[FEM] SI unit fixes for Elmer

- since we use consistently SI units (as recommended my the Elmer forum), we need to scale the input mesh (we use ElmerGrid that has an option fur this purpose)
- Since the result will be in the scaled mesh, we need to scale it back

With this PR, one gets now correct result independent of
- the used unit scheme
- the simulation type (electrical or thermo-mechanical)

src/Mod/Fem/Gui/ViewProviderFemPostObject.cpp

@@ -71,6 +71,7 @@ ViewProviderFemPostObject::ViewProviderFemPostObject() : m_blockPropertyChanges(
     ADD_PROPERTY_TYPE(Field,((long)0), "Coloring", App::Prop_None, "Select the field used for calculating the color");
     ADD_PROPERTY_TYPE(VectorMode,((long)0), "Coloring", App::Prop_None, "Select what to show for a vector field");
     ADD_PROPERTY(Transparency, (0));
+    ADD_PROPERTY(Scale, (1.0));
 
     sPixmap = "fem-femmesh-from-shape";
 
@@ -425,11 +426,19 @@ void ViewProviderFemPostObject::WritePointData(vtkPoints* points, vtkDataArray*
     if(!points)
         return;
 
+    // if the object contains "Elmer" but no scale has been set, we set it to 1000.0
+    // because for Elmer we work with SI units and thus get a scaled result we need to transform
+    auto Label = std::string(pcObject->Label.getValue());
+    auto found = Label.find(std::string("Elmer"));
+    if (found != std::string::npos && Scale.getValue() != 1000.0)
+        Scale.setValue(1000.0);
+
     m_coordinates->point.startEditing();
     m_coordinates->point.setNum(points->GetNumberOfPoints());
+    auto scale = Scale.getValue();
     for (i = 0; i < points->GetNumberOfPoints(); i++) {
         p = points->GetPoint(i);
-        m_coordinates->point.set1Value(i, p[0], p[1], p[2]);
+        m_coordinates->point.set1Value(i, p[0] * scale, p[1] * scale, p[2] * scale);
     }
     m_coordinates->point.finishEditing();
 
@@ -506,8 +515,6 @@ void ViewProviderFemPostObject::WriteTransparency() {
     m_material->transparency.setValue(trans);
 }
 
-
-
 void ViewProviderFemPostObject::updateData(const App::Property* p) {
 
     if( strcmp(p->getName(), "Data") == 0 ) {
@@ -534,22 +541,25 @@ bool ViewProviderFemPostObject::setupPipeline() {
 
 void ViewProviderFemPostObject::onChanged(const App::Property* prop) {
 
-    if(m_blockPropertyChanges)
+    if (m_blockPropertyChanges)
         return;
 
     bool ResetColorBarRange = true;
-    if(prop == &Field && setupPipeline()) {
+    if (prop == &Field && setupPipeline()) {
         updateProperties();
         WriteColorData(ResetColorBarRange);
         WriteTransparency();
     }
-    else if(prop == &VectorMode && setupPipeline()) {
+    else if (prop == &VectorMode && setupPipeline()) {
         WriteColorData(ResetColorBarRange);
         WriteTransparency();
     }
-    else if(prop == &Transparency) {
+    else if (prop == &Transparency) {
         WriteTransparency();
     }
+    else if (prop == &Scale) {
+        update3D();
+    }
 
     ViewProviderDocumentObject::onChanged(prop);
 }

src/Mod/Fem/Gui/ViewProviderFemPostObject.h

@@ -82,6 +82,7 @@ public:
     App::PropertyEnumeration            Field;
     App::PropertyEnumeration            VectorMode;
     App::PropertyPercent                Transparency;
+    App::PropertyFloat                  Scale;
 
     void attach(App::DocumentObject *pcObject);
     void setDisplayMode(const char* ModeName);

src/Mod/Fem/femsolver/elmer/writer.py

@@ -214,7 +214,8 @@ class Writer(object):
                     _ELMERGRID_IFORMAT,
                     _ELMERGRID_OFORMAT,
                     unvPath,
-                    "-out", self.directory]
+                    "-scale", "0.001", "0.001", "0.001",
+                     "-out", self.directory]
             subprocess.call(args, stdout=subprocess.DEVNULL)
 
     def _writeStartinfo(self):
@@ -280,11 +281,12 @@ class Writer(object):
     def _handleSimulation(self):
         self._simulation("Coordinate System", "Cartesian 3D")
         self._simulation("Coordinate Mapping", (1, 2, 3))
-        if self.unit_schema == Units.Scheme.SI2:
-            self._simulation("Coordinate Scaling", 0.001)
-            Console.PrintMessage(
-                "'Coordinate Scaling = Real 0.001' was inserted into the solver input file.\n"
-            )
+        # not necessary anymore since we use SI units
+        #if self.unit_schema == Units.Scheme.SI2:
+        #self._simulation("Coordinate Scaling", 0.001)
+        #    Console.PrintMessage(
+        #        "'Coordinate Scaling = Real 0.001' was inserted into the solver input file.\n"
+        #    )
         self._simulation("Simulation Type", "Steady state")
         self._simulation("Steady State Max Iterations", 1)
         self._simulation("Output Intervals", 1)

src/Mod/Fem/femtest/data/elmer/ccxcantilever_faceload_1_si.sif

@@ -34,7 +34,6 @@ End
 Simulation 
   BDF Order = Integer 1
   Coordinate Mapping(3) = Integer 1 2 3
-  Coordinate Scaling = Real 0.001
   Coordinate System = String "Cartesian 3D"
   Output Intervals = Integer 1
   Simulation Type = String "Steady state"