From 49dc28c54cd2bc7e14fbcdf3795f62bcd6d0977a Mon Sep 17 00:00:00 2001
From: Bernd Hahnebach <bernd@bimstatik.org>
Date: Mon, 26 Jun 2017 21:26:13 +0100
Subject: [PATCH] FEM: gmsh tool, add CoherenceMesh option to remove duplicate
 vertices, set default to true

---
 src/Mod/Fem/FemGmshTools.py           | 13 ++++++++++++-
 src/Mod/Fem/PyObjects/_FemMeshGmsh.py |  6 ++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/Mod/Fem/FemGmshTools.py b/src/Mod/Fem/FemGmshTools.py
index f61822d748..fd389bd478 100644
--- a/src/Mod/Fem/FemGmshTools.py
+++ b/src/Mod/Fem/FemGmshTools.py
@@ -57,6 +57,11 @@ class FemGmshTools():
         # clmin, CharacteristicLengthMin: float
         self.clmin = Units.Quantity(self.mesh_obj.CharacteristicLengthMin).Value
 
+        # geotol, GeometryTolerance: float, 0.0 = 1e-08
+        self.geotol = Units.Quantity(self.mesh_obj.GeometryTolerance).Value
+        if self.geotol == 0.0:
+            self.geotol = 1e-08
+
         # order
         # known_element_orders = ['1st', '2nd']
         self.order = self.mesh_obj.ElementOrder
@@ -380,7 +385,13 @@ class FemGmshTools():
         geo.write("Mesh.Algorithm3D = " + self.algorithm3D + ";\n")
         geo.write("\n")
         geo.write("// meshing\n")
-        geo.write("Mesh  " + self.dimension + ";\n")
+        # remove duplicate vertices, see https://forum.freecadweb.org/viewtopic.php?f=18&t=21571&start=20#p179443
+        if hasattr(self.mesh_obj, 'CoherenceMesh') and self.mesh_obj.CoherenceMesh is True:
+            geo.write("Geometry.Tolerance = " + str(self.geotol) + "; // set gemetrical tolerance (also used for merging nodes)\n")
+            geo.write("Mesh  " + self.dimension + ";\n")
+            geo.write("Coherence Mesh; // Remove duplicate vertices\n")
+        else:
+            geo.write("Mesh  " + self.dimension + ";\n")
         geo.write("\n")
         geo.write("// save\n")
         geo.write("Mesh.Format = 2;\n")  # unv
diff --git a/src/Mod/Fem/PyObjects/_FemMeshGmsh.py b/src/Mod/Fem/PyObjects/_FemMeshGmsh.py
index 0cf2ebbca3..dddd1cda44 100644
--- a/src/Mod/Fem/PyObjects/_FemMeshGmsh.py
+++ b/src/Mod/Fem/PyObjects/_FemMeshGmsh.py
@@ -78,6 +78,12 @@ class _FemMeshGmsh():
         obj.addProperty("App::PropertyBool", "RecombineAll", "FEM GMSH Mesh Params", "Apply recombination algorithm to all surfaces")
         obj.RecombineAll = False
 
+        obj.addProperty("App::PropertyBool", "CoherenceMesh", "FEM GMSH Mesh Params", "Removes all duplicate mesh vertices")
+        obj.CoherenceMesh = True
+
+        obj.addProperty("App::PropertyLength", "GeometryTolerance", "FEM GMSH Mesh Params", "Gemetrical Tolerance (0.0 = GMSH std = 1e-08 mm)")
+        obj.GeometryTolerance = 1e-06
+
         obj.addProperty("App::PropertyEnumeration", "Algorithm2D", "FEM GMSH Mesh Params", "mesh algorithm 2D")
         obj.Algorithm2D = _FemMeshGmsh.known_mesh_algorithm_2D
         obj.Algorithm2D = 'Automatic'  # ?