0026440: Invalid shape as a result of solid construction in BRepOffset_MakeOffset

Fixed degeneration in wall building in thicksolid mode.

Minor correction.

Test cases for issue CR26440

src/BRepOffset/BRepOffset_MakeOffset.cxx

@@ -109,6 +109,8 @@
 #include <TopTools_MapIteratorOfMapOfShape.hxx>
 #include <TopTools_MapOfShape.hxx>
 #include <TopTools_SequenceOfShape.hxx>
+#include <BRepBuilderAPI_Sewing.hxx>
+#include <Geom_Line.hxx>
 
 #include <stdio.h>
 // POP for NT
@@ -524,6 +526,7 @@ void BRepOffset_MakeOffset::Initialize(const TopoDS_Shape&    S,
   myJoin       = Join;
   myThickening = Thickening;
   myDone     = Standard_False;
+  myIsPerformSewing = Standard_False;
   Clear();
 }
 
@@ -659,6 +662,7 @@ static void EvalMax(const TopoDS_Shape& S, Standard_Real& Tol)
   }
 }
 
+
 //=======================================================================
 //function : MakeOffsetShape
 //purpose  : 
@@ -778,6 +782,21 @@ void BRepOffset_MakeOffset::MakeOffsetShape()
 
   CorrectConicalFaces();
 
+  // Result solid should be computed in MakeOffset scope.
+  if (myThickening &&
+      myIsPerformSewing)
+  {
+    BRepBuilderAPI_Sewing aSew(myTol);
+    aSew.Add(myOffsetShape);
+    aSew.Perform();
+    myOffsetShape = aSew.SewedShape();
+
+    // Rebuild solid.
+    // Offset shape expected to be really closed after sewing.
+    myOffsetShape.Closed(Standard_True);
+    MakeSolid();
+  }
+
   myDone = Standard_True;
 }
 
@@ -2491,7 +2510,6 @@ static void UpdateInitOffset (BRepAlgo_Image&         myInitOffset,
 //function : MakeMissingWalls
 //purpose  : 
 //=======================================================================
-
 void BRepOffset_MakeOffset::MakeMissingWalls ()
 {
   TopTools_DataMapOfShapeListOfShape Contours; //Start vertex + list of connected edges (free boundary)
@@ -2510,23 +2528,61 @@ void BRepOffset_MakeOffset::MakeMissingWalls ()
     Standard_Boolean FirstStep = Standard_True;
     TopoDS_Edge PrevEdge;
     TopoDS_Vertex PrevVertex = StartVertex;
+    Standard_Boolean isBuildFromScratch = Standard_False; // Problems with edges.
     for (; itl.More(); itl.Next())
     {
       TopoDS_Edge anEdge = TopoDS::Edge(itl.Value());
+
+      // Check for offset existence.
       if (!myInitOffsetEdge.HasImage(anEdge))
         continue;
-	  //if (BRep_Tool::Degenerated(anEdge))
+
-	    //continue;
+      // Check for existence of two different vertices.
-	  TopoDS_Face aFace = TopoDS::Face(MapEF(anEdge));
-	  //TopoDS_Edge OE = TopoDS::Edge(myInitOffsetEdge.Image(anEdge).First());
       TopTools_ListOfShape LOE, LOE2;
       myInitOffsetEdge.LastImage( anEdge, LOE );
       myImageOffset.LastImage( LOE.Last(), LOE2 );
       TopoDS_Edge OE = TopoDS::Edge( LOE2.Last() );
-	  ////////////////////////////////////////////////////////////////////////
       TopoDS_Vertex V1, V2, V3, V4;
-	  TopExp::Vertices(anEdge, V1, V2/*, Standard_True*/);
+      TopExp::Vertices(OE,     V4, V3);
-	  TopExp::Vertices(OE,     V4, V3/*, Standard_True*/);
+      TopExp::Vertices(anEdge, V1, V2);
+      Standard_Real aF, aL;
+      const Handle(Geom_Curve) aC = BRep_Tool::Curve(anEdge, aF, aL);
+      if (!aC.IsNull() &&
+         (!aC->IsClosed() && !aC->IsPeriodic()))
+      {
+        gp_Pnt aPntF = BRep_Tool::Pnt(V1);
+        gp_Pnt aPntL = BRep_Tool::Pnt(V2);
+        Standard_Real aDistE = aPntF.SquareDistance(aPntL);
+        if ( aDistE < Precision::SquareConfusion())
+        {
+          // Bad case: non closed, but vertexes mapped to same 3d point.
+          continue;
+        }
+
+        Standard_Real anEdgeTol = BRep_Tool::Tolerance(anEdge);
+        if (aDistE < anEdgeTol)
+        {
+          // Potential problems not detected via checkshape.
+          gp_Pnt aPntOF = BRep_Tool::Pnt(V4);
+          gp_Pnt aPntOL = BRep_Tool::Pnt(V3);
+          if (aPntOF.SquareDistance(aPntOL) > gp::Resolution())
+          {
+            // To avoid computation of complex analytical continuation of Sin / ArcSin.
+            Standard_Real aSinValue = Min(2 * anEdgeTol / aPntOF.Distance(aPntOL), 1.0);
+            Standard_Real aMaxAngle = Min(Abs(ASin(aSinValue)), M_PI_4); // Maximal angle.
+            Standard_Real aCurrentAngle =  gp_Vec(aPntF, aPntL).Angle(gp_Vec(aPntOF, aPntOL));
+            if (aC->IsKind(STANDARD_TYPE(Geom_Line)) &&
+                Abs (aCurrentAngle) > aMaxAngle)
+            {
+              // anEdge not collinear to offset edge.
+              isBuildFromScratch = Standard_True;
+              myIsPerformSewing = Standard_True;
+              continue;
+            }
+          }
+        }
+      }
+
       Standard_Boolean ToReverse = Standard_False;
       if (!V1.IsSame(PrevVertex))
       {
@@ -2534,23 +2590,30 @@ void BRepOffset_MakeOffset::MakeMissingWalls ()
         aVtx = V3; V3 = V4; V4 = aVtx;
         ToReverse = Standard_True;
       }
-	  //Temporary
+
-	  //anEdge.Reverse();
       OE.Orientation(TopAbs::Reverse(anEdge.Orientation()));
       TopoDS_Edge E3, E4;
-	  if (FirstStep)
+      Standard_Boolean ArcOnV2 = ((myJoin == GeomAbs_Arc) && (myInitOffsetEdge.HasImage(V2)));
+      if (FirstStep || isBuildFromScratch)
       {
         E4 = BRepLib_MakeEdge( V1, V4 );
+        if (FirstStep)
           StartEdge = E4;
       }
       else
         E4 = PrevEdge;
-	  Standard_Boolean ArcOnV2 = ((myJoin == GeomAbs_Arc) && (myInitOffsetEdge.HasImage(V2)));
       if (V2.IsSame(StartVertex) && !ArcOnV2)
         E3 = StartEdge;
       else
         E3 = BRepLib_MakeEdge( V2, V3 );
       E4.Reverse();
+
+      if (isBuildFromScratch)
+      {
+        E3.Reverse();
+        E4.Reverse();
+      }
+
       TopoDS_Shape localAnEdge = anEdge.Oriented(TopAbs_FORWARD);
       const TopoDS_Edge& anEdgeFWD = TopoDS::Edge(localAnEdge);
       Standard_Real ParV1 = BRep_Tool::Parameter(V1, anEdgeFWD);
@@ -2572,6 +2635,7 @@ void BRepOffset_MakeOffset::MakeMissingWalls ()
         BB.Add(theWire, OE);
         BB.Add(theWire, E4);
       }
+
       BRepLib::BuildCurves3d( theWire, myTol );
       theWire.Closed(Standard_True);
       TopoDS_Face NewFace;
@@ -2850,10 +2914,19 @@ void BRepOffset_MakeOffset::MakeMissingWalls ()
         PrevVertex = V2;
       }
       else
+      {
+        if (isBuildFromScratch)
+        {
+          PrevEdge = TopoDS::Edge(E4);
+          PrevVertex = V1;
+          isBuildFromScratch = Standard_False;
+        }
+        else
         {
           PrevEdge = E3;
           PrevVertex = V2;
         }
+      }
       FirstStep = Standard_False;
     }
   }

src/BRepOffset/BRepOffset_MakeOffset.hxx

@@ -161,6 +161,7 @@ private:
   Standard_Boolean myDone;
   BRepOffset_Error myError;
   BRepOffset_MakeLoops myMakeLoops;
+  Standard_Boolean myIsPerformSewing; // Handle bad walls in thicksolid mode.
 
 
 };

tests/bugs/modalg_6/bug26440_1

@@ -0,0 +1,29 @@
+puts "============"
+puts "CR26440"
+puts "============"
+puts ""
+##########################################################################################################
+# Invalid shape as a result of solid construction in BRepOffset_MakeOffset
+##########################################################################################################
+
+restore [locate_data_file bug26440_plate.brep] sh1
+
+thickshell result sh1 160
+
+set square 2.40831e+07
+
+set nbshapes_expected "
+Number of shapes in shape
+ VERTEX    : 196
+ EDGE      : 308
+ WIRE      : 110
+ FACE      : 110
+ SHELL     : 1
+ SOLID     : 1
+ COMPSOLID : 0
+ COMPOUND  : 0
+ SHAPE     : 726
+"
+checknbshapes result -ref ${nbshapes_expected} -t -m "solid construction"
+
+set 3dviewer 1

tests/bugs/modalg_6/bug26440_2

@@ -0,0 +1,29 @@
+puts "============"
+puts "CR26440"
+puts "============"
+puts ""
+##########################################################################################################
+# Invalid shape as a result of solid construction in BRepOffset_MakeOffset
+##########################################################################################################
+
+restore [locate_data_file bug26440_plate2.brep] sh1
+
+thickshell result sh1 150 i
+
+set square 5.00111e+06
+
+set nbshapes_expected "
+Number of shapes in shape
+ VERTEX    : 146
+ EDGE      : 225
+ WIRE      : 75
+ FACE      : 75
+ SHELL     : 1
+ SOLID     : 1
+ COMPSOLID : 0
+ COMPOUND  : 0
+ SHAPE     : 523
+"
+checknbshapes result -ref ${nbshapes_expected} -t -m "solid construction"
+
+set 3dviewer 1

tests/bugs/modalg_6/bug26440_3

@@ -0,0 +1,29 @@
+puts "============"
+puts "CR26440"
+puts "============"
+puts ""
+##########################################################################################################
+# Invalid shape as a result of solid construction in BRepOffset_MakeOffset
+##########################################################################################################
+
+restore [locate_data_file bug26440_plate3.brep] sh1
+
+thickshell result sh1 160 i
+
+set square 1.26188e+07
+
+set nbshapes_expected "
+Number of shapes in shape
+ VERTEX    : 88
+ EDGE      : 145
+ WIRE      : 55
+ FACE      : 55
+ SHELL     : 1
+ SOLID     : 1
+ COMPSOLID : 0
+ COMPOUND  : 0
+ SHAPE     : 345
+"
+checknbshapes result -ref ${nbshapes_expected} -t -m "solid construction"
+
+set 3dviewer 1