import_pdb.py

        atom_mesh.update()
        new_atom_mesh = bpy.data.objects.new(atom[0], atom_mesh)
        bpy.context.scene.objects.link(new_atom_mesh)

        # Now, build a representative sphere (atom)
        current_layers=bpy.context.scene.layers

        if atom[0] == "Vacancy":
            bpy.ops.mesh.primitive_cube_add(
                            view_align=False, enter_editmode=False,
                            location=(0.0, 0.0, 0.0),
                            rotation=(0.0, 0.0, 0.0),
                            layers=current_layers)
        else:
            # NURBS balls
            if use_mesh == False:
                bpy.ops.surface.primitive_nurbs_surface_sphere_add(
                            view_align=False, enter_editmode=False,
                            location=(0,0,0), rotation=(0.0, 0.0, 0.0),
                            layers=current_layers)
            # UV balls
            else:
                bpy.ops.mesh.primitive_uv_sphere_add(
                            segments=Ball_azimuth, ring_count=Ball_zenith,
                            size=1, view_align=False, enter_editmode=False,
                            location=(0,0,0), rotation=(0, 0, 0),
                            layers=current_layers)

        ball = bpy.context.scene.objects.active
        ball.scale  = (atom[3]*Ball_radius_factor,) * 3

        if atom[0] == "Vacancy":
            ball.name = "Cube_"+atom[0]
        else:
            ball.name = "Ball (NURBS)_"+atom[0]
        ball.active_material = atom[1]
        ball.parent = new_atom_mesh
        new_atom_mesh.dupli_type = 'VERTS'
        # The object is back translated to 'object_center_vec'.
        new_atom_mesh.location = object_center_vec
        atom_object_list.append(new_atom_mesh)

    print()


    # ------------------------------------------------------------------------
    # DRAWING THE STICKS


    if use_stick == True and all_sticks != []:

        # Create a new material with the corresponding color. The
        # color is taken from the all_atom list, it is the last entry
        # in the data file (index -1).
        bpy.ops.object.material_slot_add()
        stick_material = bpy.data.materials.new(ATOM_PDB_ELEMENTS[-1].name)
        stick_material.diffuse_color = ATOM_PDB_ELEMENTS[-1].color

        vertices = []
        faces    = []
        dl = 0.2

        i = 0
        # For all sticks, do ...
        for stick in all_sticks:

            # What follows is school mathematics! :-)
            v1 = all_atoms[stick.atom2-1].location
            v2 = all_atoms[stick.atom1-1].location

            dv = (v1 - v2)

            n  = dv / dv.length
            # m  = v1 - dv / 2.0  # UNUSED

            gamma = -n * v1
            b     = v1 + gamma * n
            n_b   = b / b.length

            loops = int(dv.length / dl)

            for j in range(loops):

                g = v1 - n * dl / 2.0 - n * dl * j

                p1 = g + n_b * Stick_diameter
                p2 = g - n_b * Stick_diameter
                p3 = g - n_b.cross(n) * Stick_diameter
                p4 = g + n_b.cross(n) * Stick_diameter

                vertices.append(p1)
                vertices.append(p2)
                vertices.append(p3)
                vertices.append(p4)
                faces.append((i*4+0,i*4+2,i*4+1,i*4+3))
                i += 1

        mesh = bpy.data.meshes.new("Sticks")
        mesh.from_pydata(vertices, [], faces)
        mesh.update()
        new_mesh = bpy.data.objects.new("Sticks", mesh)
        bpy.context.scene.objects.link(new_mesh)

        current_layers = bpy.context.scene.layers
        stick_cylinder = DEF_atom_pdb_build_stick(Stick_diameter, dl, Stick_sectors)


        stick_cylinder.active_material = stick_material
        stick_cylinder.parent = new_mesh
        new_mesh.dupli_type = 'FACES'
        atom_object_list.append(new_mesh)


    # ------------------------------------------------------------------------
    # SELECT ALL LOADED OBJECTS
    bpy.ops.object.select_all(action='DESELECT')
    obj = None
    for obj in atom_object_list:
        obj.select = True

    # activate the last selected object (perhaps another should be active?)
    if obj:
        bpy.context.scene.objects.active = obj

    print("\n\nAll atoms (%d) and sticks (%d) have been drawn - finished.\n\n"
           % (Number_of_total_atoms,Number_of_sticks))


    return Number_of_total_atoms