< Previous | Contents | Manuals Home | Boris FX | Next >
Supervised Tracking
Solving for the 3-D positions of your camera and elements of the scene requires a collection of trackers tracked through some or all of the shot. Depending on what happens in your shot, 7 or 8 may be sufficient (at least 6), but a complex shot, with trackers becoming blocked or going off the edge of the frame, can require substantially more. If the automated tracker is unable to produce satisfactory trackers, you will need to add trackers directly. Or, you can use the techniques here to improve automatically- generated ones. Specific supervised trackers can be especially valuable to serve as references for inserting objects, or for aligning the coordinate system as desired.
WARNING : Tracking, especially supervised tracking, can be stressful to body parts such as your fingers, hands, wrists, eyes, and back, like any other detail-oriented computer activity. Be sure to use an ergonomically sound workstation setup and schedule frequent rest breaks. See Click-on/Click-off mode.
To begin supervised tracking, select the
Tracker panel. Turn on the Create button 
.
Tip : You can create a tracker at any time by holding down the ‘C’ key and left- clicking in the camera view. Or, right-click in the camera view and select the Create Trackers item. In either case you will be switched to the Tracker control panel.
Rewind to the beginning of the shot 
.
Locate a feature to track: a corner or small spot in the image that you could reach in and put your finger on.
Important : Do not select features that shift depending on camera location , such as a reflective highlight or the X formed by two tree branches crossing .
Left-click on the center of your feature, and while the button is down, position the tracker accurately using the view window on the command panel. The gain and brightness spinners located next to the tracker mini-view can make shadowed or blown- out features more visible (they do not affect tracking directly). Adjust the tracker size and aspect ratio to enclose the feature and a little of the region around it, using either the spinner or inner handle.
Adjust the Search size spinner or outer handle based on how uncertainly the tracker moves each frame. This is a matter of experience. A smooth shot permits a small search size even if the tracker accelerates to a higher rate.
Create any number of trackers before tracking them through the shot. You might create and track a batch of 3-6 at a time in a simple shot, or only one at a time on shots requiring more supervision.
Tip : later you'll see how to tell if you have enough trackers using the colored background in the Graph Editor, or in the timebar—if View/Timebar background/Tracker count is turned on.
To track them through the shot, hit the Play 
or frame forward 
button or use the mouse scroll wheel inside the tracker mini-view (scrubbing the time bar does not cause tracking by design). Watch the trackers as you move through the shot. If any get off track, back up a frame or two, and drag them in the image back to the right location. The Play button will stop automatically if a tracker misbehaves, already selected for easy correction.
Supervised trackers have many controls; they are there for a reason. You should be sure to adjust the controls to each specific shot. Usually when people have problems with supervised tracking , it is because they have not configured them at all!
Important! In addition to the more obvious tracker size and search size settings, you should always be sure to select the proper tracker prediction mode on the Track menu.
©2024 Boris FX, Inc. — UNOFFICIAL — Converted from original PDF.