The Track panel is where you control all of your 2D tracking.
2D tracking is used when you need to track a specific feature in a shot, or to stabilize a shot. It is different to 3D camera tracking, which is used to derive the movement of the live action camera. For information on importing 3D camera tracking data see Importing files.
Both versions of HitFilm 2 include 2D tracking. HitFilm 2 Ultimate is required for 3D camera solving, using the included mocha HitFilm or a 3rd party tracker such as Boujou or SynthEyes.
The tracking process
Tracking is split into two steps. First you track parts of a video layer, then you apply that tracking data to a layer either to stabilize or transform it.
Tracking can only be performed on video layers.
When you track a layer the information is stored in a Tracker on the timeline, under the Track section. A tracker can then contain one or two tracking points, which store the actual animation keyframes.
Creating a tracker
The Track panel only displays information if you have a tracker selected on the timeline.
A new tracker can be added to any video layer by clicking the Insert tracker button on the timeline, found to the right of the Tracks section.
This will add a tracker to the layer, containing a single tracking point.
Trackers can be renamed on the timeline.
Tracking point properties
Tracking points contain several properties which can be edited manually from the Controls panel or timeline. However, these properties will most commonly be controlled indirectly from the Track and Layer panels.
Step 1: Track your points
The first step is to track points on your video layer. To do this you must switch to the Track and Layer panels.
Tracking points are only displayed on the Layer panel. For more information read the Layer panel chapter.
There are several properties that can be adjusted in the Track panel prior to tracking your points.
|•||Type - you can choose between tracking a single point or two points. If you want to track rotation or scale transformation you will need to use the double point option. For simpler position tracking you only need a single point.|
|•||Method - HitFilm has two types of tracking, optical flow and template match.|
The Options button displays advanced technical settings which affect the tracking systems:
|•||Error tolerance - this setting determines when HitFilm will automatically stop the tracking if the accuracy drops below a certain point. A high tolerance setting will cause tracking to continue even when the system is unsure of the results. A low tolerance will cause HitFilm to stop tracking if it is uncertain. The default setting offers a good balance.|
|•||Iterations - more iterations will provide more accurate optical flow tracking but will take longer to process.|
|•||Channels - the template match method can examine the Luminance or RGB channels when tracking.|
|•||Comparison method - template match can use varying methods to identify and track the feature within the search area.|
Optical flow or template match?
Choosing a specific tracking method can affect the quality of your results. Both methods should provide high quality tracks but you may find that certain situations better suit one or the other.
Optical flow observes all movement within the search area, determining the flow of brightness to track the object. This is useful if the tracked feature is repeated several times inside the search area, or if the shape of the tracked feature changes slightly over time. Optical flow can also sometimes continue to track a feature even if it is obscured for a few frames, by continuing to track the overall flow of movement. This method can also have unpredictable results in some circumstances, particularly when tracking small features that are moving rapidly across textured surfaces.
Template match looks for an exact copy of the feature within the search area so can sometimes provide more predictable results. It can also search using the RGB channels as well as the luminance channel.
Positioning the tracking point
The Layer panel displays your selected layer. Tracking points associated with the currently selected tracker are also displayed.
Tracking points consist of three elements:
|•||Feature offset - this central point is used to create the actual transform data that will then be applied to other layers. This enables you to track one area while creating relative keyframes in a different location. The feature offset can be moved outside of the feature and search areas.|
|•||Feature area - this box should be placed around the element you wish to track.|
|•||Search area - on each frame the search area will be used to locate the feature area's new position. It is therefore important that he search area is big enough to cover the movement in the video from frame to frame.|
Positioning the tracking point elements correctly is key to a successful track.
If you are working with two points, note that it is the primary point that determines the position of the track. The secondary point is is used for reference to determine scale and rotation.
Once you have positioned your tracking points you are then ready to begin tracking.
The four track controls are used to track forwards and backwards through the video. You can track frame by frame, or use the play forwards/backwards buttons to track the entire video in the chosen direction.
As HitFilm tracks the video keyframes will be added to tracking points on the timeline. You can stop the track at any time by clicking anywhere in the interface.
Even if you stop the track, any keyframes created up to that point will be retained.
Step 2: Apply to layer
Once you have created tracking data in step 1, you then need to choose what to do with it. This is also done using the Track panel.
|•||Purpose - choose between stabilize or transform.|
|•||Layer - if you select transform as your purpose, you also need to choose a layer to apply the data to.|
|•||Property checkboxes - you can choose which aspects of the track you wish to apply to the layer using the checkboxes. If you want to use rotation and scale tracking you need to select double points in step 1.|
You can stabilize your tracked shot using HitFilm. When the stabilize option is selected, the tracking data will be applied to the source layer. This will transform the layer so that the tracked point remains in the same position in the frame.
You can stabilize based on any point in the frame. If you apply stabilize after tracking a person walking along, the shot will be altered to keep the person perfectly centered in the frame. If you track an immobile background element, the stabilize will eliminate any handheld wobble.
Anchor point keyframes are added to the selected layer, replacing any existing keyframes.
Stabilizing a shot will transform it within the composite shot. This is likely to reveal the edge of the layer as it moves around. To counter this you should increase the scale of the shot so that it fills the frame at all times.
Selecting transform from the purpose menu enables you to then select a different layer. The tracking data will then be applied to that layer.
This is useful if you want a layer to track to a particular part of your video. Perhaps you want to replace a sign, or to track a light flare onto a street lamp. You can apply the tracking data to any layer, including point layers, which can open up exciting visual effects possibilities.
Position keyframes are applied to the chosen layer, replacing any existing keyframes.
Applying tracked transform data to a new Point layer provides many benefits. For example, you can then link multiple items (a 3D light, a light flare effect, a light rays effect etc) to that one point layer and move them as one.
RECAP 2D tracking offers hugely powerful possibilities for visual effects and compositing.