few corrections

examples/dynamics/control/attractor_point.py

@@ -22,6 +22,7 @@ robot = prl.robots.RRBot(sim)
 robot.disable_motor()           # disable motors; comment the `robot.set_joint_torques(torques)` to see what happens
 robot.print_info()
 robot.change_transparency()
+world.load_robot(robot)
 
 # define variables
 link_id = robot.get_link_ids('hokuyo_link')         # the link we are interested to

examples/dynamics/control/gravity_compensation.py

@@ -22,6 +22,7 @@ robot = prl.robots.RRBot(sim)
 robot.disable_motor()       # disable motors; comment the `robot.set_joint_torques(torques)` to see what happens
 robot.print_info()
 robot.change_transparency()
+world.load_robot(robot)
 
 
 # run simulator

examples/dynamics/control/no_forces.py

@@ -22,6 +22,7 @@ robot = prl.robots.RRBot(sim)
 robot.disable_motor()       # disable motors
 robot.print_info()
 robot.change_transparency()
+world.load_robot(robot)
 
 
 # run simulator

examples/kinematics/inverse/moving_sphere.py

@@ -19,6 +19,7 @@ world = BasicWorld(sim)
 # create robot
 robot = KukaIIWA(sim)
 robot.print_info()
+world.load_robot(robot)
 
 # define useful variables for IK
 dt = 1./240
@@ -61,7 +62,7 @@ for t in count():
     else:
         J = robot.get_linear_jacobian(link_id, q=q)[:, qIdx]
 
-    # Pseudo-inverse
+    # Pseudo-inverse: \hat{J} = J^T (JJ^T + k^2 I)^{-1}
     Jp = robot.get_damped_least_squares_inverse(J, damping)
 
     # evaluate damped-least-squares IK
@@ -72,5 +73,4 @@ for t in count():
     robot.set_joint_positions(q, joint_ids=joint_ids)
 
     # step in simulation
-    robot.step()
     world.step(sleep_dt=dt)