Fem: Add electrostatic concentrated load

src/Mod/Fem/Gui/Resources/ui/ElectricChargeDensity.ui

@@ -164,6 +164,16 @@
               </property>
              </widget>
             </item>
+            <item row="1" column="0">
+             <widget class="QCheckBox" name="ckb_concentrated">
+              <property name="visible">
+                <bool>false</bool>
+              </property>
+              <property name="text">
+               <string>Concentrated</string>
+              </property>
+             </widget>
+            </item>
            </layout>
           </item>
          </layout>

src/Mod/Fem/femmesh/meshsetsgetter.py

@@ -159,6 +159,7 @@ class MeshSetsGetter:
         self.get_constraints_temperature_nodes()
         self.get_constraints_initialtemperature_nodes()
         self.get_constraints_electrostatic_nodes()
+        self.get_constraints_electricchargedensity_nodes()
 
         # constraints sets with constraint data
         self.get_constraints_force_nodeloads()
@@ -289,6 +290,18 @@ class MeshSetsGetter:
                     self.femmesh, femobj
                 )
 
+    def get_constraints_electricchargedensity_nodes(self):
+        if not self.member.cons_electricchargedensity:
+            return
+        # get nodes
+        for femobj in self.member.cons_electricchargedensity:
+            # femobj --> dict, FreeCAD document object is femobj["Object"]
+            if femobj["Object"].Concentrated:
+                print_obj_info(femobj["Object"])
+                femobj["Nodes"] = meshtools.get_femnodes_by_femobj_with_references(
+                    self.femmesh, femobj
+                )
+
     def get_constraints_force_nodeloads(self):
         if not self.member.cons_force:
             return

src/Mod/Fem/femobjects/constraint_electricchargedensity.py

@@ -31,6 +31,7 @@ __url__ = "https://www.freecad.org"
 
 
 from FreeCAD import Units
+from FreeCAD import Base
 
 from . import base_fempythonobject
 
@@ -77,6 +78,15 @@ class ConstraintElectricChargeDensity(base_fempythonobject.BaseFemPythonObject):
                 value="0 C",
             )
         )
+        prop.append(
+            _PropHelper(
+                type="App::PropertyBool",
+                name="Concentrated",
+                group="Electric Charge Density",
+                doc="Use concentrated charges at the nodes",
+                value=False,
+            )
+        )
         prop.append(
             _PropHelper(
                 type="App::PropertyEnumeration",
@@ -89,6 +99,23 @@ class ConstraintElectricChargeDensity(base_fempythonobject.BaseFemPythonObject):
 
         return prop
 
+    def onDocumentRestored(self, obj):
+        print("restored", obj.Name)
+        # update old project with new properties
+        for prop in self._get_properties():
+            try:
+                obj.getPropertyByName(prop.name)
+            except Base.PropertyError:
+                prop.add_to_object(obj)
+
+    def onChanged(self, obj, prop):
+        print("change", prop)
+        if prop == "Mode":
+            if obj.Mode == "Total Source":
+                obj.setPropertyStatus("Concentrated", "-ReadOnly")
+            else:
+                obj.setPropertyStatus("Concentrated", "ReadOnly")
+
     def get_total_source_density(self, obj):
         """
         Calculate density for `Total Source` mode.

src/Mod/Fem/femsolver/calculix/write_constraint_electricchargedensity.py

@@ -43,6 +43,12 @@ def write_meshdata_constraint(f, femobj, den_obj, ccxwriter):
     if ccxwriter.solver_obj.ElectromagneticMode != "electrostatic":
         return
 
+    if den_obj.Concentrated and den_obj.Mode == "Total Source":
+        f.write(f"*NSET,NSET={den_obj.Name}\n")
+        for n in femobj["Nodes"]:
+            f.write(f"{n},\n")
+        return
+
     if den_obj.Mode in ["Source", "Total Source"]:
         f.write(f"*ELSET,ELSET={den_obj.Name}\n")
         for refs, surf, is_sub_el in femobj["ChargeDensityElements"]:
@@ -73,6 +79,14 @@ def write_constraint(f, femobj, den_obj, ccxwriter):
     if ccxwriter.solver_obj.ElectromagneticMode != "electrostatic":
         return
 
+    if den_obj.Concentrated and den_obj.Mode == "Total Source":
+        nodes = len(femobj["Nodes"])
+        node_charge = den_obj.TotalCharge.getValueAs("C").Value / nodes
+        f.write("*CFLUX\n")
+        f.write("{},11,{:.13G}\n".format(den_obj.Name, node_charge))
+        f.write("\n")
+        return
+
     match den_obj.Mode:
         case "Source":
             density = den_obj.SourceChargeDensity

src/Mod/Fem/femtaskpanels/task_constraint_electricchargedensity.py

@@ -71,11 +71,16 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
             QtCore.SIGNAL("currentIndexChanged(int)"),
             self.mode_changed,
         )
+        QtCore.QObject.connect(
+            self.parameter_widget.ckb_concentrated,
+            QtCore.SIGNAL("toggled(bool)"),
+            self.concentrated_changed,
+        )
 
         # geometry selection widget
         # start with Solid in list!
         self.selection_widget = selection_widgets.GeometryElementsSelection(
-            obj.References, ["Solid", "Face", "Edge"], False, False
+            obj.References, ["Solid", "Face", "Edge", "Vertex"], False, False
         )
 
         # form made from param and selection widget
@@ -109,6 +114,7 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
         self.obj.InterfaceChargeDensity = self.interface_charge_density
         self.obj.TotalCharge = self.total_charge
         self.obj.Mode = self.mode
+        self.obj.Concentrated = self.concentrated
 
         self.selection_widget.finish_selection()
         self.restore_visibility()
@@ -129,6 +135,8 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
         self.source_charge_density = self.obj.SourceChargeDensity
         self.interface_charge_density = self.obj.InterfaceChargeDensity
         self.total_charge = self.obj.TotalCharge
+        self.concentrated = self.obj.Concentrated
+
         FreeCADGui.ExpressionBinding(self.parameter_widget.qsb_source_charge_density).bind(
             self.obj, "SourceChargeDensity"
         )
@@ -155,6 +163,10 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
         self.parameter_widget.cb_mode.setCurrentIndex(index)
         self.mode_changed(index)
 
+        self.parameter_widget.ckb_concentrated.setChecked(self.concentrated)
+        if self.mode == "Total Source":
+            self.parameter_widget.ckb_concentrated.setVisible(True)
+
     def source_charge_density_changed(self, base_quantity_value):
         self.source_charge_density = base_quantity_value
 
@@ -166,6 +178,15 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
 
     def mode_changed(self, index):
         self.mode = self.mode_enum[index]
-        if self.mode in ["Total Interface", "Total Source"]:
-            index = 2
+        match self.mode:
+            case "Total Interface":
+                index = 2
+                self.parameter_widget.ckb_concentrated.setVisible(False)
+            case "Total Source":
+                index = 2
+                self.parameter_widget.ckb_concentrated.setVisible(True)
+
         self.parameter_widget.sw_mode.setCurrentIndex(index)
+
+    def concentrated_changed(self, value):
+        self.concentrated = value