Before you start manual 3D tracking, you should examine the clip closely to determine the points you want to track. The quality of the 2D track has a direct impact on the 3D tracking result, so it is important that you have a strategy for positioning the trackers in the clip sequence. Use the Stabilizer to track and stabilize the clip as accurately as possible. See Tracking and Stabilizing.

For optimum results, each frame in the clip you are tracking must contain at least six track points. In the Stabilizer, this means six trackers are enabled. Also, at least two frames in the clip sequence must have a minimum of eight trackers, and these two reference frames should show the widest camera movement.

When tracking, the more track points you have in each frame, the smoother and more accurate the tracking result will be. As you place the trackers on the image, consider the following guidelines:

• Scatter the trackers by placing them on markings, corners, and shadows in the widest area possible. For example, avoid placing all trackers on the floor; place them on walls and other objects in the scene, as well as on the floor.
• Create a sense of depth by positioning trackers on points that lie in different planes, as well as on points located in the foreground and the background of the sequence.
• Avoid tracking points such as highlights or a point where the foreground and a background object meet, as they do not represent physical 3D points.
• Balance the number of trackers within each frame of the sequence so that as you move through the clip, some points leave the frame and other points appear in the frame. However, maintain a balance so that too many points do not leave or enter the frame at the same time.
• Avoid positioning the trackers in uniform areas or on linear edges where the track points may slide along the edge.

To set up manual trackers:

1. In Action, click 3D Track.
2. From the 3D Tracker Option box, select Manual.

   
   

3. Click Stabilizer to open the Stabilizer menu.

   
   

4. Add trackers to the scene by clicking Add Tracker.

   
   

   NoteYou can track points only on the back clip that you load in Action.
5. Drag each tracker to a position on the image following the guidelines described in Basic Manual 3D Tracking.

   You should have at least six trackers active at any one time, and at least two frames should have eight active trackers.

6. In the Stabilizer menu, click Analyse to process the 2D tracking path and check your result.

   If the tracking is not correct, try standard tracking techniques as described in Tracking and Stabilizing.

7. Click Return to return to the 3D tracking controls.

When you track a pattern that appears to drift or stray, you should set more intermediate trackers in the frames of the sequence, and ensure both the first and the last reference frames are set properly.