UM:Ft Reference

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The DVO Tracker is available to use everywhere we have a Shapes layer available. As such, we can draw a shape to define the feature we wish to track and use the result as a Region of Interest matte.




Every Shapes parameter pane includes the new DVO Tracker control parameters as shown in the figures below. The DVO Tracker controls become available once a shape is drawn.



Shape controls and new DVO Tracker controls highlighted



Track Buttons



These buttons start the tracking process. You can track forwards or backwards in a shot, to the shot end or start (respectively) or a frame at a time.


From left to right we have :



Track backwards from current frame to start of shot.


Track backwards one frame from current frame.


Track forwards one frame from current frame.


Track forwards from current frame to end of shot.

Feature Points



The Feature Points button toggles display of the feature points used by the DVO Tracker at each frame.


Feature Points are points inside our shape that are calculated to be good patterns to use when tracking. They are chosen automatically and appear inside the shape we have defined.



Feature Points in green, found inside the defined shape.



Feature Points are chosen dynamically on a frame by frame basis. They are not user selectable or editable.

Transform Buttons



These buttons control what transformations are applied to the shape as we track. If the button is off (white), the selected transformation is not applied.



If no transform buttons are enabled, the defined shape will not move or change at all because no transformations will be applied.


From left to right we have :



Pan X/Y

Enable to calculate X/Y (up/down/left/right) pans.



Enable to calculate feature rotation.


Scale X

Enable to calculate scale changes in the X-axis.


Scale Y

Enable to calculate scale changes in the Y-axis.

Offset Button



The Offset button creates an offset shape from the currently selected shape.


This offset shape can be moved (offset) to a new position in the shot from where new feature points are calculated. The feature points calculated using the offset shape are applied to the original shape. You can re-position an offset shape any number of times in the same shot if required, with any tracking data calculated applied to the original shape. See Offset Tracking.

Smooth Button



Normally, the DVO Tracker will position the transformed shape (x/y,rotation,scale) in single pixel increments. The Smooth button will enable sub-pixel positioning, and cause the track to be re-computed.


This smoothing effect will be visible by switching to the Keyframe Editor tab and viewing the resultant animation graph.



If you turn the Smooth button off before completion, the smooth process will stop and any smoothing done will be reset to its previous state. Once complete, an undo operation will also reset the entire track path to its pre-smoothed state.

Reset Track Points



These buttons allow you to reset all or some of the key-frames created by the tracking process.


From left to right we have :



Reset all track key-frames from current position to start of shot.


Reset all track key-frames.


Reset all track key-frames from current position to end of shot.


The tracker key-frames are shown below the Shapes panel as green diamonds :



Key-frames shown in green, and current key-frame in blue.


Pressing the reset all left button ch-feature-tracker-buttons-reset-leftinclusively). This results in the following key-frame status :



Key-frames after reset all left button pressed.

Image Enhance



Image Enhance will do some image processing on the shot to increase the contrast such that tracking is optimised and a more accurate track calculated. This enhancement is transparent and done in the background (with no visible image changes).


Enabling Image Enhance may be necessary for certain type of media, particularly those with lower contrast or high contrast changes.



Image Enhance will default to on for Log projects.

Other Shapes



This drop-down list lets you apply the tracking data from a previously tracked shape in the shot (in another layer) to the current shape. See Using Other Tracks.

Predict Tracking



The Predict Tracking toggle button lets you carry on the track even if all tracked feature points have moved outside the image frame and tracking has terminated. Turning Predict Tracking on will extrapolate the track to the end (or start) of the shot such that the track is contiguous and smoothly extended. See Predictive Tracking.


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