The 3d free-rotation for this view camera is a traditionally awkward way (in my opinion) for rotating. I've used different 3d modeling applications, few that do it this way, but I never liked it. I think the early Photoshop 3d viewport used this, but now does something else. Lightwave modeler always had one of the best free-rotation cameras.
Off-hand, I don't remember what that rotation equation is to be most effective.
Off-hand, I don't remember what that rotation equation is to be most effective.