From de9329a6c1dc2ef62b22a03652f9f02a99dd7a51 Mon Sep 17 00:00:00 2001
From: UR-0 <u.r.f.pub.2016@online.de>
Date: Sun, 7 Mar 2021 11:41:31 +0100
Subject: [PATCH] [FEM]implement Gmsh mesh property "MeshSizeFromCurvature"

---
 src/Mod/Fem/femmesh/gmshtools.py              | 11 +++++++++--
 src/Mod/Fem/femobjects/mesh_gmsh.py           |  9 +++++++++
 src/Mod/Fem/femtest/data/elmer/group_mesh.geo |  3 ++-
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/src/Mod/Fem/femmesh/gmshtools.py b/src/Mod/Fem/femmesh/gmshtools.py
index 46f1858a85..87472180f6 100644
--- a/src/Mod/Fem/femmesh/gmshtools.py
+++ b/src/Mod/Fem/femmesh/gmshtools.py
@@ -708,11 +708,17 @@ class GmshTools():
             geo.write("Mesh.CharacteristicLengthMin = " + str(0) + ";\n")
         else:
             geo.write("Mesh.CharacteristicLengthMin = " + str(self.clmin) + ";\n")
+        if hasattr(self.mesh_obj, "MeshSizeFromCurvature"):   
+            geo.write(
+                "Mesh.MeshSizeFromCurvature = " + str(self.mesh_obj.MeshSizeFromCurvature) +
+                "; // number of elements per 2*pi radians, 0 to deactivate\n"
+            )
         geo.write("\n")
         if hasattr(self.mesh_obj, "RecombineAll") and self.mesh_obj.RecombineAll is True:
             geo.write("// other mesh options\n")
             geo.write("Mesh.RecombineAll = 1;\n")
             geo.write("\n")
+            
         geo.write("// optimize the mesh\n")
         # Gmsh tetra optimizer
         if hasattr(self.mesh_obj, "OptimizeStd") and self.mesh_obj.OptimizeStd is True:
@@ -727,15 +733,16 @@ class GmshTools():
         # higher order mesh optimizing
         if hasattr(self.mesh_obj, "HighOrderOptimize") and self.mesh_obj.HighOrderOptimize is True:
             geo.write(
-                "Mesh.HighOrderOptimize = 1;  // for more HighOrderOptimize "
+                "Mesh.HighOrderOptimize = 1; // for more HighOrderOptimize "
                 "parameter check http://gmsh.info/doc/texinfo/gmsh.html\n"
             )
         else:
             geo.write(
-                "Mesh.HighOrderOptimize = 0;  // for more HighOrderOptimize "
+                "Mesh.HighOrderOptimize = 0; // for more HighOrderOptimize "
                 "parameter check http://gmsh.info/doc/texinfo/gmsh.html\n"
             )
         geo.write("\n")
+        
         geo.write("// mesh order\n")
         geo.write("Mesh.ElementOrder = " + self.order + ";\n")
         if self.order == "2":
diff --git a/src/Mod/Fem/femobjects/mesh_gmsh.py b/src/Mod/Fem/femobjects/mesh_gmsh.py
index 6b5ec792e3..90ba9e90ea 100644
--- a/src/Mod/Fem/femobjects/mesh_gmsh.py
+++ b/src/Mod/Fem/femobjects/mesh_gmsh.py
@@ -212,6 +212,15 @@ class MeshGmsh(base_fempythonobject.BaseFemPythonObject):
             # https://forum.freecadweb.org/viewtopic.php?t=41738
             # https://forum.freecadweb.org/viewtopic.php?f=18&t=45260&start=20#p389494
 
+        if not hasattr(obj, "MeshSizeFromCurvature"):
+            obj.addProperty(
+                "App::PropertyIntegerConstraint",
+                "MeshSizeFromCurvature",
+                "FEM Gmsh Mesh Params",
+                "number of elements per 2*pi radians, 0 to deactivate"
+            )
+            obj.MeshSizeFromCurvature = (12, 0, 10000, 1)
+            
         if not hasattr(obj, "Algorithm2D"):
             obj.addProperty(
                 "App::PropertyEnumeration",
diff --git a/src/Mod/Fem/femtest/data/elmer/group_mesh.geo b/src/Mod/Fem/femtest/data/elmer/group_mesh.geo
index 55086c2668..e28df28f6e 100644
--- a/src/Mod/Fem/femtest/data/elmer/group_mesh.geo
+++ b/src/Mod/Fem/femtest/data/elmer/group_mesh.geo
@@ -14,11 +14,12 @@ Physical Volume("Solid1") = {1};
 // min, max Characteristic Length
 Mesh.CharacteristicLengthMax = 1e+22;
 Mesh.CharacteristicLengthMin = 8.0;
+Mesh.MeshSizeFromCurvature = 12; // number of elements per 2*pi radians, 0 to deactivate
 
 // optimize the mesh
 Mesh.Optimize = 1;
 Mesh.OptimizeNetgen = 0;
-Mesh.HighOrderOptimize = 0;  // for more HighOrderOptimize parameter check http://gmsh.info/doc/texinfo/gmsh.html
+Mesh.HighOrderOptimize = 0; // for more HighOrderOptimize parameter check http://gmsh.info/doc/texinfo/gmsh.html
 
 // mesh order
 Mesh.ElementOrder = 2;