Preparing to Analyze

A good analysis result is often footage dependant, therefore you may need to perform object tracking after the initial camera tracking.

Here are some things to keep in mind that can improve your analysis:

• The Analyzer works best when tracking an image sequence that has a moving camera or environment. Action GMasks or mattes should be used to isolate the background and the objects in the scene that have different motions. Masking objects cause them to be ignored in the tracking process. You should also mask any logos or watermarks in your image sequence.
  Note: GMask options are unavailable on Smoke, unless a setup is loaded in Action with an existing Action Gmask node.
• The analysis is based on point-like and corner-like image features. Balls, spheres, lines, and smooth surfaces are not considered.
• Crop out any black areas around your image (such as letterbox areas). When cropping, it is very important to keep the optical centre of the image in the centre, that is, the crop should be symmetrical in both dimensions.
• 3D tracking analyses each frame extensively and with high resolution clips, the process can be lengthy. Unlike 2D tracking, however, you are not required to analyse full-resolution clips. In many cases, analyzing proxies will produce acceptable 3D tracking results quicker than the time that would be required for the full-resolution clips.
• If you have information about the camera that shot the scene you want to track, such as the focal length of the lens and the film back size, it is recommended you specify these details to improve the results of the tracking analysis.

Obtain better tracking results by adding manual trackers

Add manual trackers to produce a more consistent track result. Each tracker consists of an inner reference box, which establishes the reference point for the tracking, and an outer tracker box, which follows the movement of the reference point. You can explicitly choose specific trackable features in the image (see How the Stabilizer Works).

While trackers can be added both pre- or post-processing, it is recommended to do so pre-process if there is going to be a difficult sequence to track. Add trackers post-process to improve the results of the automatic processing. If added post-process, click the Update button.

When tracking, the more track points you have in each frame, the smoother and more accurate the tracking results. 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 add manual trackers:

1. In the Analyzer menu, click the Add 2D Tracker button.

   The Stabilizer tool opens and automatically displays the Analyzer media

2. Click Add Tracker.

   A tracker will appear on the middle of the view.

3. Place the tracker over a trackable feature.

   Add as many as you need to improve the tracking.

   Manually added trackers will be assigned a number, incrementing from the first tracker. Manual trackers can then be selected by either:

   • Selecting them directly on the screen or,
   • Selecting the corresponding Tracker button.
4. Click Analyze.
5. Click Return when done to return to the Analyzer menu.

   The trackers will now be visible in the Analyzer view in a different color from the automatically generated trackers.

Note: Manually added trackers have persistence. They cannot be filtered, and they will not be deleted in a reset. However a tracker can be manually deleted by first selecting it, and in the Fine Tuning section, clicking Delete.