Open CASCADE Technology 6.6.0
Public Member Functions
BRepAlgoAPI_Section Class Reference

Computes the intersection of two shapes or geometries.
Geometries can be surfaces of planes.
Geometries are converted to faces
When a geometry has been converted to
topology the created shape can be found using
the methods Shape1 and Shape2 inherited from the class BooleanOperation.
The result (Shape() method) is a compound containing
edges built on intersection curves.
By default, the section is performed immediatly in
class constructors, with default values :
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#include <BRepAlgoAPI_Section.hxx>

Inheritance diagram for BRepAlgoAPI_Section:
Inheritance graph
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Public Member Functions

 BRepAlgoAPI_Section (const TopoDS_Shape &S1, const TopoDS_Shape &S2, const BOPAlgo_PaveFiller &aDSF, const Standard_Boolean PerformNow=Standard_True)
virtual ~BRepAlgoAPI_Section ()
 BRepAlgoAPI_Section (const TopoDS_Shape &Sh1, const TopoDS_Shape &Sh2, const Standard_Boolean PerformNow=Standard_True)
 see upper

 BRepAlgoAPI_Section (const TopoDS_Shape &Sh, const gp_Pln &Pl, const Standard_Boolean PerformNow=Standard_True)
 see upper

 BRepAlgoAPI_Section (const TopoDS_Shape &Sh, const Handle< Geom_Surface > &Sf, const Standard_Boolean PerformNow=Standard_True)
 see upper

 BRepAlgoAPI_Section (const Handle< Geom_Surface > &Sf, const TopoDS_Shape &Sh, const Standard_Boolean PerformNow=Standard_True)
 see upper

 BRepAlgoAPI_Section (const Handle< Geom_Surface > &Sf1, const Handle< Geom_Surface > &Sf2, const Standard_Boolean PerformNow=Standard_True)
 This and the above classes construct a framework for
computing the section lines of:

void Init1 (const TopoDS_Shape &S1)
 initialize first part

void Init1 (const gp_Pln &Pl)
 initialize first part

void Init1 (const Handle< Geom_Surface > &Sf)
 initialize first part

void Init2 (const TopoDS_Shape &S2)
 initialize second part

void Init2 (const gp_Pln &Pl)
 initialize second part

void Init2 (const Handle< Geom_Surface > &Sf)
 Reinitializes 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.

void Approximation (const Standard_Boolean B)
 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:

void ComputePCurveOn1 (const Standard_Boolean B)
 Indicates if the Pcurve must be (or not) performed on first part.

void ComputePCurveOn2 (const Standard_Boolean B)
 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.

void Build ()
 Performs the computation of
section lines between 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:

Standard_Boolean HasAncestorFaceOn1 (const TopoDS_Shape &E, TopoDS_Shape &F) const
 get the face of the first part giving section edge <E>.
Returns True on the 3 following conditions :
1/ <E> is an edge returned by the Shape() method.
2/ First part of section performed is a shape.
3/ <E> is built on a intersection curve (i.e <E>
is not the result of common edges)
When False, F remains untouched.

Standard_Boolean HasAncestorFaceOn2 (const TopoDS_Shape &E, TopoDS_Shape &F) const
 Identifies the ancestor faces of
the 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:


Detailed Description


Constructor & Destructor Documentation

BRepAlgoAPI_Section::BRepAlgoAPI_Section ( const TopoDS_Shape S1,
const TopoDS_Shape S2,
const BOPAlgo_PaveFiller aDSF,
const Standard_Boolean  PerformNow = Standard_True 
)
virtual BRepAlgoAPI_Section::~BRepAlgoAPI_Section ( ) [inline, virtual]
BRepAlgoAPI_Section::BRepAlgoAPI_Section ( const TopoDS_Shape Sh1,
const TopoDS_Shape Sh2,
const Standard_Boolean  PerformNow = Standard_True 
)
BRepAlgoAPI_Section::BRepAlgoAPI_Section ( const TopoDS_Shape Sh,
const gp_Pln Pl,
const Standard_Boolean  PerformNow = Standard_True 
)
BRepAlgoAPI_Section::BRepAlgoAPI_Section ( const TopoDS_Shape Sh,
const Handle< Geom_Surface > &  Sf,
const Standard_Boolean  PerformNow = Standard_True 
)
BRepAlgoAPI_Section::BRepAlgoAPI_Section ( const Handle< Geom_Surface > &  Sf,
const TopoDS_Shape Sh,
const Standard_Boolean  PerformNow = Standard_True 
)
BRepAlgoAPI_Section::BRepAlgoAPI_Section ( const Handle< Geom_Surface > &  Sf1,
const Handle< Geom_Surface > &  Sf2,
const Standard_Boolean  PerformNow = Standard_True 
)
  • two shapes Sh1 and Sh2, or
  • shape Sh and plane Pl, or
  • shape Sh and surface Sf, or
  • surface Sf and shape Sh, or
  • two surfaces Sf1 and Sf2,
    and builds a 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.
    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 intersected face of shape S1,
  • no pcurve in the parametric space of the intersected face of shape S2.
    // TopoDS_Shape S1 = ... , S2 = ... ;
    Standard_Boolean PerformNow = Standard_False;
    BRepAlgoAPI_Section S ( S1, S2, PerformNow );
    S.ComputePCurveOn1 (Standard_True);
    S.Approximation (Standard_True);
    S.Build();
    TopoDS_Shape R = S.Shape();

Member Function Documentation

void BRepAlgoAPI_Section::Approximation ( const Standard_Boolean  B)
  • 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 BRepAlgoAPI_Section::Build ( ) [virtual]
  • 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 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.
    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 BRepAlgoAPI_BooleanOperation.

void BRepAlgoAPI_Section::ComputePCurveOn1 ( const Standard_Boolean  B)
void BRepAlgoAPI_Section::ComputePCurveOn2 ( const Standard_Boolean  B)
Standard_Boolean BRepAlgoAPI_Section::HasAncestorFaceOn1 ( const TopoDS_Shape E,
TopoDS_Shape F 
) const
Standard_Boolean BRepAlgoAPI_Section::HasAncestorFaceOn2 ( const TopoDS_Shape E,
TopoDS_Shape F 
) const
  • HasAncestorFaceOn1 gives the ancestor face in the first shape, and
  • 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 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.
    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 BRepAlgoAPI_Section::Init1 ( const Handle< Geom_Surface > &  Sf)
void BRepAlgoAPI_Section::Init1 ( const gp_Pln Pl)
void BRepAlgoAPI_Section::Init1 ( const TopoDS_Shape S1)
void BRepAlgoAPI_Section::Init2 ( const Handle< Geom_Surface > &  Sf)
void BRepAlgoAPI_Section::Init2 ( const gp_Pln Pl)
void BRepAlgoAPI_Section::Init2 ( const TopoDS_Shape S2)

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