If the initial auto tracking does not give desired results, you can use some or all of the Filter options to calibrate and refine your track analysis. These procedures are not necessarily required, but depending on your image and the initial tracking, may give better tracking results.

To fine-tune the 3D auto track:

1. Use the Quality slider to adjust the number of good trackers kept. The higher the quality setting, more low quality trackers are selected, such as trackers that drift off their initial reference point. Click Delete to delete the selected trackers.

   
   

   Trackers of lower quality may hinder the accuracy of the camera tracking.

   NoteAfter you have made a change that requires the 3D tracking analysis to be refined or calibrated, notice that the LED next to the Refine and Calibrate buttons turns yellow. This signifies that a Refine or Calibrate is required, but you do not have to perform it until you have completed your tracker selections.
2. Adjust the Short slider to select short duration trackers, that is, trackers that only track a feature for a few frames. Click Delete to delete the selected trackers, leaving the longer duration trackers intact.
3. You can manually select and delete trackers from the image that you feel are not tracking properly. Do one of the following:
   • To select an individual tracker, click the tracker, and then click Delete.
   • To select multiple trackers in the same area, Ctrl-drag a selection box over a series of trackers, and then click Delete.
   • To add another tracker to a multiple selection, Shift-click the tracker, and the click Delete.
   • With Delete mode selected in the Edit Mode box, select trackers in the image.
4. If you want to add a tracker manually, enable Add and click an area of the image to track from this area automatically.

   
   

   A tracker may or may not be added, depending on the ability of the track analysis algorithm to find an appropriate feature to track in this area.

5. If the analysis creates different trackers that refer to the same feature in the image, you can link these trackers. Press Shift and select two or more trackers from the image, and then click Link.

   For example, an element leaving the scene at frame 28 and returning at frame 50 may result in two different trackers attached to the same element in the image. In this case, select the trackers and click Link to teach the algorithm that these trackers are related to the same feature in the scene.

To refine or calibrate the 3D track:

1. Depending on the changes you have made, you can choose to refine or calibrate the 3D track. Do one or both of the following:
   • Click Refine.

   
   

   (a) Refine button  (b) Pixel Error value  

   The track analysis uses the current results as a starting point, and refines from this point.

   Click Refine again to stop the process once an acceptable pixel error value is reached. The pixel error value is a representation of the distance of the 2D tracks from the computed 3D points.

   TipThe refine process is footage-dependant, so your acceptable pixel error value may change depending on what is tracking. Since the refine process continues until you stop it, as a general rule, if the pixel error value does not change for a length of time (for example, 30 seconds), you can stop the refine process. The lower the pixel error value, the more accurate the reconstructed track is.
   • Click Calibrate.

   
   

   NoteThe calibrate operation deletes all previous 3D points and starts over based on the new information. Depending on your footage, and how many trackers you added, deleted, or linked, multiple calibrations may yield different results.