6.17. Tracking

HitFilm includes multiple options for tracking:

• 2D Feature Tracking: Optical flow and template match tracking for fast feature tracking and stabilization inside HitFilm, described below.
• Planar tracking for advanced roto and camera solving with mocha HitFilm from Imagineer Systems.
• Importing 3D camera tracking data from third party applications including Boujou, SynthEyes, PFtrack and more.

2D Feature Tracking

HitFilm’s 2D tracker is designed for quickly tracking moving features in your videos.

The Track panel is where you control all of your 2D tracking inside HitFilm. The Track panel only displays information if you have a tracker selected on the timeline.

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

A new tracker can be added to any video layer by clicking the + button on the timeline, found to the right of the Tracks section.

This will add a new tracker to the layer, containing a single tracking point, and will automatically switch to the Layer viewer.

*You can rename your trackers to give them more descriptive names. Especially when you have multiple trackers on a layer, this is useful for organization.

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 populated using the Track panel.

Step 1: Track Your Points

The first step is to track points on your video layer. The Track and Layer panels must be visible. They are displayed automatically when a new Track is created, but if they are not currently visible when you want to start tracking, they will need to be selected so they are visible.

*Tracking points are only displayed on the Layer panel. For more information see The Layer viewer.

Tracking Setup

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. 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 clip. 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.

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.

Positioning the Tracking Point

The Layer panel displays your selected layer. The currently selected tracker is 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 red box should be placed around the element you wish to track.

• Search Area: On each frame the green search area will be used to locate the feature area’s new position. It is therefore important that the 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.

Track Controls

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.

Repositioning the Feature Area

During tracking, if the feature you are tracking leaves the frame or becomes untrackable for some other reason, you can reposition the Feature Area without moving the Feature Offset. If this becomes necessary, hold ALT (OPT on Mac), and drag the Feature Area to a new feature that is in frame, or better suited to tracking.

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 Transform 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.

Stabilize

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.

Transform

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.