxis

    	ComputedDefinition (me; Xcen,Ycen, Xax, Yax, Rmin,Rmax : out Real);
	---Purpose : Computes and returns the coordinates of the definition of
	--           a comic from its equation. Used by Definition &
	--           TransformedDefinition, or may be called directly if needed

fields

--
-- Class    : IGESGeom_ConicArc
--
-- Purpose  : Declaration of variables specific to the definition
--            of the Class ConicArc.
--
-- Reminder : A ConicArc instance is defined by :
--            The six coefficients in the following equation.
--            A*XT^2 + B*XT*YT + C*YT^2 + D*XT + E*YT + F = 0
--            The parent curve could be a parabola or a hyperbola
--            or an ellipse. The arc has one start and one end point.

            theA     : Real;
            theB     : Real;
            theC     : Real;
            theD     : Real;
            theE     : Real;
            theF     : Real;
                --  Conic coefficients

            theZT    : Real;
            theStart : XY;
            theEnd   : XY;

end ConicArc;