Tracker panel
The Tracker button in the Effect Stack Manager brings up the tracker controls. Trackers can be used to perform various tasks in PFClean, such as assisting with Stabilization or Rig Removal, animating masks and paint strokes or assisting optical flow calculations. The Tracker Panel operates in a similar way to the Mask panel: trackers can be created, edited and activated in different effects.
The Tracker panel is divided into three sections. On the left is the Tracking Window, showing the position of the current tracker in the Cinema window. The Parameters panel contains the parameters for the current tracker, and the Tracker List on the right displays all available trackers along with controls for adjusting and tracking.
When trackers are created, they are activated in the current effect by default. Alternatively, trackers can also be created in the base clip and then activated where necessary in other effects. Deactive trackers are greyed-out in the tracker list.
Currently, trackers can be used to perform the following functions:
Masks and groups of mask vertices can be attached to trackers to assist with mask animation,
Paint strokes can be attached to trackers to assist with paint stroke animation,
The Stabilize effect can make use of trackers when estimating motion between frames.
The Remove Rig effect can use trackers to assist with motion estimation and aligning a clean plate clip with the working clip.
The Fix Frame effect can use trackers to assist with optical flow calculations when interpolating data between frames.
Creating and Positioning Trackers
Trackers are created by clicking the New button on the right of the tracker list. By default, newly created trackers are activated in the current effect, and are positioned in the centre of the Cinema viewport.
The outer dotted line around the tracker represents the search area, and the inner box the actual tracking window. The contents of the tracker window are also shown in the Tracking Window control. The tracker displays its current X/Y position and similarity value, which corresponds to the tracking accuracy in the current frame (a value of 1.0 indicates full accuracy, and will appear whenever the tracker is positioned by hand).
The tracker can be positioned by clicking and dragging with the left mouse button inside the search area in the Cinema, or by clicking and dragging inside the Tracking Window control. The edges of the search area and tracking window can also be adjusted in the Cinema using the left mouse button.
At the centre of the tracking window in the Cinema is a small red dot that represents the actual position of the tracker. The tracking window should be adjusted so that it contains enough texture to track; If the window is placed over a very flat are with little variation, there may not be enough information to ensure an accurate track. The tracking window should not be too large, however, if the point being tracked is undergoing significant rotation or scaling. In this case, the contents of the tracking window may change too much due to perspective effects for the tracker to be accurately updated from frame-to-frame.
In situations where the central tracking point must be placed in an area that does not contain enough texture, the window can be offset to somewhere in the frame that does. To do this, hold down the Control key when positioning the tracker. This will mean that only the tracking window is adjusted, whilst the red dot (which indicates the actual tracker position) is kept in the same place. When doing this, the Tracking Offset parameters will be updated to indicate the offset that has been applied.
Trackers can be positioned by hand in any frame, and their position will be interpolated between the keyframes where necessary. Their X and Y position curves are available in the F-Curve Editor and Dope-Sheet.
Tracking Forwards and Backwards
Trackers can be tracked forwards and backwards from any frame by clicking the tracking buttons underneath the Tracker List:
From left to right, the buttons correspond to: Track backwards by many frames, Track backwards by one frame, Track forwards by one frame, and Track forwards by many frames. As tracking progresses, the tracker position will change in the Cinema and the contents of the Tracking Window will update accordingly.
When tracking forwards or backwards by many frames, tracking will stop once the tracker reaches a frame where the tracker has already been keyframed. Every time tracking is performed, the initial contents of the Tracking Window will be stored (the 'reference tracking window') and compared against the window in each frame. Tracking will also stop when the similarity of the two windows is below the Failure Tolerance, defined in the Parameters (see below). Tracking can be stopped manually by pressing the Esc key, or by clicking the Stop buttons that appear underneath the Tracker list.
Tracking Window
The Tracking Window:
displays image data at the current tracker position. The position of the tracker can be adjusted by clicking and dragging inside the Tracking Window using the left mouse button, as well as by moving the tracker in the Cinema.
The Pos boxes show the current tracker position in pixel coordinates, where (0,0) corresponds to the bottom-left of the image. The Sim box displays the similarity value for the current frame, which is a measure of the similarity between the tracking window in the current frame and the 'reference tracking window' when the feature was tracked. A similarity of 1.0 is an exact match, and lower values indicate a poorer match. When positioning a tracker by hand, the similarity value will be set to 1.0
The C button can be used to automatically centre the tracker over a tracking marker:
Auto-centring works best when there are significant colour differences between the outside edge of the tracking window and the inside, such as in the case show on the left. Clicking the C button several times will improve the tracker position incrementally until a stable point is reached.
Parameters
The Tracking parameters are shown below:
The parameters define how each tracker will be tracked between frames. Each tracker can have its parameters adjusted independently.
The Channels buttons describe which of the red, green and blue channels will be used to track. In situations where one or more channels are significantly corrupted by noise or grain, they can be switched off to improve tracking accuracy.
The Window Update buttons are used to define how the 'reference tracking window' is updated during tracking. The default option is Starting Frame, which indicates that the reference window is only updated when tracking starts. Other options are Every Frame to update the window at every frame, or Above Tolerance, which will only update the reference window when the similarity is above the Window Tolerance. The Window Update options can be useful when track large trackers in situations where there are moderate perspective effects or rotation/scaling.
The Failure Mode buttons describe the behaviour of the tracker when the similarity between the 'reference tracking window' and the current tracking window is below the Failure Tolerance level. The available actions are Stop Tracking, or Predict Position which will attempt to predict the position of the tracker given its positions in previous frames. This can be used to help tracking features that are partially occluded in some frames.
The Tracking Offset parameter contains the current offset between the tracking point and the tracking window. It can be adjusted using the available edit boxes or by holding the Control key whilst dragging the tracker position in the Cinema window.
When the Blur Window or De-Flicker buttons are pressed, the contents of the tracking window will be blurred or de-flickered before the similarity is measured and compared against the Failure Tolerance. This can be useful in clips that contain significant noise or grain, or brightness fluctuations. Note that these changes will not be apparent in the Tracking Window panel of the interface, but are instead applied internally where necessary.
The Reset button will reset the tracking parameters to their default values.
The Tracker list
The Tracker List contains all the currently available trackers, along with editing and viewing controls:
Clicking on a tracker in the list will select it, allowing the tracker to be positioned in the Cinema window or tracked. Trackers that are not active in the current effect will appear greyed-out in the list.
Double-click with the left mouse button in the Name column to rename a tracker. Double-clicking in the Colour column will display a colour chooser window to select the colour of the tracker window boundary in the Cinema.
The Start Frame and End Frame columns contain the start and end frame of the tracker, and the Effects column lists all the effects in which the tracker is active.
Clicking the New button will create a new tracker, positioned at the centre of the Cinema viewport.
Clicking in the A column will activate or deactivate the tracker in the current effect. A checkmark in this column indicates whether a tracker is active in the current effect. Trackers cannot be activated in the base clip.
The All/None button is used to select all or none of the trackers in the list.
Clicking the Remove button will remove the current keyframe (if one exists), and the R- and R+ buttons will remove all keyframes before or after the current frame.
Clicking the Del button will delete all currently selected trackers.
Trackers can be tracked forwards and backwards from any frame by clicking the tracking buttons underneath the Tracker List:
From left to right, the buttons correspond to: Track backwards by many frames, Track backwards by one frame, Track forwards by one frame, and Track forwards by many frames. As tracking progresses, the tracker position will change in the Cinema and the contents of the Tracking Window will update accordingly.
The In and Out buttons can be clicked to set the in/out frames for the selected tracker to the current frame. The in/out frames can also be adjusted by editing the values in the boxes, and reset by clicking the R reset buttons.
The Show Trackers button will toggle display of trackers in the cinema. The Show Search button can be used to show or hide the search rectangle, so only the tracking window is displayed, and the Show Path button can be used to show or hide the tracker path in other frames, which is shown as a yellow line in the Cinema.