Fix/py color support osg viewer (#1398)

* Add color support for dartpy osg Viewer and ImGuiViewer

An Eigen::Vector4f can be passed to the viewer constructor to set the background color.

* Fix implicit conversion from python lists to numpy vector

only works for double vectors

* Add white background color to

* Fix wrong comment

python/dartpy/gui/osg/ImGuiViewer.cpp

@@ -49,6 +49,11 @@ void ImGuiViewer(py::module& m)
       dart::gui::osg::Viewer,
       osg::ref_ptr<dart::gui::osg::ImGuiViewer>>(m, "ImGuiViewer")
       .def(::py::init<>())
+      .def(
+          ::py::init([](const Eigen::Vector4d& clearColor) {
+            return new ::dart::gui::osg::ImGuiViewer(eigToOsgVec4f(clearColor));
+          }),
+          ::py::arg("clearColor"))
       .def(::py::init<const osg::Vec4&>(), ::py::arg("clearColor"))
       .def(
           "getImGuiHandler",

python/dartpy/gui/osg/Viewer.cpp

@@ -59,6 +59,11 @@ void Viewer(py::module& m)
       dart::common::Subject,
       ::osg::ref_ptr<dart::gui::osg::Viewer>>(m, "Viewer")
       .def(::py::init<>())
+      .def(
+          ::py::init([](const Eigen::Vector4f& clearColor) {
+            return new ::dart::gui::osg::Viewer(eigToOsgVec4d(clearColor));
+          }),
+          ::py::arg("clearColor"))
       .def(::py::init<const osg::Vec4&>(), ::py::arg("clearColor"))
       .def(
           "captureScreen",

python/examples/hello_world_gui/main.py

@@ -2,29 +2,29 @@
 
 
 class HelloWorldNode(dart.gui.osg.RealTimeWorldNode):
-  # Use this function to execute custom code before each time that the
-  # window is rendered. This function can be deleted if it does not need
-  # to be used.
-  def customPreRefresh(self):
-    pass
-
-  # Use this function to execute custom code after each time that the
-  # window is rendered. This function can be deleted if it does not need
-  # to be used.
-  def customPostRefresh(self):
-    pass
-
-  # Use this function to execute custom code before each simulation time
-  # step is performed. This function can be deleted if it does not need
-  # to be used.
-  def customPreStep(self):
-    pass
-
-  # Use this function to execute custom code after each simulation time
-  # step is performed. This function can be deleted if it does not need
-  # to be used.
-  def customPostStep(self):
-    pass
+    # Use this function to execute custom code before each time that the
+    # window is rendered. This function can be deleted if it does not need
+    # to be used.
+    def customPreRefresh(self):
+        pass
+
+    # Use this function to execute custom code after each time that the
+    # window is rendered. This function can be deleted if it does not need
+    # to be used.
+    def customPostRefresh(self):
+        pass
+
+    # Use this function to execute custom code before each simulation time
+    # step is performed. This function can be deleted if it does not need
+    # to be used.
+    def customPreStep(self):
+        pass
+
+    # Use this function to execute custom code after each simulation time
+    # step is performed. This function can be deleted if it does not need
+    # to be used.
+    def customPostStep(self):
+        pass
 
 
 def main():
@@ -37,10 +37,11 @@ def main():
     world.addSkeleton(ground)
     world.setGravity([0, -9.81, 0])
 
+    # Create world node and add it to viewer
     node = HelloWorldNode(world)
 
-    # Create world node and add it to viewer
-    viewer = dart.gui.osg.Viewer()
+    # create a viewer with background color (red, green, blue, alpha), here: white
+    viewer = dart.gui.osg.Viewer([1.0, 1.0, 1.0, 1.0])
     viewer.addWorldNode(node)
 
     # Grid settings