occt/src/BRepMesh/BRepMesh_GeomTool.hxx

// Copyright (c) 2013 OPEN CASCADE SAS
//
// This file is part of Open CASCADE Technology software library.
//
// This library is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License version 2.1 as published
// by the Free Software Foundation, with special exception defined in the file
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
// distribution for complete text of the license and disclaimer of any warranty.
//
// Alternatively, this file may be used under the terms of Open CASCADE
// commercial license or contractual agreement.

#ifndef _BRepMesh_GeomTool_HeaderFile
#define _BRepMesh_GeomTool_HeaderFile

#include <Standard.hxx>
#include <Standard_DefineAlloc.hxx>
#include <Standard_Macro.hxx>
#include <GCPnts_TangentialDeflection.hxx>
#include <GeomAbs_IsoType.hxx>
#include <TopoDS_Edge.hxx>
#include <Precision.hxx>

class BRepAdaptor_Curve;
class BRepAdaptor_HSurface;
class gp_Pnt;
class gp_Pnt2d;
class gp_Dir;
class BRepMesh_DefaultRangeSplitter;
class Adaptor3d_HSurface;

//! Tool class accumulating common geometrical functions as well as 
//! functionality using shape geometry to produce data necessary for 
//! tessellation.
//! General aim is to calculate discretization points for the given
//! curve or iso curve of surface according to the specified parameters.
class BRepMesh_GeomTool
{
public:

  //! Enumerates states of segments intersection check.
  enum IntFlag
  {
    NoIntersection,
    Cross,
    EndPointTouch,
    PointOnSegment,
    Glued,
    Same
  };

public:

  DEFINE_STANDARD_ALLOC
  
  //! Constructor.
  //! Initiates discretization of the given geometric curve.
  //! @param theCurve curve to be discretized.
  //! @param theFirstParam first parameter of the curve.
  //! @param theLastParam last parameter of the curve.
  //! @param theLinDeflection linear deflection.
  //! @param theAngDeflection angular deflection.
  //! @param theMinPointsNb minimum nuber of points to be produced.
  Standard_EXPORT BRepMesh_GeomTool(
    const BRepAdaptor_Curve& theCurve,
    const Standard_Real      theFirstParam,
    const Standard_Real      theLastParam,
    const Standard_Real      theLinDeflection,
    const Standard_Real      theAngDeflection,
    const Standard_Integer   theMinPointsNb = 2,
    const Standard_Real      theMinSize = Precision::Confusion());
  
  //! Constructor.
  //! Initiates discretization of geometric curve corresponding 
  //! to iso curve of the given surface.
  //! @param theSurface surface the iso curve to be taken from.
  //! @param theIsoType type of iso curve to be used, U or V.
  //! @param theParamIso parameter on the surface specifying the iso curve.
  //! @param theFirstParam first parameter of the curve.
  //! @param theLastParam last parameter of the curve.
  //! @param theLinDeflection linear deflection.
  //! @param theAngDeflection angular deflection.
  //! @param theMinPointsNb minimum nuber of points to be produced.
  Standard_EXPORT BRepMesh_GeomTool(
    const Handle(BRepAdaptor_HSurface)& theSurface,
    const GeomAbs_IsoType               theIsoType,
    const Standard_Real                 theParamIso,
    const Standard_Real                 theFirstParam,
    const Standard_Real                 theLastParam,
    const Standard_Real                 theLinDeflection,
    const Standard_Real                 theAngDeflection,
    const Standard_Integer              theMinPointsNb = 2,
    const Standard_Real                 theMinSize = Precision::Confusion());

  //! Adds point to already calculated points (or replaces existing).
  //! @param thePoint point to be added.
  //! @param theParam parameter on the curve corresponding to the given point.
  //! @param theIsReplace if TRUE replaces existing point lying within 
  //! parameteric tolerance of the given point.
  //! @return index of new added point or found with parametric tolerance
  inline Standard_Integer AddPoint(const gp_Pnt&           thePoint,
                                   const Standard_Real     theParam,
                                   const Standard_Boolean  theIsReplace = Standard_True)
  {
    return myDiscretTool.AddPoint(thePoint, theParam, theIsReplace);
  }
  
  //! Returns number of discretization points.
  inline Standard_Integer NbPoints() const
  {
    return myDiscretTool.NbPoints();
  }
  
  //! Gets parameters of discretization point with the given index.
  //! @param theIndex index of discretization point.
  //! @param theIsoParam parameter on surface to be used as second coordinate 
  //! of resulting 2d point.
  //! @param theParam[out] parameter of the point on the iso curve.
  //! @param thePoint[out] discretization point.
  //! @param theUV[out] discretization point in parametric space of the surface.
  //! @return TRUE on success, FALSE elsewhere.
  Standard_EXPORT Standard_Boolean Value(const Standard_Integer theIndex,
                                         const Standard_Real    theIsoParam,
                                         Standard_Real&         theParam,
                                         gp_Pnt&                thePoint,
                                         gp_Pnt2d&              theUV) const;
  
  //! Gets parameters of discretization point with the given index.
  //! @param theIndex index of discretization point.
  //! @param theSurface surface the curve is lying onto.
  //! @param theParam[out] parameter of the point on the curve.
  //! @param thePoint[out] discretization point.
  //! @param theUV[out] discretization point in parametric space of the surface.
  //! @return TRUE on success, FALSE elsewhere.
  Standard_EXPORT Standard_Boolean Value(const Standard_Integer              theIndex,
                                         const Handle(BRepAdaptor_HSurface)& theSurface,
                                         Standard_Real&                      theParam,
                                         gp_Pnt&                             thePoint,
                                         gp_Pnt2d&                           theUV) const;
  
public: //! @name static API

  //! Computes normal to the given surface at the specified
  //! position in parametric space.
  //! @param theSurface surface the normal should be found for.
  //! @param theParamU U parameter in parametric space of the surface.
  //! @param theParamV V parameter in parametric space of the surface.
  //! @param[out] thePoint 3d point corresponding to the given parameters.
  //! @param[out] theNormal normal vector at the point specified by the parameters.
  //! @return FALSE if the normal can not be computed, TRUE elsewhere.
  Standard_EXPORT static Standard_Boolean Normal(
    const Handle(BRepAdaptor_HSurface)& theSurface,
    const Standard_Real                 theParamU,
    const Standard_Real                 theParamV,
    gp_Pnt&                             thePoint,
    gp_Dir&                             theNormal);

  //! Checks intersection between two lines defined by two points.
  //! @param theStartPnt1 start point of first line.
  //! @param theEndPnt1 end point of first line.
  //! @param theStartPnt2 start point of second line.
  //! @param theEndPnt2 end point of second line.
  //! @param[out] theIntPnt point of intersection.
  //! @param[out] theParamOnSegment parameters of intersection point 
  //! corresponding to first and second segment.
  //! @return status of intersection check.
  Standard_EXPORT static IntFlag IntLinLin(
    const gp_XY&  theStartPnt1,
    const gp_XY&  theEndPnt1,
    const gp_XY&  theStartPnt2,
    const gp_XY&  theEndPnt2,
    gp_XY&        theIntPnt,
    Standard_Real (&theParamOnSegment)[2]);

  //! Checks intersection between the two segments. 
  //! Checks that intersection point lies within ranges of both segments.
  //! @param theStartPnt1 start point of first segment.
  //! @param theEndPnt1 end point of first segment.
  //! @param theStartPnt2 start point of second segment.
  //! @param theEndPnt2 end point of second segment.
  //! @param isConsiderEndPointTouch if TRUE EndPointTouch status will be
  //! returned in case if segments are touching by end points, if FALSE
  //! returns NoIntersection flag.
  //! @param isConsiderPointOnSegment if TRUE PointOnSegment status will be
  //! returned in case if end point of one segment lies onto another one, 
  //! if FALSE returns NoIntersection flag.
  //! @param[out] theIntPnt point of intersection.
  //! @return status of intersection check.
  Standard_EXPORT static IntFlag IntSegSeg(
    const gp_XY&           theStartPnt1,
    const gp_XY&           theEndPnt1,
    const gp_XY&           theStartPnt2,
    const gp_XY&           theEndPnt2,
    const Standard_Boolean isConsiderEndPointTouch,
    const Standard_Boolean isConsiderPointOnSegment,
    gp_Pnt2d&              theIntPnt);

  //! Compute deflection of the given segment.
  static Standard_Real SquareDeflectionOfSegment(
    const gp_Pnt& theFirstPoint,
    const gp_Pnt& theLastPoint,
    const gp_Pnt& theMidPoint)
  {
    // 23.03.2010 skl for OCC21645 - change precision for comparison
    if (theFirstPoint.SquareDistance(theLastPoint) > Precision::SquareConfusion())
    {
      gp_Lin aLin(theFirstPoint, gp_Dir(gp_Vec(theFirstPoint, theLastPoint)));
      return aLin.SquareDistance(theMidPoint);
    }

    return theFirstPoint.SquareDistance(theMidPoint);
  }

  // For better meshing performance we try to estimate the acceleration circles grid structure sizes:
  // For each parametric direction (U, V) we estimate firstly an approximate distance between the future points -
  // this estimation takes into account the required face deflection and the complexity of the face.
  // Particularly, the complexity of the faces based on BSpline curves and surfaces requires much more points.
  // At the same time, for planar faces and linear parts of the arbitrary surfaces usually no intermediate points
  // are necessary.
  // The general idea for each parametric direction:
  // cells_count = 2 ^ log10 ( estimated_points_count )
  // For linear parametric direction we fall back to the initial vertex count:
  // cells_count = 2 ^ log10 ( initial_vertex_count )
  Standard_EXPORT static std::pair<Standard_Integer, Standard_Integer> CellsCount (
    const Handle (Adaptor3d_HSurface)&   theSurface,
    const Standard_Integer               theVerticesNb,
    const Standard_Real                  theDeflection,
    const BRepMesh_DefaultRangeSplitter* theRangeSplitter);

private:

  //! Classifies the point in case of coincidence of two vectors.
  //! @param thePoint1 the start point of a segment (base point).
  //! @param thePoint2 the end point of a segment.
  //! @param thePointToCheck the point to classify.
  //! @return zero value if point is out of segment and non zero value 
  //! if point is between the first and the second point of segment.
  static Standard_Integer classifyPoint (const gp_XY& thePoint1,
                                         const gp_XY& thePoint2,
                                         const gp_XY& thePointToCheck);

private:

  const TopoDS_Edge*                  myEdge;
  GCPnts_TangentialDeflection         myDiscretTool;
  GeomAbs_IsoType                     myIsoType;
};

#endif