About Orient Mode
Orient Mode (View > Orientation > Orient Mode) gives you more viewing capability than the standard spin, pan, zoom. With Orient Mode enabled, you can reorient the view with respect to specific geometry and change the style of view reorientation such as Dynamic, Anchored, Delayed, Velocity, or Fly Through.
Orientation Center
The Orientation Center is displayed by a graphical object that, when clicked with the middle-mouse button, reorients the model in various ways. As you spin, pan, or zoom, the Orientation Center is visible. The Orientation Center is locked at the Spin Center but can be set anywhere in the graphics window when the Spin Center is disabled.
Spin and Pan Constraint
You can constrain spin and pan with respect to a derived vector when the Spin Center is disabled. The vector is derived by placing the Orientation Center on an edge or surface, combined with a drag action; or, if it is already on an edge or a surface, by initiating a drag action on the Orientation Center.
The constraining vector is derived from the object or geometry beneath the Orientation Center, and is either linear to an edge or curve, or normal to a solid face or surface.
You cannot select items when Orient Mode is enabled.