Tracking Features in the Footage
Now that you know the basics, we can explore the marker settings.
You can modify the tracking settings for markers in two different places: in the Properties Region and in the Tools Region. The settings in the Properties Region will affect the currently selected marker’s tracking settings, while the settings in the Tools Region are the parameters that will be applied by default when you create new trackers.
Tracking settings include various options and values such as what color channel the settings will be tracking, the pattern and search size, if the markers track Location only (this is the one you’ll be using here), and the rotation, scale, and perspective of the features.
One of the options is the Match Type, which is very important! You can set it to match the Keyframe or the Previous Frame. Keyframe will tell Blender to look in every frame for a feature similar to the one you set in the last manual keyframe for the marker. Previous Frame will look for a feature similar to the one in the last tracked frame. Why is this important? Usually, you want to use the Previous Frame option, as a tracking feature can change slightly throughout the video (because of perspective), so it’s better if the tracker adapts to that small change that happens frame by frame; otherwise, at some point in time the feature will be very different from its appearance in the last manual keyframe and the tracker will stop working.
Now it’s time to start tracking! Here are the steps you need to follow to track features:
1. First, create a marker. In the Tools Region, on the Marker tab, click the Add button and then left click over the footage where you want to create the new marker.
Tip
A quicker way to create markers is to press Ctrl + LMB where you want the new marker and it will be immediately placed in that location.
2. Adjust the marker so the pattern area fits the feature you want to follow (maybe a corner or a spot). Scale it up and down with S to adjust it to the feature’s size. In the Track panel, at the top of the Properties Region, look at the zoomed version of the pattern defined by the marker to make sure it’s correct.
3. Track that feature along the footage using the Track Forward and Track Backward features. In the Track panel of the Tools Region, launch the automatic tracking or use Ctrl + T to track forward and Shift + Ctrl + T to track backward.
4. Track frame by frame using Alt + Right Arrow and Alt + Left Arrow. Press L to center the view in the currently selected marker and, in the Marker Display panel of the Properties Region, set the options for what you want to see on the screen (such as the Search Area of markers).
Tip
Sometimes, the feature won’t be visible (imagine that you’re tracking a window in a building in the background and it’s obscured in some frames by a post in the foreground). You can just stop tracking, skip some frames, and start tracking when the feature becomes visible again. A marker will only be evaluated while it has tracking keyframes (either manual or automatic), so if you just skip some frames without tracking it, it will be treated as disabled for those frames.
5. Track the markers one at a time to make sure the tracking is progressing correctly; however, you can track multiple markers at once if you want.
6. Once a marker has been correctly tracked in all parts of the footage where the feature that the marker is following appears, lock it to prevent accidental moves or tracks. In the Track panel of the Properties Region, there are two icons: an eye and a lock. The eye enables and disables the tracker while the lock just makes it impossible to adjust the marker until you unlock it.
Tip
When you press Ctrl + T or Shift + Ctrl + T to automatically track with a marker, tracking will be very fast (depending on your computer and the complexity/size of the pattern Blender is searching for) and almost impossible to follow with the eye. Sometimes that’s good because it will complete the tracking quickly and will stop only when the tracking fails. However, in some situations, even though the tracking doesn’t fail, it’s not correct because it slides little by little on the feature, meaning that the track won’t be exact. What you can do to better monitor the tracking is to go to the Tracking Settings in the Properties Region and, in the Speed option, set it to Realtime or slower. This way, even though Blender can track the feature faster, it will track it at a normal speed so you can see what’s going on throughout the process.
7. Repeat this process with as many features as you can (try to have a minimum of 8 to 10 in every single frame). Press M to mute the video (press it again to unmute) and play the video to see only the markers moving against a black background.
8. Make sure there are no markers going crazy or moving weirdly compared to others. If one or more of the markers are not right, don’t worry; you can come back and adjust them at any time if the camera solution fails.