How rotate the 3D view irrespective to the global Z axis using keyboard?

Question

I have set the "orbit style" setting to "trackball" but it only works when I use the middle mouse button to rotate the view.

The keyboard shortcut does not seems to honor the "orbit style=trackball" setting as numpad 4 / numpad 6 still uses the "turntable" style rotation, and rotate about the global Z axis.

I need to use the keyboard for rotation because I would like to constrain my 3D view rotation to one axis (vertical/horizontal only).

For example, if I

1. set orbit style to trackball
2. hit numpad 7 to align the 3D view to Top View
3. drag middle mouse button left/right

The 3D view will rotate horizontally as desired, however if I hit numpad 4 / numpad 6 instead, it "roll" along the global Z axis

I want to have the same behavior as mouse using keyboard.

I am using Blender 2.76a.

Answer 1

You can roll the view with Shift + Numpad 4 and Shift + Numpad 6.

Edit: Oops. This only works in turntable mode. I misunderstood the question. (Still investigating.)

Edit 2: Sorry. I couldn't figure it out. The best I can offer is this workaround:

Make the model a child of an empty, then rotate the empty 90º on the X axis. From there, you can view the top with Numpad 1 and orbit latitudinally with respect to the object with Numpad 4 and Numpad 6. Once you're done, you can delete the empty and the object will return to its pre-parented orientation.

This is not ideal because it might mess with the mechanics of an armature or other constraints or modifiers.