0028112: Exception during offset computation

Methods D0, D1, D2, D3, DN of the class GeomEvaluator_OffsetSurface are extended by additional tweak to compensate failure of normal calculation in degenerated points on triangular surfaces.
If the point where normal has failed to calculate is located on parametric boundary of the base surface, one more attempt is made with the point shifted towards interior by Precision::PConfusion().

diff --git a/src/GeomEvaluator/GeomEvaluator_OffsetSurface.cxx b/src/GeomEvaluator/GeomEvaluator_OffsetSurface.cxx
index 82fcf8c6e211388154f7db68b02fc0ed58f7ba48..47b1fac738aa46a65d68ec6424eae742595be91a 100644 (file)
--- a/src/GeomEvaluator/GeomEvaluator_OffsetSurface.cxx
+++ b/src/GeomEvaluator/GeomEvaluator_OffsetSurface.cxx
@@ -72,12 +72,90 @@ GeomEvaluator_OffsetSurface::GeomEvaluator_OffsetSurface(
 {
 }
 
+// If point is on parametric boundary, and calculation of normal fails,
+// try shifting it towards the inside in the hope that derivatives 
+// are better defined there.
+//
+// NB: temporarily this is made as static function and not class method, 
+// hence code duplications
+static Standard_Boolean shiftPoint (Standard_Real& theU, Standard_Real& theV, 
+                                    const Handle(Geom_Surface)& theSurf,
+                                    const Handle(GeomAdaptor_HSurface)& theAdaptor)
+{
+  // Get parametric bounds and closure status
+  Standard_Real aUMin, aUMax, aVMin, aVMax;
+  Standard_Boolean isUPeriodic, isVPeriodic;
+  if (! theSurf.IsNull())
+  {
+    theSurf->Bounds (aUMin, aUMax, aVMin, aVMax);
+    isUPeriodic = theSurf->IsUPeriodic();
+    isVPeriodic = theSurf->IsVPeriodic();
+  }
+  else
+  {
+    aUMin = theAdaptor->FirstUParameter();
+    aUMax = theAdaptor->LastUParameter();
+    aVMin = theAdaptor->FirstVParameter();
+    aVMax = theAdaptor->LastVParameter();
+    isUPeriodic = theAdaptor->IsUPeriodic();
+    isVPeriodic = theAdaptor->IsVPeriodic();
+  }
+
+  Standard_Boolean isShifted = Standard_False;
+
+  // shift by U
+  if (! isUPeriodic && aUMax - aUMin > 2 * Precision::PConfusion())
+  {
+    if (Abs (theU - aUMin) < Precision::PConfusion())
+    {
+      theU += Precision::PConfusion();
+      isShifted = Standard_True;
+    }
+    else if (Abs (theU - aUMax) < Precision::PConfusion())
+    {
+      theU -= Precision::PConfusion();
+      isShifted = Standard_True;
+    }
+  }
+
+  // shift by V
+  if (! isVPeriodic && aVMax - aVMin > 2 * Precision::PConfusion())
+  {
+    if (Abs (theV - aVMin) < Precision::PConfusion())
+    {
+      theV += Precision::PConfusion();
+      isShifted = Standard_True;
+    }
+    else if (Abs (theV - aVMax) < Precision::PConfusion())
+    {
+      theV -= Precision::PConfusion();
+      isShifted = Standard_True;
+    }
+  }
+
+  return isShifted;
+}
+
 void GeomEvaluator_OffsetSurface::D0(
     const Standard_Real theU, const Standard_Real theV, gp_Pnt& theValue) const
 {
   gp_Vec aD1U, aD1V;
   BaseD1(theU, theV, theValue, aD1U, aD1V);
-  CalculateD0(theU, theV, theValue, aD1U, aD1V);
+  try 
+  {
+    CalculateD0(theU, theV, theValue, aD1U, aD1V);
+  } 
+  catch (Geom_UndefinedValue&)
+  {
+    // if failed at parametric boundary, try taking derivative at shifted point
+    Standard_Real aU = theU, aV = theV;
+    if (! shiftPoint (aU, aV, myBaseSurf, myBaseAdaptor))
+    {
+      throw;
+    }
+    BaseD1(aU, aV, theValue, aD1U, aD1V);
+    CalculateD0(theU, theV, theValue, aD1U, aD1V);
+  }
 }
 
 void GeomEvaluator_OffsetSurface::D1(
@@ -86,7 +164,21 @@ void GeomEvaluator_OffsetSurface::D1(
 {
   gp_Vec aD2U, aD2V, aD2UV;
   BaseD2(theU, theV, theValue, theD1U, theD1V, aD2U, aD2V, aD2UV);
-  CalculateD1(theU, theV, theValue, theD1U, theD1V, aD2U, aD2V, aD2UV);
+  try 
+  {
+    CalculateD1(theU, theV, theValue, theD1U, theD1V, aD2U, aD2V, aD2UV);
+  } 
+  catch (Geom_UndefinedValue&)
+  {
+    // if failed at parametric boundary, try taking derivative at shifted point
+    Standard_Real aU = theU, aV = theV;
+    if (! shiftPoint (aU, aV, myBaseSurf, myBaseAdaptor))
+    {
+      throw;
+    }
+    BaseD2 (aU, aV, theValue, theD1U, theD1V, aD2U, aD2V, aD2UV);
+    CalculateD1(theU, theV, theValue, theD1U, theD1V, aD2U, aD2V, aD2UV);
+  }
 }
 
 void GeomEvaluator_OffsetSurface::D2(
@@ -97,8 +189,24 @@ void GeomEvaluator_OffsetSurface::D2(
   gp_Vec aD3U, aD3V, aD3UUV, aD3UVV;
   BaseD3(theU, theV, theValue, theD1U, theD1V,
          theD2U, theD2V, theD2UV, aD3U, aD3V, aD3UUV, aD3UVV);
-  CalculateD2(theU, theV, theValue, theD1U, theD1V,
-              theD2U, theD2V, theD2UV, aD3U, aD3V, aD3UUV, aD3UVV);
+  try
+  {
+    CalculateD2(theU, theV, theValue, theD1U, theD1V,
+                theD2U, theD2V, theD2UV, aD3U, aD3V, aD3UUV, aD3UVV);
+  } 
+  catch (Geom_UndefinedValue&)
+  {
+    // if failed at parametric boundary, try taking derivative at shifted point
+    Standard_Real aU = theU, aV = theV;
+    if (! shiftPoint (aU, aV, myBaseSurf, myBaseAdaptor))
+    {
+      throw;
+    }
+    BaseD3(theU, theV, theValue, theD1U, theD1V,
+         theD2U, theD2V, theD2UV, aD3U, aD3V, aD3UUV, aD3UVV);
+    CalculateD2(theU, theV, theValue, theD1U, theD1V,
+                theD2U, theD2V, theD2UV, aD3U, aD3V, aD3UUV, aD3UVV);
+  }
 }
 
 void GeomEvaluator_OffsetSurface::D3(
@@ -109,8 +217,24 @@ void GeomEvaluator_OffsetSurface::D3(
 {
   BaseD3(theU, theV, theValue, theD1U, theD1V,
          theD2U, theD2V, theD2UV, theD3U, theD3V, theD3UUV, theD3UVV);
-  CalculateD3(theU, theV, theValue, theD1U, theD1V,
-              theD2U, theD2V, theD2UV, theD3U, theD3V, theD3UUV, theD3UVV);
+  try
+  {
+    CalculateD3(theU, theV, theValue, theD1U, theD1V,
+                theD2U, theD2V, theD2UV, theD3U, theD3V, theD3UUV, theD3UVV);
+  } 
+  catch (Geom_UndefinedValue&)
+  {
+    // if failed at parametric boundary, try taking derivative at shifted point
+    Standard_Real aU = theU, aV = theV;
+    if (! shiftPoint (aU, aV, myBaseSurf, myBaseAdaptor))
+    {
+      throw;
+    }
+    BaseD3(aU, aV, theValue, theD1U, theD1V,
+         theD2U, theD2V, theD2UV, theD3U, theD3V, theD3UUV, theD3UVV);
+    CalculateD3(theU, theV, theValue, theD1U, theD1V,
+                theD2U, theD2V, theD2UV, theD3U, theD3V, theD3UUV, theD3UVV);
+  }
 }
 
 gp_Vec GeomEvaluator_OffsetSurface::DN(
@@ -125,7 +249,21 @@ gp_Vec GeomEvaluator_OffsetSurface::DN(
   gp_Pnt aP;
   gp_Vec aD1U, aD1V;
   BaseD1(theU, theV, aP, aD1U, aD1V);
-  return CalculateDN(theU, theV, theDerU, theDerV, aD1U, aD1V);
+  try
+  {
+    return CalculateDN(theU, theV, theDerU, theDerV, aD1U, aD1V);
+  } 
+  catch (Geom_UndefinedValue&)
+  {
+    // if failed at parametric boundary, try taking derivative at shifted point
+    Standard_Real aU = theU, aV = theV;
+    if (! shiftPoint (aU, aV, myBaseSurf, myBaseAdaptor))
+    {
+      throw;
+    }
+    BaseD1 (aU, aV, aP, aD1U, aD1V);
+    return CalculateDN (theU, theV, theDerU, theDerV, aD1U, aD1V);
+  }
 }
 
 

diff --git a/tests/bugs/modalg_7/bug28112 b/tests/bugs/modalg_7/bug28112
new file mode 100644 (file)
index 0000000..ba109f3
--- /dev/null
+++ b/tests/bugs/modalg_7/bug28112
@@ -0,0 +1,22 @@
+puts "========"
+puts "OCC28112"
+puts "========"
+puts ""
+####################################################################################
+## Exception during offset computation
+####################################################################################
+
+restore [locate_data_file bug28112.brep] s
+
+regexp {Mass +: +([-0-9.+eE]+)} [lprops s 1.e-4] full s_len
+regexp {Mass +: +([-0-9.+eE]+)} [sprops s 1.e-4] full s_area
+
+for {set i -5} {$i <= 5} {incr i} {
+  set offsetvalue [expr 6. * $i]
+  offsetshapesimple result s ${offsetvalue}
+
+  checkshape result
+  checkprops result -l ${s_len}
+  checkprops result -s ${s_area}
+  checknbshapes result -vertex 12 -edge 15 -face 3
+}