The diagram provided is helpful, but I’m wondering if you can fill in some of the blanks around it:
For the position, assuming it is a translation, what are the units?
For the rotation, what does it represent and how are we to apply it? Does it represent the direction in which the user’s face is pointing? I feel like your diagram needs two separate 3D axes to show this – the original one shown in the diagram and the post-rotation axis relative to a 3D head.
Do we rotate the “head” about (0,0,0) before translating it? After?
An explanation (or even better, a code sample with visual output) would be much appreciated. Thank you!