0028848: It is necessary to protect the algorithms from degenerated surfaces of type SurfaceOfLinearExtrusion

Forbid the creation of degenerated SurfaceOfLinearExtrusion in case the basis curve is a line (or BSpline with two points only) and the direction of extrusion is parallel to the direction of the line.

dox/dev_guides/upgrade/upgrade.md

@@ -1391,3 +1391,7 @@ if (anError != Storage_VSOk)
 Since 7.2.0 version, method *IsPeriodic()* returns the corresponding status of periodicity of the basis curve regardless of closure status of the adaptor curve (see method *IsClosed()*).
 Method *IsClosed()* for adaptor can return false even on periodic curve, in the case if its parametric range is not full period, e.g. for adaptor on circle in range [0, @f$ \pi @f$].
 In previous versions, *IsPeriodic()* always returned false if *IsClosed()* returned false.
+
+@subsection upgrade_720_Creation_SurfaceOfLinearExtrusion
+
+Since 7.2.0 version, it will be impossible to create the SurfaceOfLinearExtrusion from the linear basis curve (*Line* or *BSpline* curve with only two poles) in the direction parallel to the direction of that curve. The *Standard_ConstructionError* exception will be thrown in this case.

src/Geom/Geom_SurfaceOfLinearExtrusion.cxx

@@ -64,6 +64,9 @@ typedef gp_Vec  Vec;
 typedef gp_XYZ  XYZ;
 
 
+static
+ Standard_Boolean IsParallel(const Handle(Geom_Curve)& theCurve,
+                             const gp_Dir& theDir);
 
 //=======================================================================
 //function : Copy
@@ -84,15 +87,19 @@ Handle(Geom_Geometry) Geom_SurfaceOfLinearExtrusion::Copy () const
 //purpose  : 
 //=======================================================================
 
-Geom_SurfaceOfLinearExtrusion::Geom_SurfaceOfLinearExtrusion 
-  ( const Handle(Geom_Curve)& C, 
-    const Dir& V) {
-
-   basisCurve = Handle(Geom_Curve)::DownCast(C->Copy());  // Copy 10-03-93
-   direction  = V;
-   smooth     = C->Continuity();
-   myEvaluator = new GeomEvaluator_SurfaceOfExtrusion(basisCurve, direction);
- }
+Geom_SurfaceOfLinearExtrusion::Geom_SurfaceOfLinearExtrusion
+ (const Handle(Geom_Curve)& C,
+  const Dir& V)
+{
+  if (IsParallel(C, V))
+    throw Standard_ConstructionError("Geom_SurfaceOfLinearExtrusion - "
+      "direction of the extrusion coincides with the direction of the basis line");
+  //
+  basisCurve = Handle(Geom_Curve)::DownCast(C->Copy());  // Copy 10-03-93
+  direction = V;
+  smooth = C->Continuity();
+  myEvaluator = new GeomEvaluator_SurfaceOfExtrusion(basisCurve, direction);
+}
 
 
 //=======================================================================
@@ -149,6 +156,9 @@ void Geom_SurfaceOfLinearExtrusion::SetDirection (const Dir& V)
 {
   direction = V;
   myEvaluator->SetDirection(direction);
+  if (!basisCurve.IsNull() && IsParallel(basisCurve, direction))
+    throw Standard_ConstructionError("Geom_SurfaceOfLinearExtrusion::SetDirection - "
+      "direction of the extrusion coincides with the direction of the basis line");
 }
 
 
@@ -158,10 +168,13 @@ void Geom_SurfaceOfLinearExtrusion::SetDirection (const Dir& V)
 //=======================================================================
 
 void Geom_SurfaceOfLinearExtrusion::SetBasisCurve (const Handle(Geom_Curve)& C) {
-
-   smooth = C->Continuity();
-   basisCurve = Handle(Geom_Curve)::DownCast(C->Copy());  // Copy 10-03-93
-   myEvaluator = new GeomEvaluator_SurfaceOfExtrusion(basisCurve, direction);
+  if (IsParallel(C, direction))
+    throw Standard_ConstructionError("Geom_SurfaceOfLinearExtrusion::SetBasisCurve - "
+      "direction of the extrusion coincides with the direction of the basis line");
+  //
+  smooth = C->Continuity();
+  basisCurve = Handle(Geom_Curve)::DownCast(C->Copy());  // Copy 10-03-93
+  myEvaluator = new GeomEvaluator_SurfaceOfExtrusion(basisCurve, direction);
 }
 
 
@@ -391,3 +404,43 @@ gp_GTrsf2d Geom_SurfaceOfLinearExtrusion::ParametricTransformation
  
   return TU * TV;
 }
+
+//=======================================================================
+//function : IsParallel
+//purpose  : Checks if the direction of the given curve is parallel to
+//           the given direction (only lines and BSplines are currently checked)
+//=======================================================================
+Standard_Boolean IsParallel(const Handle(Geom_Curve)& theCurve,
+                            const gp_Dir& theDir)
+{
+  Handle(Geom_Curve) aCurve = theCurve;
+  while (aCurve->IsKind(STANDARD_TYPE(Geom_TrimmedCurve)) ||
+         aCurve->IsKind(STANDARD_TYPE(Geom_OffsetCurve)))
+  {
+    aCurve = aCurve->IsKind(STANDARD_TYPE(Geom_TrimmedCurve)) ?
+      Handle(Geom_TrimmedCurve)::DownCast(aCurve)->BasisCurve() :
+      Handle(Geom_OffsetCurve) ::DownCast(aCurve)->BasisCurve();
+  }
+  //
+  Standard_Boolean bParallel = Standard_False;
+  if (aCurve->IsKind(STANDARD_TYPE(Geom_Line)) ||
+      aCurve->IsKind(STANDARD_TYPE(Geom_BSplineCurve)))
+  {
+    if (aCurve->IsKind(STANDARD_TYPE(Geom_Line)))
+    {
+      gp_Lin aLine = Handle(Geom_Line)::DownCast(aCurve)->Lin();
+      bParallel = aLine.Position().Direction().IsParallel(theDir, Precision::Angular());
+    }
+    else
+    {
+      Handle(Geom_BSplineCurve) aBSplineC = Handle(Geom_BSplineCurve)::DownCast(aCurve);
+      if (aBSplineC->Degree() == 1 && aBSplineC->NbPoles() == 2)
+      {
+        gp_Vec aBSplDir(aBSplineC->Pole(1), aBSplineC->Pole(2));
+        bParallel = (aBSplDir.Magnitude() < gp::Resolution()) ||
+                     aBSplDir.IsParallel(theDir, Precision::Angular());
+      }
+    }
+  }
+  return bParallel;
+}

src/Geom/Geom_SurfaceOfLinearExtrusion.hxx

@@ -43,30 +43,32 @@ DEFINE_STANDARD_HANDLE(Geom_SurfaceOfLinearExtrusion, Geom_SweptSurface)
 //! surface"), e.g. a generalized cylinder. Such a surface
 //! is obtained by sweeping a curve (called the "extruded
 //! curve" or "basis") in a given direction (referred to as
-//! the "direction of extrusion" and defined by a unit vector).
+//! the "direction of extrusion" and defined by a unit vector).<br>
 //! The u parameter is along the extruded curve. The v
 //! parameter is along the direction of extrusion.
 //! The parameter range for the u parameter is defined
 //! by the reference curve.
 //! The parameter range for the v parameter is ] -
 //! infinity, + infinity [.
-//! The position of the curve gives the origin of the v parameter.
-//! The surface is "CN" in the v parametric direction.
+//! The position of the curve gives the origin of the v parameter.<br>
+//! The surface is "CN" in the v parametric direction.<br>
 //! The form of a surface of linear extrusion is generally a
-//! ruled surface (GeomAbs_RuledForm). It can be:
+//! ruled surface (GeomAbs_RuledForm). It can be:<br>
 //! - a cylindrical surface, if the extruded curve is a circle,
 //! or a trimmed circle, with an axis parallel to the
-//! direction of extrusion (GeomAbs_CylindricalForm), or
+//! direction of extrusion (GeomAbs_CylindricalForm), or<br>
 //! - a planar surface, if the extruded curve is a line
-//! (GeomAbs_PlanarForm).
+//! (GeomAbs_PlanarForm).<br>
 //! Note: The surface of extrusion is built from a copy of
 //! the original basis curve, so the original curve is not
-//! modified when the surface is modified.
-//! Warning
-//! Degenerate surfaces are not detected. A degenerate
-//! surface is obtained, for example, when the extruded
-//! curve is a line and the direction of extrusion is parallel
-//! to that line.
+//! modified when the surface is modified.<br>
+//! Warning: Not all cases of the creation of the degenerated
+//! surfaces are detected.<br>
+//! Only the following case is currently detected:<br>
+//! - The extruded curve is a line (or a BSpline with only two poles)
+//! and the direction of extrusion is parallel to that line.<br>
+//! The exception <i>Standard_ConstructionError</> will be thrown in
+//! this case.
 class Geom_SurfaceOfLinearExtrusion : public Geom_SweptSurface
 {
 
@@ -81,18 +83,25 @@ public:
   //! . a cylindrical surface if the extruded curve is a circle or
   //! a trimmed circle (CylindricalForm),
   //! . a plane surface if the extruded curve is a Line (PlanarForm).
-  //! Warnings :
-  //! Degenerated surface cases are not detected. For example if the
-  //! curve C is a line and V is parallel to the direction of this
-  //! line.
+  //! Warning: Not all cases of the creation of the degenerated
+  //! surfaces are detected.<br>
+  //! Only the following case is currently detected:<br>
+  //! - The given curve is a line (or a BSpline with only two poles)
+  //! and the given direction of extrusion is parallel to that line.<br>
+  //! The exception <i>Standard_ConstructionError</> will be thrown in
+  //! this case.
   Standard_EXPORT Geom_SurfaceOfLinearExtrusion(const Handle(Geom_Curve)& C, const gp_Dir& V);
   
   //! Assigns V as the "direction of extrusion" for this
-  //! surface of linear extrusion.
+  //! surface of linear extrusion.<br>
+  //! Throws the exception <i>Standard_ConstructionError</> if the given direction is
+  //! parallel to the direction of the basisCurve.
   Standard_EXPORT void SetDirection (const gp_Dir& V);
   
   //! Modifies this surface of linear extrusion by redefining
-  //! its "basis curve" (the "extruded curve").
+  //! its "basis curve" (the "extruded curve").<br>
+  //! Throws the exception <i>Standard_ConstructionError</> if the direction
+  //! of extrusion is parallel to the direction of the given curve.
   Standard_EXPORT void SetBasisCurve (const Handle(Geom_Curve)& C);
   
   //! Changes the orientation of this surface of linear