Understand object booting

When objects are active in the Tracking panel, Tracker undergoes a process known as booting whenever a set of unlabeled reconstructions first appears in the 3D View. Booting is the process which enables an object to begin tracking. For efficient booting, we strongly recommend that each object has a unique pattern of markers (see Understand object evaluation) and that you set the Entrance Threshold appropriately. This is particularly helpful in cases of frequent occlusion and results in more consistent tracking with fewer dropped frames.

Entrance Threshold

The Entrance Threshold is the minimum proportion of markers in an object that must be visible to successfully boot that object. You can set it between 0.00 and 1.00, with 1.00 representing 100% of the markers on that object.

If the Entrance Threshold is low, it is easier to boot the object, but more likely that pose of an object will be initialized incorrectly, potentially resulting in the use of markers that are actually on another object (ie, object swapping). For example, if you have a 10-marker object with an Entrance Threshold of 0.3 or lower, tracking can start as soon as any three markers are detected in the correct pattern (three is the minimum number required to track). This means that the object could be confused (and be considered similar) with any other object that has the same or similar pattern of three markers, regardless of the other markers on that object.

If the Entrance Threshold is high, it can be more difficult for the system to boot an object, particularly if the object geometry makes it too difficult to see a high enough proportion of markers simultaneously. This may be the case for an object resting on the ground, for example: any markers on the underside may not be visible to the cameras. However, this has the added benefit of conducting a more thorough evaluation of an object's marker geometry when assessing similarity. As such, you may not want the entrance threshold for object tracking to be the same as the entrance threshold used for object evaluation.

Configuring the Entrance Threshold

In Tracker, you can set the Entrance Threshold in the following ways:

• Globally, for all objects in the Object Tracking section of the Processing panel

  

• Locally, for an individual object using an object preset (see Work with objects).

  Note, you do not need to set any filtering if you only want to control specify an Entrance Threshold for that object.