BRepAlgo_Section Class Reference

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:
More...

#include <BRepAlgo_Section.hxx>

Inheritance diagram for BRepAlgo_Section:

Public Member Functions
	BRepAlgo_Section (const TopoDS_Shape &Sh1, const TopoDS_Shape &Sh2, const Standard_Boolean PerformNow=Standard_True)
	BRepAlgo_Section (const TopoDS_Shape &Sh, const gp_Pln &Pl, const Standard_Boolean PerformNow=Standard_True)
	BRepAlgo_Section (const TopoDS_Shape &Sh, const Handle< Geom_Surface > &Sf, const Standard_Boolean PerformNow=Standard_True)
	BRepAlgo_Section (const Handle< Geom_Surface > &Sf, const TopoDS_Shape &Sh, const Standard_Boolean PerformNow=Standard_True)
	BRepAlgo_Section (const Handle< Geom_Surface > &Sf1, const Handle< Geom_Surface > &Sf2, const Standard_Boolean PerformNow=Standard_True)
	This and the above algorithms construct a framework for computing the section lines of More...
void	Init1 (const TopoDS_Shape &S1)
	Initializes the first part More...
void	Init1 (const gp_Pln &Pl)
	Initializes the first part More...
void	Init1 (const Handle< Geom_Surface > &Sf)
	Initializes the first part More...
void	Init2 (const TopoDS_Shape &S2)
	initialize second part More...
void	Init2 (const gp_Pln &Pl)
	Initializes the second part More...
void	Init2 (const Handle< Geom_Surface > &Sf)
	This and the above algorithms <br> 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. More...
void	Approximation (const Standard_Boolean B)
	Defines an option for computation of further <br> 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: More...
void	ComputePCurveOn1 (const Standard_Boolean B)
	Indicates if the Pcurve must be (or not) performed on first part. More...
void	ComputePCurveOn2 (const Standard_Boolean B)
	Define options for the computation of further <br> 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. More...
void	Build ()
	Performs the computation of the section lines <br> 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: More...
Standard_Boolean	HasAncestorFaceOn1 (const TopoDS_Shape &E, TopoDS_Shape &F) const
	Identifies the ancestor faces of the new <br> 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: More...
Standard_Boolean	HasAncestorFaceOn2 (const TopoDS_Shape &E, TopoDS_Shape &F) const
	Identifies the ancestor faces of the new <br> 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: More...
Public Member Functions inherited from BRepAlgo_BooleanOperation
virtual void	Delete ()
virtual	~BRepAlgo_BooleanOperation ()
void	PerformDS ()
void	Perform (const TopAbs_State St1, const TopAbs_State St2)
Handle_TopOpeBRepBuild_HBuilder	Builder () const
const TopoDS_Shape &	Shape1 () const
	Returns the first shape involved in this Boolean operation. More...
const TopoDS_Shape &	Shape2 () const
	Returns the second shape involved in this Boolean operation. More...
virtual const TopTools_ListOfShape &	Modified (const TopoDS_Shape &S)
	Returns the list of shapes modified from the shape <S>. More...
virtual Standard_Boolean	IsDeleted (const TopoDS_Shape &S)
	Returns true if the shape S has been deleted. More...
Public Member Functions inherited from BRepBuilderAPI_MakeShape
virtual	~BRepBuilderAPI_MakeShape ()
const TopoDS_Shape &	Shape () const
	Returns a shape built by the shape construction algorithm. <br> Raises exception StdFail_NotDone if the shape was not built. More...
	operator TopoDS_Shape () const
virtual const TopTools_ListOfShape &	Generated (const TopoDS_Shape &S)
	Returns the list of shapes generated from the shape <S>. More...
Public Member Functions inherited from BRepBuilderAPI_Command
virtual	~BRepBuilderAPI_Command ()
virtual Standard_Boolean	IsDone () const
void	Check () const
	Raises NotDone if done is false. More...

Additional Inherited Members
Protected Member Functions inherited from BRepAlgo_BooleanOperation
	BRepAlgo_BooleanOperation (const TopoDS_Shape &S1, const TopoDS_Shape &S2)
	Prepares the operations for S1 and S2. More...
void	BuilderCanWork (const Standard_Boolean B)
Standard_Boolean	BuilderCanWork () const
Protected Member Functions inherited from BRepBuilderAPI_MakeShape
	BRepBuilderAPI_MakeShape ()
Protected Member Functions inherited from BRepBuilderAPI_Command
	BRepBuilderAPI_Command ()
	Set done to False. More...
void	Done ()
	Set done to true. More...
void	NotDone ()
	Set done to false. More...
Protected Attributes inherited from BRepAlgo_BooleanOperation
Handle_TopOpeBRepBuild_HBuilder	myHBuilder
TopoDS_Shape	myS1
TopoDS_Shape	myS2
Protected Attributes inherited from BRepBuilderAPI_MakeShape
TopoDS_Shape	myShape
TopTools_ListOfShape	myGenerated

Detailed Description

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.
  

Constructor & Destructor Documentation

BRepAlgo_Section::BRepAlgo_Section	(	const TopoDS_Shape &	Sh1,
		const TopoDS_Shape &	Sh2,
		const Standard_Boolean	PerformNow = Standard_True
	)

BRepAlgo_Section::BRepAlgo_Section	(	const TopoDS_Shape &	Sh,
		const gp_Pln &	Pl,
		const Standard_Boolean	PerformNow = Standard_True
	)

BRepAlgo_Section::BRepAlgo_Section	(	const TopoDS_Shape &	Sh,
		const Handle< Geom_Surface > &	Sf,
		const Standard_Boolean	PerformNow = Standard_True
	)

BRepAlgo_Section::BRepAlgo_Section	(	const Handle< Geom_Surface > &	Sf,
		const TopoDS_Shape &	Sh,
		const Standard_Boolean	PerformNow = Standard_True
	)

BRepAlgo_Section::BRepAlgo_Section	(	const Handle< Geom_Surface > &	Sf1,
		const Handle< Geom_Surface > &	Sf2,
		const Standard_Boolean	PerformNow = Standard_True
	)

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();
    

Member Function Documentation

void BRepAlgo_Section::Approximation

(

const Standard_Boolean

B

)

 Defines an option for computation of further <br>

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.
  

void BRepAlgo_Section::Build ( )

virtual

  Performs the computation of the section lines <br>

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.
  

Reimplemented from BRepBuilderAPI_MakeShape.

void BRepAlgo_Section::ComputePCurveOn1

(

const Standard_Boolean

B

)

Indicates if the Pcurve must be (or not) performed on first part.

void BRepAlgo_Section::ComputePCurveOn2

(

const Standard_Boolean

B

)

 Define options for the computation of further <br>

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.

Standard_Boolean BRepAlgo_Section::HasAncestorFaceOn1	(	const TopoDS_Shape &	E,
		TopoDS_Shape &	F
	)		const

Identifies the ancestor faces of the new <br>

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.
  

Standard_Boolean BRepAlgo_Section::HasAncestorFaceOn2	(	const TopoDS_Shape &	E,
		TopoDS_Shape &	F
	)		const

 Identifies the ancestor faces of the new <br>

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.
  

void BRepAlgo_Section::Init1

(

const TopoDS_Shape &

S1

)

Initializes the first part

void BRepAlgo_Section::Init1

(

const gp_Pln &

Pl

)

Initializes the first part

void BRepAlgo_Section::Init1

(

const Handle< Geom_Surface > &

Sf

)

Initializes the first part

void BRepAlgo_Section::Init2

(

const TopoDS_Shape &

S2

)

initialize second part

void BRepAlgo_Section::Init2

(

const gp_Pln &

Pl

)

Initializes the second part

void BRepAlgo_Section::Init2

(

const Handle< Geom_Surface > &

Sf

)

 This and the above algorithms <br>

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.

---

The documentation for this class was generated from the following file:

• BRepAlgo_Section.hxx