-- File:	BRepAlgo_Section.cdl
-- Created:	Fri Feb 18 09:48:50 1994
-- Author:	Remi LEQUETTE
--		<rle@nonox>
---Copyright:	 Matra Datavision 1994

class Section from BRepAlgo inherits BooleanOperation from BRepAlgo

    	---Purpose: Construction of the section lines between two shapes.
    	-- For this Boolean operation, each face of the first
    	-- shape is intersected by each face of the second
    	-- shape. The resulting intersection edges are brought
    	-- together into a compound object, but not chained or
    	-- grouped into wires.
    	-- Computation of the intersection of two Shapes or Surfaces
    	-- The two parts involved in this Boolean operation may
    	-- be defined from geometric surfaces: the most common
    	-- use is the computation of the planar section of a shape.
    	-- A Section object provides the framework for:
    	-- - defining the shapes to be intersected, and the
    	--   computation options,
    	-- - implementing the construction algorithm, and
    	-- - consulting the result.
    	-- Example : giving two shapes S1,S2 accessing faces,
    	-- let compute the section edges R on S1,S2, 
    	-- performing approximation on new curves,
    	-- performing PCurve on part 1 but not on part 2 :
    	-- Standard_Boolean PerformNow = Standard_False;
    	-- BRepBoolAPI_Section S(S1,S2,PerformNow);
    	-- S.ComputePCurveOn1(Standard_True);
    	-- S.Approximation(Standard_True);
    	-- S.Build();
    	-- TopoDS_Shape R = S.Shape();
    	-- On Null Shapes of geometries, NotDone() is called. 

uses

 Shape from TopoDS,
 Surface from Geom,
 Pln from gp,
 Curve from Geom2d
 
is

 Create(Sh1,Sh2 : Shape from TopoDS;
    	PerformNow : Boolean = Standard_True)
 returns Section from BRepAlgo;
	
 Create(Sh : Shape from TopoDS; Pl : Pln from gp;
    	PerformNow : Boolean = Standard_True)
    	
 returns Section from BRepAlgo;

 Create(Sh : Shape from TopoDS; Sf : Surface from Geom;
 	PerformNow : Boolean = Standard_True)

 returns Section from BRepAlgo;

 Create(Sf : Surface from Geom; Sh : Shape from TopoDS;
 	 PerformNow : Boolean = Standard_True)
 
 returns Section from BRepAlgo;

 Create(Sf1 : Surface from Geom; Sf2 : Surface from Geom;
    	PerformNow : Boolean = Standard_True)
    	---Purpose: This and the above algorithms construct a framework for computing the section lines of
    	-- - the two shapes Sh1 and Sh2, or
    	-- - the shape Sh and the plane Pl, or
    	-- - the shape Sh and the surface Sf, or
    	-- - the surface Sf and the shape Sh, or
    	-- - the two surfaces Sf1 and Sf2,
    	--   and builds the result if PerformNow equals true, its
    	-- default value. If PerformNow equals false, the
    	-- intersection will be computed later by the function Build.
    	-- The constructed shape will be returned by the
    	-- function Shape. This is a compound object
    	-- composed of edges. These intersection edges may be built:
    	-- - on new intersection lines, or
    	-- - on coincident portions of edges in the two intersected shapes.
    	--   These intersection edges are independent: they
    	-- are not chained or grouped in wires.
    	-- If no intersection edge exists, the result is an empty compound object.
    	-- Note that other objects than TopoDS_Shape
    	-- shapes involved in these syntaxes are converted
    	-- into faces or shells before performing the
    	-- computation of the intersection. A shape resulting
    	-- from this conversion can be retrieved with the
    	-- function Shape1 or Shape2.
    	-- Parametric 2D curves on intersection edges
    	-- No parametric 2D curve (pcurve) is defined for
    	-- each elementary edge of the result. To attach such
    	-- parametric curves to the constructed edges you
    	-- may use a constructor with the PerformNow flag
    	-- equal to false; then you use:
    	-- - the function ComputePCurveOn1 to ask for the
    	--   additional computation of a pcurve in the
    	--   parametric space of the first shape,
    	-- - the function ComputePCurveOn2 to ask for the
    	--   additional computation of a pcurve in the
    	--   parametric space of the second shape,
    	-- - in the end, the function Build to construct the result.
    	--   Note that as a result, pcurves will only be added on
    	-- edges built on new intersection lines.
    	-- Approximation of intersection edges
    	-- The underlying 3D geometry attached to each
    	-- elementary edge of the result is:
    	-- - analytic where possible, provided the
    	--   corresponding geometry corresponds to a type
    	--   of analytic curve defined in the Geom package;
    	--   for example, the intersection of a cylindrical
    	--   shape with a plane gives an ellipse or a circle;
    	-- - or elsewhere, given as a succession of points
    	--   grouped together in a BSpline curve of degree 1.
    	--   If you prefer to have an attached 3D geometry
    	-- which is a BSpline approximation of the computed
    	-- set of points on computed elementary intersection
    	-- edges whose underlying geometry is not analytic,
    	-- you may use a constructor with the PerformNow
    	-- flag equal to false. Then you use:
    	-- - the function Approximation to ask for this
    	--   computation option, and
    	-- - the function Build to construct the result.
    	--   Note that as a result, approximations will only be
    	-- computed on edges built on new intersection lines.
    	-- Example
    	--   You may also combine these computation options.
    	-- In the following example:
    	-- - each elementary edge of the computed
    	--   intersection, built on a new intersection line,
    	--   which does not correspond to an analytic Geom
    	--   curve, will be approximated by a BSpline curve
    	--   whose degree is not greater than 8.
    	-- - each elementary edge built on a new intersection line, will have:
    	--   - a pcurve in the parametric space of the shape S1,
    	--   - no pcurve in the parametric space of the shape S2.
    	--     // TopoDS_Shape S1 = ... , S2 = ... ;
    	-- Standard_Boolean PerformNow = Standard_False;
    	-- BRepAlgo_Section S ( S1, S2, PerformNow );
    	-- S.ComputePCurveOn1 (Standard_True);
    	-- S.Approximation (Standard_True);
    	-- S.Build();
    	-- TopoDS_Shape R = S.Shape();
    
 returns Section from BRepAlgo;

 Init1(me : out;S1 : Shape from TopoDS);
    	---Purpose: Initializes the first part
 
 Init1(me : out;Pl : Pln from gp);
    	---Purpose: Initializes the first part
 
 Init1(me : out;Sf : Surface from Geom);
    	---Purpose: Initializes the first part
 
 Init2(me : out;S2 : Shape from TopoDS);
    	---Purpose: initialize second part
 
 Init2(me : out;Pl : Pln from gp);
    	---Purpose: Initializes the second part
 
 Init2(me : out;Sf : Surface from Geom);
    	---Purpose: This and the above algorithms 
    	--   reinitialize the first and the second parts on which
    	-- this algorithm is going to perform the intersection
    	-- computation. This is done with either: the surface
    	-- Sf, the plane Pl or the shape Sh.
    	-- You use the function Build to construct the result.
 
 Approximation(me : out;B : Boolean);
    	---Purpose: Defines an option for computation of further
    	--- intersections. This computation will be performed by
    	-- the function Build in this framework.
    	-- By default, the underlying 3D geometry attached to
    	-- each elementary edge of the result of a computed intersection is:
    	-- - analytic where possible, provided the
    	--   corresponding geometry corresponds to a type of
    	--   analytic curve defined in the Geom package; for
    	--   example the intersection of a cylindrical shape with
    	--   a plane gives an ellipse or a circle;
    	-- - or elsewhere, given as a succession of points
    	--   grouped together in a BSpline curve of degree 1. If
    	--   Approx equals true, when further computations are
    	--   performed in this framework with the function
    	--   Build, these edges will have an attached 3D
    	--   geometry which is a BSpline approximation of the
    	--  computed set of points.
    	--   Note that as a result, approximations will be computed
    	-- on edges built only on new intersection lines.
 
 ComputePCurveOn1(me : out;B : Boolean);
    	---Level: Public
    	---Purpose: Indicates if the Pcurve must be (or not) performed on first part. 

 ComputePCurveOn2(me : out;B : Boolean);
    	---Level: Public
    	---Purpose: Define options for the computation of further
    	-- intersections which will be performed by the function
    	-- Build in this framework.
    	-- By default, no parametric 2D curve (pcurve) is defined
    	-- for the elementary edges of the result.
    	-- If ComputePCurve1 equals true, further computations
    	-- performed in this framework with the function Build
    	-- will attach an additional pcurve in the parametric
    	-- space of the first shape to the constructed edges.
    	-- If ComputePCurve2 equals true, the additional pcurve
    	-- will be attached to the constructed edges in the
    	-- parametric space of the second shape.
    	-- These two functions may be used together.
    	-- Note that as a result, pcurves will only be added onto
    	-- edges built on new intersection lines.
 
 Build(me : in out)
    	---Purpose:  Performs the computation of the section lines
    	-- between the two parts defined at the time of
    	-- construction of this framework or reinitialized with the
    	-- Init1 and Init2 functions.
    	-- The constructed shape will be returned by the function
    	-- Shape. This is a compound object composed of
    	-- edges. These intersection edges may be built:
    	-- - on new intersection lines, or
    	-- - on coincident portions of edges in the two intersected shapes.
    	--   These intersection edges are independent: they are
    	-- not chained or grouped into wires.
    	-- If no intersection edge exists, the result is an empty compound object.
    	-- The shapes involved in the construction of the section
    	-- lines can be retrieved with the function Shape1 or
    	-- Shape2. Note that other objects than
    	-- TopoDS_Shape shapes given as arguments at the
    	-- construction time of this framework, or to the Init1 or
    	--   Init2 function, are converted into faces or shells
    	-- before performing the computation of the intersection.
    	-- Parametric 2D curves on intersection edges
    	-- No parametric 2D curve (pcurve) is defined for the
    	-- elementary edges of the result. To attach parametric
    	-- curves like this to the constructed edges you have to use:
    	-- - the function ComputePCurveOn1 to ask for the
    	--   additional computation of a pcurve in the
    	--   parametric space of the first shape,
    	-- - the function ComputePCurveOn2 to ask for the
    	--   additional computation of a pcurve in the
    	--   parametric space of the second shape.
    	-- This must be done before calling this function.
    	-- Note that as a result, pcurves are added on edges
    	-- built on new intersection lines only.
    	-- Approximation of intersection edges
    	-- The underlying 3D geometry attached to each
    	-- elementary edge of the result is:
    	-- - analytic where possible provided the corresponding
    	--   geometry corresponds to a type of analytic curve
    	--   defined in the Geom package; for example, the
    	--   intersection of a cylindrical shape with a plane
    	--   gives an ellipse or a circle; or
    	-- - elsewhere, given as a succession of points grouped
    	--   together in a BSpline curve of degree 1.
    	--   If, on computed elementary intersection edges whose
    	-- underlying geometry is not analytic, you prefer to
    	-- have an attached 3D geometry which is a BSpline
    	-- approximation of the computed set of points, you have
    	-- to use the function Approximation to ask for this
    	-- computation option before calling this function.
    	-- You may also have combined these computation
    	-- options: look at the example given above to illustrate
    	-- the use of the constructors.
 is redefined static;

 HasAncestorFaceOn1(me; E : Shape from TopoDS;
 	    	    	F : out Shape from TopoDS)
 returns Boolean;
    	---Purpose:Identifies the ancestor faces of the new
    	-- intersection edge E resulting from the last
    	-- computation performed in this framework, that is,
    	-- the faces of the two original shapes on which the edge E lies:
    	-- - HasAncestorFaceOn1 gives the ancestor face
    	--   in the first shape, and
    	--   These functions return:
    	-- - true if an ancestor face F is found, or
    	-- - false if not.
    	--   An ancestor face is identifiable for the edge E if the
    	-- three following conditions are satisfied:
    	-- - the first part on which this algorithm performed
    	--   its last computation is a shape, that is, it was not
    	--   given as a surface or a plane at the time of
    	--   construction of this algorithm or at a later time by
    	--   the Init1 function,
    	-- - E is one of the elementary edges built by the last
    	--   computation of this section algorithm,
    	-- - the edge E is built on an intersection curve. In
    	--   other words, E is a new edge built on the
    	--   intersection curve, not on edges belonging to the
    	--   intersecting shapes.
    	--   To use these functions properly, you have to test
    	-- the returned Boolean value before using the
    	-- ancestor face: F is significant only if the returned
    	-- Boolean value equals true.

 HasAncestorFaceOn2(me; E : Shape from TopoDS;
 	    	    	F : out Shape from TopoDS)
 returns Boolean;
    	---Purpose: Identifies the ancestor faces of the new
    	-- intersection edge E resulting from the last
    	-- computation performed in this framework, that is,
    	-- the faces of the two original shapes on which the edge E lies:
    	-- - HasAncestorFaceOn2 gives the ancestor face in the second shape.
    	--   These functions return:
    	-- - true if an ancestor face F is found, or
    	-- - false if not.
    	--   An ancestor face is identifiable for the edge E if the
    	-- three following conditions are satisfied:
    	-- - the first part on which this algorithm performed
    	--   its last computation is a shape, that is, it was not
    	--   given as a surface or a plane at the time of
    	--   construction of this algorithm or at a later time by
    	--   the Init1 function,
    	-- - E is one of the elementary edges built by the last
    	--   computation of this section algorithm,
    	-- - the edge E is built on an intersection curve. In
    	--   other words, E is a new edge built on the
    	--   intersection curve, not on edges belonging to the
    	--   intersecting shapes.
    	--   To use these functions properly, you have to test
    	-- the returned Boolean value before using the
    	-- ancestor face: F is significant only if the returned
    	-- Boolean value equals true.

 PCurveOn1(me; E : Shape from TopoDS)
 returns Curve from Geom2d;
    	---Purpose: Returns the pcurve attached to section edge E, in the
    	-- parametric space of  the first part
    	-- on which this algorithm has previously performed the
    	-- computation of a section.
    	-- Warning
    	-- - No pcurve is attached to an elementary edge of the
    	--   resulting section, and the function returns a null
    	--   handle, unless the function ComputePCurveOn1
    	--   or ComputePCurveOn2 was previously used to
    	--   define this sort of option of computation.
    	-- - A null handle is also returned if the edge E does
    	--   not belong to the last computed intersection, that is,
    	--   if it is not one of the elementary edges of the
    	--   compound object returned by the function Shape.


 PCurveOn2(me; E : Shape from TopoDS)
 returns Curve from Geom2d;
    	---Purpose: Returns the pcurve attached to section edge E, in the
    	-- parametric space of  the second part
    	-- on which this algorithm has previously performed the
    	-- computation of a section.
    	-- Warning
    	-- - No pcurve is attached to an elementary edge of the
    	--   resulting section, and the function returns a null
    	--   handle, unless the function ComputePCurveOn1
    	--   or ComputePCurveOn2 was previously used to
    	--   define this sort of option of computation.
    	-- - A null handle is also returned if the edge E does
    	--   not belong to the last computed intersection, that is,
    	--   if it is not one of the elementary edges of the
    	--   compound object returned by the function Shape.

 InitParameters(me : out)
 ---Level: Public
 ---Level: Private
 is redefined private;
 
fields

 myS1Changed : Boolean;
 myS2Changed : Boolean;
 myApproxChanged : Boolean;
 myPCurve1Changed : Boolean;
 myPCurve2Changed : Boolean;
 myshapeisnull : Boolean;

end Section;