Index: kernel/include/IMP/Vector3D.h
===================================================================
--- kernel/include/IMP/Vector3D.h	(revision 349)
+++ kernel/include/IMP/Vector3D.h	(working copy)
@@ -16,6 +16,8 @@
 {
 
 //! Simple 3D vector class
+/** \ingroup helper
+ */
 class IMPDLLEXPORT Vector3D
 {
 public:
@@ -26,6 +28,9 @@
     vec_[2] = z;
   }
 
+  //! Default constructor
+  Vector3D(){}
+
   //! \return A single component of this vector (0-2).
   Float get_component(int i) const {
     return vec_[i];