Implemented a draft of the GZ computation tool

src/Mod/Ship/CMakeLists.txt

@@ -90,6 +90,7 @@ SET(ShipGZ_SRCS
 	shipGZ/PlotAux.py
 	shipGZ/TaskPanel.py
 	shipGZ/TaskPanel.ui
+	shipGZ/Tools.py
 )
 SOURCE_GROUP("shipgz" FILES ${ShipGZ_SRCS})
 

src/Mod/Ship/shipGZ/TaskPanel.py

@@ -27,6 +27,7 @@ import FreeCADGui as Gui
 import Units
 from PySide import QtGui, QtCore
 import PlotAux
+import Tools
 from shipUtils import Paths
 import shipUtils.Units as USys
 import shipUtils.Locale as Locale
@@ -40,6 +41,26 @@ class TaskPanel:
         if self.lc is None:
             return False
         self.save()
+
+        mw = self.getMainWindow()
+        form = mw.findChild(QtGui.QWidget, "TaskPanel")
+        form.angle = self.widget(QtGui.QLineEdit, "Angle")
+        form.n_points = self.widget(QtGui.QSpinBox, "NumPoints")
+        form.var_trim = self.widget(QtGui.QCheckBox, "VariableTrim")
+
+        rolls = []
+        roll = Units.Quantity(Locale.fromString(
+            form.angle.text())).getValueAs('deg').Value
+        n_points = form.n_points.value()
+        for i in range(n_points):
+            rolls.append(roll * i / float(n_points - 1))
+
+        gz = Tools.solve(self.ship,
+                         self.weights,
+                         self.tanks
+                         rolls,
+                         form.var_trim.isChecked())
+
         return True
 
     def reject(self):
@@ -72,7 +93,6 @@ class TaskPanel:
 
         form.angle = self.widget(QtGui.QLineEdit, "Angle")
         form.n_points = self.widget(QtGui.QSpinBox, "NumPoints")
-        form.var_draft = self.widget(QtGui.QCheckBox, "VariableDraft")
         form.var_trim = self.widget(QtGui.QCheckBox, "VariableTrim")
         self.form = form
         if self.initValues():
@@ -278,7 +298,6 @@ class TaskPanel:
         form = mw.findChild(QtGui.QWidget, "TaskPanel")
         form.angle = self.widget(QtGui.QLineEdit, "Angle")
         form.n_points = self.widget(QtGui.QSpinBox, "NumPoints")
-        form.var_draft = self.widget(QtGui.QCheckBox, "VariableDraft")
         form.var_trim = self.widget(QtGui.QCheckBox, "VariableTrim")
         form.angle.setText(Locale.toString(angle_format.format(90.0)))
         # Try to use saved values
@@ -295,14 +314,6 @@ class TaskPanel:
             form.n_points.setValue(self.ship.GZNumPoints)
         except ValueError:
             pass
-        try:
-            props.index("GZVariableDraft")
-            if self.ship.GZVariableDraft:
-                form.var_draft.setCheckState(QtCore.Qt.Checked)
-            else:
-                form.var_draft.setCheckState(QtCore.Qt.Unchecked)
-        except ValueError:
-            pass
         try:
             props.index("GZVariableTrim")
             if self.ship.GZVariableTrim:
@@ -336,20 +347,6 @@ class TaskPanel:
                 "Number of points",
                 None,
                 QtGui.QApplication.UnicodeUTF8))
-        self.widget(QtGui.QCheckBox, "VariableDraft").setText(
-            QtGui.QApplication.translate(
-                "ship_gz",
-                "Variable draft",
-                None,
-                QtGui.QApplication.UnicodeUTF8))
-        self.widget(QtGui.QCheckBox, "VariableDraft").setToolTip(
-            QtGui.QApplication.translate(
-                "ship_gz",
-                "The ship will be moved to the equilibrium draft for each" + \
-                " roll angle. It will significantly increase the required" + \
-                " computing time",
-                None,
-                QtGui.QApplication.UnicodeUTF8))
         self.widget(QtGui.QCheckBox, "VariableTrim").setText(
             QtGui.QApplication.translate(
                 "ship_gz",
@@ -371,13 +368,11 @@ class TaskPanel:
         form = mw.findChild(QtGui.QWidget, "TaskPanel")
         form.angle = self.widget(QtGui.QLineEdit, "Angle")
         form.n_points = self.widget(QtGui.QSpinBox, "NumPoints")
-        form.var_draft = self.widget(QtGui.QCheckBox, "VariableDraft")
         form.var_trim = self.widget(QtGui.QCheckBox, "VariableTrim")
 
         angle = Units.Quantity(Locale.fromString(
             form.angle.text())).getValueAs('deg').Value
         n_points = form.n_points.value()
-        var_draft = form.var_draft.isChecked()
         var_trim = form.var_trim.isChecked()
 
         props = self.ship.PropertiesList
@@ -413,22 +408,6 @@ class TaskPanel:
                                   "Ship",
                                   tooltip)
         self.ship.GZNumPoints = n_points
-        try:
-            props.index("GZVariableDraft")
-        except ValueError:
-            try:
-                tooltip = str(QtGui.QApplication.translate(
-                    "ship_areas",
-                    "GZ curve tool variable draft selection",
-                    None,
-                    QtGui.QApplication.UnicodeUTF8))
-            except:
-                tooltip = "GZ curve tool variable draft selection"
-            self.ship.addProperty("App::PropertyBool",
-                                  "GZVariableDraft",
-                                  "Ship",
-                                  tooltip)
-        self.ship.GZVariableDraft = var_draft
         try:
             props.index("GZVariableTrim")
         except ValueError:

src/Mod/Ship/shipGZ/TaskPanel.ui

@@ -33,16 +33,6 @@
        </property>
       </widget>
      </item>
-     <item row="2" column="0" colspan="2">
-      <widget class="QCheckBox" name="VariableDraft">
-       <property name="text">
-        <string>Variable Draft</string>
-       </property>
-       <property name="checked">
-        <bool>true</bool>
-       </property>
-      </widget>
-     </item>
      <item row="0" column="0">
       <widget class="QLabel" name="AngleLabel">
        <property name="sizePolicy">
@@ -59,7 +49,7 @@
      <item row="0" column="1">
       <widget class="Gui::InputField" name="Angle"/>
      </item>
-     <item row="3" column="0" colspan="2">
+     <item row="2" column="0" colspan="2">
       <widget class="QCheckBox" name="VariableTrim">
        <property name="text">
         <string>Variable Trim angle</string>

src/Mod/Ship/shipGZ/Tools.py

@@ -0,0 +1,143 @@
+#***************************************************************************
+#*                                                                         *
+#*   Copyright (c) 2011, 2012                                              *
+#*   Jose Luis Cercos Pita <jlcercos@gmail.com>                            *
+#*                                                                         *
+#*   This program is free software; you can redistribute it and/or modify  *
+#*   it under the terms of the GNU Lesser General Public License (LGPL)    *
+#*   as published by the Free Software Foundation; either version 2 of     *
+#*   the License, or (at your option) any later version.                   *
+#*   for detail see the LICENCE text file.                                 *
+#*                                                                         *
+#*   This program is distributed in the hope that it will be useful,       *
+#*   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+#*   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+#*   GNU Library General Public License for more details.                  *
+#*                                                                         *
+#*   You should have received a copy of the GNU Library General Public     *
+#*   License along with this program; if not, write to the Free Software   *
+#*   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  *
+#*   USA                                                                   *
+#*                                                                         *
+#***************************************************************************
+
+import math
+from FreeCAD import Vector, Matrix, Placement
+import Part
+import Units
+import FreeCAD as App
+import FreeCADGui as Gui
+import Instance as ShipInstance
+import WeightInstance
+import TankInstance
+from shipHydrostatics import Tools as Hydrostatics
+
+
+G = 9.81
+MAX_EQUILIBRIUM_ITERS = 10
+DENS = 1.025  # [tons/m3], salt water
+
+
+def solve(ship, weights, tanks, rolls, var_trim=True):
+    """ Compute the ship GZ curve.
+    @param ship Ship instance.
+    @param weights Considered weights.
+    @param tanks Considered tanks.
+    @param rolls List of considered roll angles.
+    @param var_trim True if the trim angle should be recomputed at each roll
+    angle, False otherwise.
+    @return GZ values for each roll angle
+    """
+    # Get the unloaded weight (ignoring the tanks for the moment).
+    W = 0.0
+    COG = Vector()
+    for w in weights:
+        W += w.Proxy.getMass(w).getValueAs('kg').Value
+        m = w.Proxy.getMoment(w)
+        COG.x += m[0].getValueAs('kg*m').Value
+        COG.y += m[1].getValueAs('kg*m').Value
+        COG.z += m[2].getValueAs('kg*m').Value
+    COG = COG.multiply(1.0 / W)
+    W = W * G
+
+    # Get the tanks weight
+    TW = 0.0
+    for t in tanks:
+        # t[0] = tank object
+        # t[1] = load density
+        # t[2] = filling level
+        vol = t[0].Proxy.setFillingLevel(t[0], t[2]).getValueAs('m^3').Value
+        TW += vol * t[1]
+    TW = TW.getValueAs('kg').Value * G
+
+    gzs = []
+    for roll in rolls:
+        gz = solve_point(W, COG, TW, ship, tanks, roll, var_trim)
+        if gz is None:
+            return []
+        gzs.append(solve_point(W, COG, TW, ship, tanks, roll, var_trim))
+
+    return gzs
+
+def solve_point(W, COG, TW, ship, tanks, roll, var_trim=True):
+    """ Compute the ship GZ value.
+    @param W Empty ship weight.
+    @param COG Empty ship Center of mass.
+    @param tanks Considered tanks.
+    @param roll Roll angle.
+    @param var_trim True if the trim angle should be recomputed at each roll
+    angle, False otherwise.
+    @return GZ value
+    """
+    gz = 0.0
+    
+    # Look for the equilibrium draft (and eventually the trim angle too)
+    max_draft = ship.Shape.BoundBox.ZMax
+    draft = max_draft
+    max_disp = ship.Shape.Volume.getValueAs('m^3').Value * DENS * 1000.0 * G
+    if max_disp < W + TW:
+        msg = QtGui.QApplication.translate(
+            "ship_console",
+            "Too much weight! The ship will never displace water enough",
+            None,
+            QtGui.QApplication.UnicodeUTF8)
+        App.Console.PrintError(msg + ' ({} tons vs. {} tons)\n'.format(
+            max_disp / 1000.0 / G, (W + TW) / 1000.0 / G))
+        return None
+    trim = 0.0
+    for i in range(MAX_EQUILIBRIUM_ITERS):
+        # Get the displacement, and the bouyance application point
+        disp, B, Cb = Hydrostatics.displacement(ship, draft, roll, trim)
+        disp *= 1000.0 * G
+        # Get the empty ship weight transformed application point
+        p = Part.makePoint(COG)
+        p.translate(Vector(0.0, 0.0, -draft))
+        m = Matrix()
+        m.rotateX(math.radians(roll))
+        m.rotateY(-math.radians(trim))
+        p.rotate(Placement(m))
+        # Add the tanks
+        # TODO
+        # ---
+
+        # Compute the errors
+        draft_error = abs(disp - W - TW) / max_disp
+        if not var_trim:
+            trim_error = 0.0
+        else:
+            dx = B.x - p.X 
+            dz = B.z - p.Z
+            if abs(dx) < 0.001 * ship.Length.getValueAs('m').Value:
+                trim_error = 0.0
+            else:
+                trim_error = math.degrees(math.atan2(dz, dx))
+
+        # Check if we can tolerate the errors
+        if draft_error < 0.01 and trim_error < 1.0:
+            break
+
+        # Get the new draft and trim
+        draft += draft_error * max_draft
+        trim += 0.5 * trim_error
+
+    return B.y - p.Y