title: Error when I try to assign triangles in open3D
body: <p>i'm trying to do this:</p>
  <pre><code>mesh = o3d.geometry.TriangleMesh()
  mesh.vertices=o3d.utility.Vector3dVector(vertices)
  mesh.triangles=o3d.utility.Vector3dVector(triangles)
  </code></pre>
  <p>but i got this error:</p>
  <pre><code>TypeError: (): incompatible function arguments. The following argument types are supported:
  1. (self: open3d.open3d_pybind.geometry.TriangleMesh, arg0: open3d.open3d_pybind.utility.Vector3iVector) -&gt; None
  
  Invoked with: geometry::TriangleMesh with 3400 points and 0 triangles., std::vector with 6768 elements.
  Use numpy.asarray() to access data.
  
  Did you forget to #include ? Or ,
  , , etc. Some automatic
  conversions are optional and require extra headers to be included
  when compiling your pybind11 module.
  
      vertices is a numpy array with shape (3400,3)
      and triangles is also a numpy array with shape (6768,3)
  </code></pre>
  <p>thanks</p>