Tracker

Add Tracks

Methods

  • Use the 'Add Track' button in the Tracker Properties panel
  • With the 'Add Tracks" button in the Viewer

    • Verify that the Tracker node's Properties are open to enable the button.

    Button is located at top left corner of Viewer

    Enable button to place tracker on plate

    NOTE: Verify that button is disabled once tracker is placed to prevent other trackers from being placed with subsequent mouse clicks.

  • CTRL + ALT + LMB click in the Viewer

    • Verify that the Tracker node's Properties are open to enable the functionality.

Placement Strategy

  • Identify distinct and contrasting features that span the frame range. Place trackers on such defined locations throughout plate.
  • Aim to track elements in different depth planes throughout scene. This will help with parallax motion.
  • The more stable and accurate trackers that are in place the better it will be for the camera tracker.
  • Discard any questionable tracks.

Key Tracking Factors

  • Verify that you start on Frame 1 or be cognizant of the frame on which the tracker is placed.
  • Defined tracking points need to stay visible within the frame over the course of the frame range.
  • Highly detailed areas with high contrast can serve as good elements for tracking.
  • Note that detailed areas with parallax movement can lead to errors in tracking. For instance, tracking elements on the sides where objects in scene overlap other objects as a camera dollies in or out can lead to such confusion for the tracker.

Tracker Structure

  • Center of track
  • Middle square: Tracking zone; this what Nuke will look for when tracking. This area basically becomes a 'reference target'.
  • Outer square: Search zone that Nuke will look at to identify the 'reference target'.
    • Moderate the size of this square so as not to overwhelm the computation of the tracking and to mitigate the potential of the tracker attempting to find the 'reference target' elsewhere throughout the plate.

Track & Monitor

Depending on where along the frame range the tracker was placed, use the controls at top of Viewer to 'Track to End', 'Track to Start', or use on of the other tracking options to initiate the tracking of a tracker.

Search Zone Monitor

When tracking, note the larger magnified view of the search zone, located at the top left corner of the Viewer.

This is the monitor to focus on when tracking to confirm that the intended 'reference target' stays consistently in the middle of the monitor. Confirming this over the course of the frame range signals a good track. Of particular attention is the stability of the track's center point.

Tracking documented with keyframes highlighted on timeline.

Generated keyframes for trackers can be deleted by using the controls at top right of Viewer, including 'Clear Backward', 'Clear Forward', and others.

Tracking Occlusion

In cases where a tracker loses tracking capabilities by occlusion from other scene elements, clear invalid tracking keyframes, offset tracker at point of last good track, and continue tracking to account for missing keyframes.

Example Scenario

  1. Tracker starts well from Frame 0 to Frame 20, but remaining frames are invalid due to occlusion.
  2. Use 'Clear Forward' from Frame 20.
  3. Set scrubber to Frame 20.
  4. Offset tracker center, reference target, and search zone using CTRL + LMB drag to position it to a nearby trackable area (preferably on same depth plane). Yellow line between trackers denotes offset.

    5. This is actually continuing to preserve the coordinates of the original tracking position, but using the offset location to do the actual tracking since the original tracking location was occluded.

    This offset distance is noted in the Tracker Properties for this specific tracker.

  5. Continue tracking with 'Track to End' to capture keyframes on remaining frame range.