2017

Table Of Contents
Object Tracking (page 663)
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) (page 718).
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.
648 | Chapter 15 Compositing in 3D Space with Action