A headless ghost

How did I produce Figure 7?

I repositioned the camera to provide a better view of the center point on the left arm.

I made the head invisible to get it out of the way.

I set the opacity property of the upper body to 30%.  We can now see the shoulder joint through it.

I rendered the left arm as a wireframe drawing instead of a solid drawing.

Now we can see the center point and the 3D axes for the left arm in Figure 7.