You can set rotation snap angle increments to show in the Viewer.

To set a rotation increment:

1. Select Settings > Preferences from the MotionBuilder menu bar.
2. From the Preferences window, select Viewer.

   The Viewer default preference settings appear.

   

   Viewer preferences

3. In the 3D Manipulator settings, double-click the Rotation Snap Angle field and enter a value.
4. If you have set a Snap Angle previously, right-click the Snap Rotation button in the Viewer window to see a list of the last five angles set.
   
5. Click one of the angles listed, or click Preferences to open the Preferences window, where you can set an angle.