Moving the cursor with the left mouse button held down rotates the model. The rotation is in the direction of the mouse motion. The rotation is based on a trackball algorithm that intersects the cursor position with an imaginary sphere surrounding the model. The conversion from cursor motion to change in angle includes the Rotate Speed Factor on the 3D Control property page. Higher factors result in more rapid movement.
Holding down a modifier key---Alt, Control, or Shift---while rotating with the left mouse constrains the motion to rotation about an axis in model space.
A separate motion display style can be used for lattices while interactive rotation is underway.
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