From 0b6a0adb3aa45e0437be8d2e65e9d0f80856df42 Mon Sep 17 00:00:00 2001
From: knosulko <knosulko@opencascade.com>
Date: Thu, 13 Jan 2022 03:17:50 +0300
Subject: [PATCH] 0032767: Mesh - incorrect splitting of edges of seams leading
 to hang [since OCCT 7.4.0]

- fix step by parameter of the edge while split curve in case of seam edges
---
 src/BRepMesh/BRepMesh_ModelPreProcessor.cxx | 85 +++++++++++++++------
 tests/bugs/mesh/bug32767                    |  9 +++
 2 files changed, 72 insertions(+), 22 deletions(-)
 create mode 100644 tests/bugs/mesh/bug32767

diff --git a/src/BRepMesh/BRepMesh_ModelPreProcessor.cxx b/src/BRepMesh/BRepMesh_ModelPreProcessor.cxx
index 5466059a53..4eefa24287 100644
--- a/src/BRepMesh/BRepMesh_ModelPreProcessor.cxx
+++ b/src/BRepMesh/BRepMesh_ModelPreProcessor.cxx
@@ -133,7 +133,7 @@ namespace
         {
           if (aDEdge->GetCurve()->ParametersNb() == 2)
           {
-            if (splitEdge (aDEdge, Abs (getConeStep (aDFace))))
+            if (splitEdge (aDEdge, aDFace, Abs (getConeStep (aDFace))))
             {
               TopLoc_Location aLoc;
               const Handle (Poly_Triangulation)& aTriangulation =
@@ -178,48 +178,89 @@ namespace
     } 
 
     //! Splits 3D and all pcurves accordingly using the specified step.
-    Standard_Boolean splitEdge(const IMeshData::IEdgePtr& theDEdge,
-                               const Standard_Real        theDU) const
+    Standard_Boolean splitEdge(const IMeshData::IEdgePtr&    theDEdge,
+                               const IMeshData::IFaceHandle& theDFace,
+                               const Standard_Real           theDU) const
     {
-      if (!splitCurve<gp_XYZ> (theDEdge->GetCurve (), theDU))
+      TopoDS_Edge aE = theDEdge->GetEdge();
+      const TopoDS_Face& aF = theDFace->GetFace();
+
+      Standard_Real aFParam, aLParam;
+
+      Handle(Geom_Curve) aHC = BRep_Tool::Curve (aE, aFParam, aLParam);
+
+      const IMeshData::IPCurveHandle& aIPC1 = theDEdge->GetPCurve(0);
+      const IMeshData::IPCurveHandle& aIPC2 = theDEdge->GetPCurve(1);
+
+      // Calculate the step by parameter of the curve.
+      const gp_Pnt2d& aFPntOfIPC1 = aIPC1->GetPoint (0);
+      const gp_Pnt2d& aLPntOfIPC1 = aIPC1->GetPoint (aIPC1->ParametersNb() - 1);
+      const Standard_Real aMod = Abs (aFPntOfIPC1.Y() - aLPntOfIPC1.Y());
+
+      if (aMod < gp::Resolution())
       {
         return Standard_False;
       }
 
-      for (Standard_Integer aPCurveIdx = 0; aPCurveIdx < theDEdge->PCurvesNb(); ++aPCurveIdx)
+      const Standard_Real aDT = Abs (aLParam - aFParam) / aMod * theDU;
+
+      if (!splitCurve<gp_Pnt> (aHC, theDEdge->GetCurve(), aDT))
       {
-        splitCurve<gp_XY> (theDEdge->GetPCurve (aPCurveIdx), theDU);
+        return Standard_False;
       }
 
+      // Define two pcurves of the seam-edge.
+      Handle(Geom2d_Curve) aPC1, aPC2;
+      Standard_Real af, al;
+
+      aE.Orientation (TopAbs_FORWARD);
+      aPC1 = BRep_Tool::CurveOnSurface (aE, aF, af, al);
+
+      aE.Orientation (TopAbs_REVERSED);
+      aPC2 = BRep_Tool::CurveOnSurface (aE, aF, af, al);
+
+      if (aPC1.IsNull() || aPC2.IsNull())
+      {
+        return Standard_False;
+      }
+
+      // Select the correct pcurve of the seam-edge.
+      const gp_Pnt2d& aFPntOfPC1 = aPC1->Value (aPC1->FirstParameter());
+
+      if (Abs (aLPntOfIPC1.X() - aFPntOfPC1.X()) > Precision::Confusion())
+      {
+        std::swap (aPC1, aPC2);
+      }
+
+      splitCurve<gp_Pnt2d> (aPC1, aIPC1, aDT);
+      splitCurve<gp_Pnt2d> (aPC2, aIPC2, aDT);
+
       return Standard_True;
     }
 
     //! Splits the given curve using the specified step.
-    template<class PointType, class Curve>
-    Standard_Boolean splitCurve(Curve& theCurve, const Standard_Real theDU) const
+    template<class PointType, class GeomCurve, class Curve>
+    Standard_Boolean splitCurve(GeomCurve&          theGeomCurve, 
+                                Curve&              theCurve, 
+                                const Standard_Real theDT) const
     {
       Standard_Boolean isUpdated = Standard_False;
-      PointType aDir = theCurve->GetPoint(theCurve->ParametersNb() - 1).Coord() - theCurve->GetPoint(0).Coord();
-      const Standard_Real aModulus = aDir.Modulus();
-      if (aModulus < gp::Resolution())
-      {
-        return isUpdated;
-      }
-      aDir /= aModulus;
 
-      const Standard_Real    aLastParam = theCurve->GetParameter(theCurve->ParametersNb() - 1);
-      const Standard_Boolean isReversed = theCurve->GetParameter(0) > aLastParam;  
+      const Standard_Real   aFirstParam = theCurve->GetParameter (0);
+      const Standard_Real    aLastParam = theCurve->GetParameter (theCurve->ParametersNb() - 1);
+      const Standard_Boolean isReversed = aFirstParam > aLastParam;
+
       for (Standard_Integer aPointIdx = 1; ; ++aPointIdx)
       {
-        const Standard_Real aCurrParam = theCurve->GetParameter(0) + aPointIdx * theDU * (isReversed ? -1.0 : 1.0); 
-        if (( isReversed &&  (aCurrParam < aLastParam)) ||
-            (!isReversed && !(aCurrParam < aLastParam)))
+        const Standard_Real aCurrParam = aFirstParam + aPointIdx * theDT * (isReversed ? -1.0 : 1.0);
+        if (( isReversed &&  (aCurrParam - aLastParam < Precision::PConfusion())) ||
+            (!isReversed && !(aCurrParam - aLastParam < - Precision::PConfusion())))
         {
           break;
         }
 
-        theCurve->InsertPoint(theCurve->ParametersNb() - 1,
-          theCurve->GetPoint(0).Translated (aDir * aPointIdx * theDU),
+        theCurve->InsertPoint (theCurve->ParametersNb() - 1,
+          theGeomCurve->Value (aCurrParam),
           aCurrParam);
 
         isUpdated = Standard_True;
diff --git a/tests/bugs/mesh/bug32767 b/tests/bugs/mesh/bug32767
new file mode 100644
index 0000000000..b5e472cfe6
--- /dev/null
+++ b/tests/bugs/mesh/bug32767
@@ -0,0 +1,9 @@
+puts "================"
+puts "0032767: Mesh - incorrect splitting of edges of seams leading to hang \[since OCCT 7.4.0\]	"
+puts "================"
+puts ""
+
+restore [locate_data_file bug32767.brep] s
+tclean s
+incmesh s 0.01
+checktrinfo s -tri 3220 -nod 1770 -defl 0.018398669654253779 -tol_abs_defl 1e-6
\ No newline at end of file