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.