title: vpython 7 with jupyter notebook kernel jump between busy and idle
body: <p>I am trying to run a simple ball moving demo program using vpython 7 on jupyter notebook, however, the ball didn't move smoothly, but like jumping from one position to the next position, there are big delays between frames. I ran the same code in glowscript.org, it demonstrated very smooth motions. After I start the cell, the statue of the jupyter notebook kernel quickly jumps between busy and idle, even if the loop ends, it still jumping. If I interrupt that kernel, the notebook prompt kernel's have died and I have to restart the kernel. I believe this reason results in the delays of the 3D render of the vpython.</p>
  
  <p>I am using Ubuntu 14.04, python 2.7, vpython 7.2.0, jupyter notebook 4.2.3 and chrome.</p>